Witness Marks, Sanding Scratches, and other issues that crop up when trying to produce a superb finish...

[hughie]

Well, it would be nice to see more people's work and see where mine falls within the spectrum. But, I think I've learned a few things in this thread, and will be able to cut down my time and effort sanding, but still generally achieve the same results.

I think most of my issue is the amount of time. If I can cut it in half or more, and do hand sanding for the last grit or two, to really clean up any radial scratch marks or anything like that, then I think I'll be happy. Maybe I'll get to a point where I enjoy it too.

For these first two pieces of holly, though, after having gone through this thread and process, I believe I am satisfied. I spent a ton of time on the second one, but it was all for the learning. Its better than the first, which actually was pretty good given my new understanding. The next several should go faster, and I am hoping sanding will be less of a hassle.

I guess the simple answer is work on your tool technique so you dont need as much sanding. I realize this is easy to say and often depends on others, along with investment in time, if not money as well. Things we all dont have enough of at the right time, but at the end of the day it will pay handsomely. But your eye is fine and you a great feel for form and shape so all is not lost. So you have come far and now the journey asks more of you. It could be worse, the first day where everything aint working and the mountain is very steep..

 

[hughie]

@hughie Those are some interesting sanders. I remember trying to figure out how to make a low profile one a while back and couldn't figure out what parts to use. Do you have a recipe you recommend?

I knocked up an article on a DIY sander out of Redgum, a skate wheel and some threaded rod.

 

[robo hippy]

In the middle of sanding out bowls for the only show I do any more. On a whim, I decided to skip the 150 grit and went straight from 120 to 180. I will not be doing that again. The old formula used to be half the grit from the previous grit and add that on, so half of 80 is 40, so the next grit is 120. I know from experience how long it takes to remove 80 grit scratches with 120, and ALWAYS to to 100, then 120. It does save some time....

robo hippy

 

[James McCall]

In the middle of sanding out bowls for the only show I do any more. On a whim, I decided to skip the 150 grit and went straight from 120 to 180. I will not be doing that again. The old formula used to be half the grit from the previous grit and add that on, so half of 80 is 40, so the next grit is 120. I know from experience how long it takes to remove 80 grit scratches with 120, and ALWAYS to to 100, then 120. It does save some time....

robo hippy

I wonder how much of it is that the more grits you use, the more fresh sandpaper you use. Sometimes I think it's not that I need to add more grits but just be willing to throw out sandpaper a little sooner.

 

[James McCall]

Though now that I say that, what better way to ensure using enough fresh sandpaper paper than adding grits, so maybe a pointless distinction

 

[Raif Harik]

I knocked up an article on a DIY sander out of Redgum, a skate wheel and some threaded rod.

@hughie I'm sorry I don't follow. I was wondering about the free spinning sanders in you photos. Like, if you could explain how you made them, source the parts and any "lessons learned" that would be great. If you are feeling ambitious, maybe start a new thread about it.
Thanks

 

[John K Jordan]

the more fresh sandpaper you use.

Years ago I made the observation that when the sandpaper I use (Klingspor Gold on a heavy cloth backing) quit working so well it was usually not worn but just clogged with fine sawdust. (I mostly sand by hand with 320 and 400, occasionally 240) I started brushing it with a stiff plastic brush then found out that wiping it against my work jeans worked as well. That often kept me from wasting perfectly good sandpaper. Works for 600 and 800 too (Indasia Redline Rhynowet).

I don't know if that will work as well with other types of sandpaper or if the grit on some actually wears. And I have no idea about disks rotated on a drill. Don't do that.

I also wet sand, usually with "danish" oil, but just throw the piece away after that gets less effective.

 

[Steve Tiedman]

I have a big rubber sanding belt cleaning block that I use to clean off hand sanding sheets. Works well.

I buy Klingspor 2" wide "shop rolls" on J-weight cloth back. It's flexible like denim, easy to work with. I've got up to 400 grit, maybe even a 600 grit roll. I've bought their bargin boxes in the past but they contained too much heavy X-weight cloth sandpapers. Way too stiff for my liking.

 

[Marc Banka]

Joining in late here after enjoying the various solutions to problems we all have. So, let me share my solutions, or at least the few methods that have solved the problems for me.

Sharp tools make a difference, as has been stated. For bowl turners, where tear-out is a big issue, I strongly suggest learning the 40-40 gouge, either the pure form or jig sharpened ( I use the wolverine). My favorite is the oneway mastercut 5/8 gouge. Wonderfully deep, wide flute.

Lighting is key. You can’t fix what you can’t see. You need two lights, a softer broad light like the Powermatic or Laguna head mounted lights. Soft and broad, so good for general lighting also known as fill light. Second main light is a point source light. Single bulb, focus able, with barn doors or a snoot to keep the light out of your eyes. Station the hard mainlight near the tailstock end about eye level of so to provide light across the bowl exterior roughly perpendicular to the concentric scratches. Adjust the fill light to taste. It will give general,light, but hide the scratches. Find the mix/ratio that’s most comfortable and effective. For interiors I find having the mainlight low at the backside of the lathe illuminates the scratches on the back inside of the bowl. Because the mainlight is a high quality point light it acts just as taking the piece out in the direct sunlight.

Then is sanding methods and materials. Use the best sandpapers. To me best doesn’t mean the longest lasting or the cheapest. I want the sharpest with a soft edge. I tried out one of the latest greatest papers, with a plastic backing. Nice abrasive all the way to 2000 grit. Problem is, the edge of the disk puts 120 grit sized scratches in my finished work! I like Norton products. Papers and disks are the sharpest I’ve found.

One needs to sand in two directions evenly and carefully. I read about finding scratches late in the process and pondering the size of scratch, and which grit you need to go back to. Such a waist of time! You might nail it, probably not. Anyway, way you’ve spent time sanding that may not be needed. Remember, none of us likes to sand.

I usually start with 120 to clean any damage. Lathe on at 750 hand held paper for tool marks/lines and any damaged grain. Lots of concentric scratches. ALL scratches are concentric. Switch to a disc sander, still 120, lathe still at 750. I use a cable drive sander, so very light weight, can hold with a pencil grip. Not hogging wood, not much pressure. Remove ALL of the concentric scratches, replacing them with more angled marks. With the aforementioned lights it is easy to see that only scratches are those caused by the disc.
This way it’s a binary thing. You either have concentric scratches or you don’t.
Move to 180 hand held paper. Again make ALL scratches concentric. Then 180 disc to replace concentric scratches with the angled lines from the disc.
Continue till your final,paper, whatever that is. The only scratches will be from that last grit. For me, that’s 2000.

This might seem laborious, but once one gets the feel for it will find that it doesn’t take that much time. The best things is that you wont have to get back in to whatever grit you think is at fault.

The most important part of a great finish is great surface prep.

My $.02

 

[hughie]

Years ago I made the observation that when the sandpaper I use (Klingspor Gold on a heavy cloth backing) quit working so well it was usually not worn but just clogged with fine sawdust. (I mostly sand by hand with 320 and 400, occasionally 240) I started brushing it with a stiff plastic brush then found out that wiping it against my work jeans worked as well. That often kept me from wasting perfectly good sandpaper. Works for 600 and 800 too (Indasia Redline Rhynowet).

I don't know if that will work as well with other types of sandpaper or if the grit on some actually wears. And I have no idea about disks rotated on a drill. Don't do that.

I also wet sand, usually with "danish" oil, but just throw the piece away after that gets less effective.

yeah there seems to be a few brands that will work with this, but its not universal, I use Astra Dot on my inertia sanders.
Lol I also wet sand with Danish Oil, started doing it a few years ago.

 

[hughie]

@hughie I'm sorry I don't follow. I was wondering about the free spinning sanders in you photos. Like, if you could explain how you made them, source the parts and any "lessons learned" that would be great. If you are feeling ambitious, maybe start a new thread about it.
Thanks

Ok I think I should, thought I has some images but could not locate them. I probably have made 15-20 of them over the years.

 

[robo hippy]

I do pay close attention to how my abrasives are cutting. Most of the time, this is by noting how much dust is coming off as I sand. The rubber sticks can "refresh" your abrasives, but eventually they all will get to the toss it away stage. Learning when this time comes is a big part of sanding out your bowls. I have yet to try the Cubitron abrasives from 3M. Currently I use the blue discs from Vince. They outlast any other abrasive I have used by far. I can generally get several bowls, like 10 inch diameter by 3 deep bowls out of one set of discs. The LDD soak really helps them last longer too. Some of the loss of cutting efficiency comes from clogging. The LDD soak helps reduce that. The rest of the cutting efficiency comes from the abrasive getting used and the particles get dull, and there is no repair for that.

robo hippy

 

[Jon Rista]

I guess the simple answer is work on your tool technique so you dont need as much sanding. I realize this is easy to say and often depends on others, along with investment in time, if not money as well. Things we all dont have enough of at the right time, but at the end of the day it will pay handsomely. But your eye is fine and you a great feel for form and shape so all is not lost. So you have come far and now the journey asks more of you. It could be worse, the first day where everything aint working and the mountain is very steep..

Yeah, I agree, better tooling will lead to less sanding effort. I am indeed working on it. I'm better now, than I was six months ago, for sure. I need some better tools in some cases, and better handling of them in others, still. In six months, I hope to be as much better then, as I am now compared to six months ago. At least I'm not at the foot of the mountain! (The peak is still a ways off, though, I think! )

I also think, I'm much pickier than the average turner, and I am demanding more of myself, than the average turner might demand of themselves? I've decided to simplify my sanding process a bit as a result, and not be too concerned about how things look right in the "middle" of the process, and be more concerned about how I start (that first grit, and truly getting rid of any tool marks, tearout, etc.) before continuing, and then spending the necessary time with the final grit (and maybe other things like fine 3M pads and the like) to really finesse the final result.

 

[Jon Rista]

In the middle of sanding out bowls for the only show I do any more. On a whim, I decided to skip the 150 grit and went straight from 120 to 180. I will not be doing that again. The old formula used to be half the grit from the previous grit and add that on, so half of 80 is 40, so the next grit is 120. I know from experience how long it takes to remove 80 grit scratches with 120, and ALWAYS to to 100, then 120. It does save some time....

robo hippy

One of the sanding tips I heard early on was "Never skip a grit!" and I've tried to follow that. At least, when I pick a starting point, I don't skip from that point on. I honestly do kind of fear 60, 80, 100, 120 grits these days. I guess once I get to 150, 180, things start to get better, but those lower grits, I feel like they just SHRED, and...I've never really liked that.

Each grit is supposed to be 50% finer than the previous, or close enough. So going from 180 to 240, the 240 will cut into half the depth of the 180 scratches, at least so the theory goes. Then 320 would cut half way into the 240 scratches, 400 half into 320, 600 half into 400, etc. Or, pick your starting point and go from there...80->100 should result in 100 cutting half way into the 80 grit scratches.

 

[Jon Rista]

Years ago I made the observation that when the sandpaper I use (Klingspor Gold on a heavy cloth backing) quit working so well it was usually not worn but just clogged with fine sawdust. (I mostly sand by hand with 320 and 400, occasionally 240) I started brushing it with a stiff plastic brush then found out that wiping it against my work jeans worked as well. That often kept me from wasting perfectly good sandpaper. Works for 600 and 800 too (Indasia Redline Rhynowet).

I don't know if that will work as well with other types of sandpaper or if the grit on some actually wears. And I have no idea about disks rotated on a drill. Don't do that.

I also wet sand, usually with "danish" oil, but just throw the piece away after that gets less effective.

I do this too. I mostly use Norton, or Klingspor paper backed (I really want to try this cloth backed Klingspor Gold though...), and while the grit does seem to wear, it usually doesn't wear as fast as it seems. I tend to wipe clogged sandpaper on my jeans, which works quite well!

I have found, though, that at the higher grits, the black wet/dry sandpaper, from 400 grit on up, and pretty much anything over 1200 regardless of brand, when it clogs, it clogs differently, and usually I can't get the junk that's clogging off. So I have taken to using smaller pieces, and swapping them out more frequently. The smaller pieces make me use up every bit of unused grit on the piece before getting another, and generally keeps me working with actual unclogged grit.

I'm curious about this Indasia Redline Rhynowet paper though... If you can clean out 600 and 800 grit, that's handy!

 

[Jon Rista]

The only scratches will be from that last grit. For me, that’s 2000.

Great post, thanks!

I am curious about the quoted bit. You sand to 2000! I've stopped at lower grits, because of all the proclamations that sanding to a higher grit limits finish penetration. I have read/heard that, but, I haven't tested it much. I've used oil based finishes on some things that I have sanded to 1200 or 1500 grit, and in teh case of pens even to 3000. It did kind of seem like the oil more sat on the surface, than penetrated it, but...it was highly anecdotal, and my ultimate goal was to get things done, than to verify the hearsay.

I guess for film finishes, penetration might not be an issue. For water based, they seem to mostly just sit on the surface anyway. I mostly do oil based finishes of some kind or another, or shellac (which also does penetrate a bit, not as much as oil), so I've wondered what grit can you really sand to, and still get all the benefits oils (or shellac) have as finishes.

 

[John K Jordan]

Sanding grits.
To me, the max grit used depends on the type of wood (e.g. ebony vs oak) and the type of finish. I have grits to 24000 (for restoring plastic aircraft windshields) but never use anything that high at the lathe. I did use up to 1500 recently as the last sanding stage on acrylic before polishing.

 

[Marc Banka]

Great post, thanks!

I am curious about the quoted bit. You sand to 2000! I've stopped at lower grits, because of all the proclamations that sanding to a higher grit limits finish penetration. I have read/heard that, but, I haven't tested it much. I've used oil based finishes on some things that I have sanded to 1200 or 1500 grit, and in teh case of pens even to 3000. It did kind of seem like the oil more sat on the surface, than penetrated it, but...it was highly anecdotal, and my ultimate goal was to get things done, than to verify the hearsay.

I guess for film finishes, penetration might not be an issue. For water based, they seem to mostly just sit on the surface anyway. I mostly do oil based finishes of some kind or another, or shellac (which also does penetrate a bit, not as much as oil), so I've wondered what grit can you really sand to, and still get all the benefits oils (or shellac) have as finishes.

If one were, let’s say painting the wood, or using any other film finish, the surface needs to have tooth. Some roughness on which to bind to. A very slick surface doesn’t work well. It has nothing to do with penetration, only adhesion.

I find that with good light, as described in my post, as I move to finer grits the amount of very fine detail in the grain becomes more noticeable. I start to see more tiny connective structures,,details. These things are visible at higher grits. Sanding to let’s say 320 will be smooth, and might be quite glossy, but the finest details won’t show. Then finish can’t reveal more than is revealed through surface quality.

When I’ve completely the sanding (2000),,the surface is quite glossy. Not from burnishing, but from making those scratches as tiny as possible. At that point finishing becomes very easy, unless you want a film finish. I use home made DO, shellac, oils and waxes-all work just fine. Plenty of finish penetrates, and establishing a nice soft sheen is as easy as wiping the excess and buffing with a soft cloth. The shine is built in and the finish merely seals it all.

My methods work for me. I hope this is of help to you or anyone else.

These are the best detail pictures I could find. Both pieces are Oak of some ilk. Sanded, but no finish. I wish I had blown the dust from the pores in the right hand piece.

.

 

[Tom Gall]

If one were, let’s say painting the wood, or using any other film finish, the surface needs to have tooth. Some roughness on which to bind to. A very slick surface doesn’t work well. It has nothing to do with penetration, only adhesion.

I find that with good light, as described in my post, as I move to finer grits the amount of very fine detail in the grain becomes more noticeable. I start to see more tiny connective structures,,details. These things are visible at higher grits. Sanding to let’s say 320 will be smooth, and might be quite glossy, but the finest details won’t show. Then finish can’t reveal more than is revealed through surface quality.

When I’ve completely the sanding (2000),,the surface is quite glossy. Not from burnishing, but from making those scratches as tiny as possible. At that point finishing becomes very easy, unless you want a film finish. I use home made DO, shellac, oils and waxes-all work just fine. Plenty of finish penetrates, and establishing a nice soft sheen is as easy as wiping the excess and buffing with a soft cloth. The shine is built in and the finish merely seals it all.

My methods work for me. I hope this is of help to you or anyone else.

These are the best detail pictures I could find. Both pieces are Oak of some ilk. Sanded, but no finish. I wish I had blown the dust from the pores in the right hand piece.

View attachment 76120.View attachment 76119

Totally agree, Marc. I don't turn much anymore but when I do I rarely turn utility pieces. For decades I've sanded up through the higher grits with paper, 3M pads, and ending with Abralon 2000 & 4000 grit pads. The wood kind of glows. I hand sand mostly - especially at the highest grits (very fine concentric scratches). Never had a problem with any finishes.
If I'm going to airbrush or paint with a brush I usually only sand through #220 or #400 - depending on the item and/or the wood.

 

[Jon Rista]

If one were, let’s say painting the wood, or using any other film finish, the surface needs to have tooth. Some roughness on which to bind to. A very slick surface doesn’t work well. It has nothing to do with penetration, only adhesion.

I find that with good light, as described in my post, as I move to finer grits the amount of very fine detail in the grain becomes more noticeable. I start to see more tiny connective structures,,details. These things are visible at higher grits. Sanding to let’s say 320 will be smooth, and might be quite glossy, but the finest details won’t show. Then finish can’t reveal more than is revealed through surface quality.

When I’ve completely the sanding (2000),,the surface is quite glossy. Not from burnishing, but from making those scratches as tiny as possible. At that point finishing becomes very easy, unless you want a film finish. I use home made DO, shellac, oils and waxes-all work just fine. Plenty of finish penetrates, and establishing a nice soft sheen is as easy as wiping the excess and buffing with a soft cloth. The shine is built in and the finish merely seals it all.

My methods work for me. I hope this is of help to you or anyone else.

These are the best detail pictures I could find. Both pieces are Oak of some ilk. Sanded, but no finish. I wish I had blown the dust from the pores in the right hand piece.

View attachment 76120.View attachment 76119

Thanks. Excellent example. I get that kind of sheen on my pens, as I often sand them (wood included) up to 3000 grit. I haven't tried sanding that far up the grits with larger items...but, I'll have to give it a try. The latest holly pieces, I still see some faint scratch marks, even though my final pass was with some of the gray 3M nonwoven abrasive pads, which are effectively are 1500 grit. I wonder if I can smooth things out a bit more...

 

[hughie]

I also think, I'm much pickier than the average turner, and I am demanding more of myself, than the average turner might demand of themselves? I've decided to simplify my sanding process a bit as a result, and not be too concerned about how things look right in the "middle" of the process, and be more concerned about how I start (that first grit, and truly getting rid of any tool marks, tearout, etc.) before continuing, and then spending the necessary time with the final grit (and maybe other things like fine 3M pads and the like) to really finesse the final result.

Well being fussy will get the results you're looking for Jon. I had to do something very similar in the beginning, it worked for me

 

[robo hippy]

This brings to mind "Chatoyance" which is a term that I think gets over used in turning and some woods. The term comes from the gem stone world, and refers to how light reflects/refracts off of the material as light moves across it. Now it gets applied a lot to wood. Some woods that come to mind are Koa and Bay Laurel/myrtle wood, and I have heard that true Cuban Mahogany will have this property. Most woods do not. but to bring out that "glow" you do need to sand to super fine grits, like 2000 and above. Not an easy thing to do, and not all woods are capable of getting there no matter how fine you sand.

robo hippy

 

[Jon Rista]

This brings to mind "Chatoyance" which is a term that I think gets over used in turning and some woods. The term comes from the gem stone world, and refers to how light reflects/refracts off of the material as light moves across it. Now it gets applied a lot to wood. Some woods that come to mind are Koa and Bay Laurel/myrtle wood, and I have heard that true Cuban Mahogany will have this property. Most woods do not. but to bring out that "glow" you do need to sand to super fine grits, like 2000 and above. Not an easy thing to do, and not all woods are capable of getting there no matter how fine you sand.

robo hippy

I am not sure I agree here. Chatoyance refers to the nature of how the Cats Eye gemstone reflects light. It specifically refers to how light shimmers off of linear facets of the stone just beneath the surface which produce a band or bands of reflected light.

Most species of wood will exhibit some chatoyance when finished with the right kind of finish. Some woods, particularly figure in woods, will be more chatoyant than others, but most woods will exhibit that kind of banded reflective behavior when finished with something that penetrates a little and allows the fibers not just on the surface but also below to reflect light in that manner. I have noticed this effect in most of the woods I finish, and it is the main reason why I prefer oil over film finishes and water based finishes.

I've also read other debates about this in the woodworking community. Some people believe it only applies to particular woods that are particularly chatoyant, while others consider it a more innate characteristic of the fibrous nature of wood, when those fibers reflect light at depth and produce that shimmering effect. I can't say that 100% of every piece of wood I've finished exhibits the effect, but I have seen that banded reflective nature in the majority of pieces I have finished across a wide range of woods. I don't think it is only a species-specific characteristic...I think it is more that certain species exhibit the effect more strongly than others, but a lot more than just a few woods can exhibit the effect.

The key is the fibers of the wood and saturating them with something that allows deeper penetration of light than just reflection and dispersion off the surface. Which is, pretty much, exactly why the cats eye gemstone exhibits this effect, from whence the term comes, as well...light penetrates into the "fibers" of the gemstone and reflects off of them at depth.

 

[robo hippy]

I would say that if the finish is making it appear "chatoyant" then the wood itself has no chatoyance.

robo hippy

 

[Jon Rista]

I would say that if the finish is making it appear "chatoyant" then the wood itself has no chatoyance.

robo hippy

Chatoyance refers to a characteristic of how the light is reflected and dispersed off the wood. Since it has to do with the nature of light reflecting off aligned fibers, technically speaking, most if not all woods can exhibit chatoyance under the right circumstances. There is a site from a project that has been testing the chatoyance of all woods. They created a scientific process to measure it and a standardized way of demonstrating it visually on the site. I'm drawing a blank right now, what the url is. When I find it I'll share it.

Woods with high figure, such as ripple figured maple, will exhibit chatoyance in the figure without a finish, because the figure tends to tighten the "beam" of chatoyancy. It becomes much narrower and more concentrated, thus brighter, and therefor easier to see. For many woods, the effect is much broader, and the "band" or "beam" of chatoyancy is wider. Where with a Cats Eye gem, the band is very small, maybe 1/8" or narrower, with wood it could be inches wide. With many woods that you don't easily see chatoyance without a finish, if you bring them under the right kind of light and rock the piece back and forth, you'll usually see something, if faint. The fibers are reflecting light the same way a Cats Eye gem or a literal cat's eye does.

It is not a matter of "does" and "does not" but instead a matter of degree. Just like the chatoyance in ripple figured maple can be greatly enhanced and become almost three dimensional with a good finish, a LOT of other woods can exhibit the same effects with a good finish. You need some penetration, because this is an effect that requires depth of reflection off of fibers, not just surface reflection. So any finish that does not penetrate, will not ENHANCE the chatoyance of any given wood, and in some cases may obscure or diminish it (high solids finishes, i.e. most water based.)

I'll see if I can remember the name of that site for the chatoyance project, which was done in a very scientific way. If I find it I'll link it, but...I strongly disagree with the notion that some woods "are" chatoyant while others "are not" as it just doesn't match the fundamental physics of why it occurs in the first place.

 

[Jon Rista]

Here we go:

PZC Chatometry – A standard system to measure wood chatoyance

They haven't measured all woods yet, but, as far as I know, all the woods they have tested, do exhibit chatoyance. They classify one of the attributes "scale" and there is definitely a difference in scale. While some woods may exhibit fine scale chatoyance and lots of it in figure or just the fibers of the wood, other woods exhibit it at a very broad scale, and while scientifically it is still chatoyance, its not what some wood workers would understand as chatoyance. The fundamental physical phenomena is the same, though, regardless of scale...the differences in the nature of wood fibers and how they transmit and reflect light affect the various attributes of the chatoyance they exhibit.

 

[robo hippy]

This makes me think of a bay laurel coffee table I made once. If you looked at it from one end, the 1/4 sections would be dark and light. If you looked at it from the other end, the dark and light reversed. If you looked at it from the side, it was pretty much all the same color. I will check out that article. Oh, I did see a set of folding screens, the privacy types, maybe in Fine Woodworking. The artist made them according to how light reflected off of them to make a pattern with it. Pretty stunning! I could never make some thing like that, I don't have that type of imagination.

Hmm, well, it seems that softer woods have a lower rating than harder or denser woods. No Koa on the list, or Cuban mahogany, or Bay Laurel. For sure, these woods will "glow" far more than most others. I guess I can see what they are measuring, but it didn't really clear things up for me. What I am still wondering was how fine were the surfaces sanded to, or were they hand planed which will leave a more shiny surface....

robo hippy

 

[Jon Rista]

This makes me think of a bay laurel coffee table I made once. If you looked at it from one end, the 1/4 sections would be dark and light. If you looked at it from the other end, the dark and light reversed. If you looked at it from the side, it was pretty much all the same color. I will check out that article. Oh, I did see a set of folding screens, the privacy types, maybe in Fine Woodworking. The artist made them according to how light reflected off of them to make a pattern with it. Pretty stunning! I could never make some thing like that, I don't have that type of imagination.

Hmm, well, it seems that softer woods have a lower rating than harder or denser woods. No Koa on the list, or Cuban mahogany, or Bay Laurel. For sure, these woods will "glow" far more than most others. I guess I can see what they are measuring, but it didn't really clear things up for me. What I am still wondering was how fine were the surfaces sanded to, or were they hand planed which will leave a more shiny surface....

robo hippy

I don't think there was any particular special processing of the woods. Basic planeing with a thickness planer was what I thought from my last exploration of their process. They have not tested all woods. I've been working on a project myself the last couple of months, a web app that will use AI to identify woods. In that process, I have had to explore a LOT of data on woods, find a LOT of images to train the AI. I've discovered there are over 500 types of wood, closer to 600 I guess... So, I don't think that this Chatometry project is even close to cataloging all woods. It'll take time.

The effect is the same in all woods, where the fibers reflect and disperse light a certain way. This creates that "band" of brighter reflectiveness. One of the key attributes that is different with every wood, is the scale. Highly chatoyant woods tend to have a smaller scale...the bright band of chatoyance is narrower with these woods, and more light is concentrated in it, so its more notable. Other woods have a much larger scale, the band of chatoyance is very broad. So the light is not as concentrated, and it may not even look like a band (i.e. in total scale, it could be feet wide rather than inches or less!) However the effect is the same, and it is chatoyance, and the study is demonstrating that most likely, all woods exhibit the effect, to one degree or another...meaning it is a matter of degree. So while some woods are HIGHLY chatoyant, like some of the ones you mentioned before, others are not, even though they still exhibit the effect.

I was turning some fairly bright white sycamore the last couple of days. Because of this conversation, I was wondering about it, as sycamore doesn't exhibit a lot of reflection, so I started taking a much closer look. As it turns out, it DOES exhibit chatoyance, but its different than other woods due to the nature of the fibers. There are the very fine whiter fibers, which do reflect light and you can see faint chatoyance...however there are other fibers, tan or browner in color, that are more scattered and widely separated in the wood. These fibers actually exhibit fairly strong chatoyance. The effect doesn't look the same as say highly figured maple, which for me is some of the most chatoyant wood I currently own, and because of the widely spaced fibers, the band of chatoyance is really huge (probably a foot wide or so, so on these smaller pieces that are just a few inches in size, much larger than the piece.) I can however, with just moderate direct light, clearly see the chatoyant reflections off of these tan/brown fibers throughout the wood grain, and it is a shimmer just like any other chatoyance. The wider spacing of the fibers makes it harder to see, but the effect is the same. Shellac or oil finish does improve the depth and appearance of the effect. It is a bit of a glow, but that glow exhibits a shimmering as the pieces are rotated around in the light. So I wouldn't say its JUST a glow...it is chatoyance.

I think the key is that, chatoyance is the result of light reflecting off of aligned fibers, not just on the surface but a little ways into the surface of the wood, and the physical characteristics of that reflection, where light may bounce off of one fiber and onto then off of another, etc. etc. that creates a band of reflection. It is also more than just reflection, at these scales diffraction plays a role as well, which is why the effect can occur even when some of the fibers are separated from each other, as in the case of the sycamore. The band scale can vary, but the fundamental physics of what's happening are the same.

 

[robo hippy]

Well, I am thinking that with sanding, you are leaving scratches, which will effect the reflection of light. With a hand plane, not a power plane, you are cutting the fibers off and you get a much cleaner surface. I think you would want to sharpen your plane irons on a high grit, like 16000 or more stone for the most "perfect" cuts. The difference is huge, but when sanding my bowls, I don't go beyond 400 grit.

robo hippy

 

[Jon Rista]

Well, I am thinking that with sanding, you are leaving scratches, which will effect the reflection of light. With a hand plane, not a power plane, you are cutting the fibers off and you get a much cleaner surface. I think you would want to sharpen your plane irons on a high grit, like 16000 or more stone for the most "perfect" cuts. The difference is huge, but when sanding my bowls, I don't go beyond 400 grit.

robo hippy

I disagree. Its not sanding. Sanding won't cause chatoyance. Its an intrinsic property of the natuer of fibrous materials that allow light to penetrate a ways.

I know some people insist that chatoyance only exists on some woods. Its really that chatoyance is an intrinsic property, but that some woods exhibit stronger chatoyance than others, especially when there is figure or other aspects to the wood that can tighten the range across which the beam of concentrated light occurs. In my experience, pretty much any wood that exhibits figure, will exhibit much higher chatoyance in the figured areas, than other areas. Cottonwood, of which I have more than I care to admit, isn't overtly chatoyant. It will exhibit that shimmer, but with a larger scale on even grain. However, in figured areas, cottonwood can be highly chatoyant.

In any case. I've...made my case, I'll just leave it at that. I think there is a fundamental science to this, an there is an organization testing every wood in existence to determine, according to the core properties they have observed, just how much chatoyance each type of wood exhibits. I think their results largely settle the question.

 

[robo hippy]

After pondering this for a day or so, I will say that surface prep will make a HUGE difference in light reflecting properties. You can't beat a hand planed surface for reflective properties. Sanding up into the auto/metal polishing grits also leaves a very glossy surface, as do the types of finish applied. I guess you could compare a hand sawn surface for emphasis. Yes, the wood plays a part, but surface prep is another part.

robo hippy

 

[Jon Rista]

After pondering this for a day or so, I will say that surface prep will make a HUGE difference in light reflecting properties. You can't beat a hand planed surface for reflective properties. Sanding up into the auto/metal polishing grits also leaves a very glossy surface, as do the types of finish applied. I guess you could compare a hand sawn surface for emphasis. Yes, the wood plays a part, but surface prep is another part.

robo hippy

So, yes...nature of the wood surface is a factor in the EXHBITION of the effect of chatoyance. FWIW, I would not say it CAUSES it, it affects how the effect exhibits.

The nature of the surface of the wood will affect how the surface interacts with the wavefront of light. A rough sawn surface that leaves lots of ridges and valleys, torn fibers, etc. will scatter a lot of light, which is partly why dry woods look flatter and often brighter than finished woods. Finishing, technically, I wouldn't say "darkens" with finish (although there are exceptions do that, where chemistry plays a role), but it is more that a finished surface changes the nature of how the surface interacts with the wavefront. An unfinished surface will scatter more light. A film finish that sits on top of the wood will affect how light is initially presented, and affect scattering to a degree. A penetrating finish will have a more significant impact as it helps light not only interact with the surface but also penetrate the surface and interact with the fibers differently.

There are several factors of how the wavefront interacts that affect how the wood looks: reflection, refraction, and even diffraction. Some light will reflect, some light will refract, and some light will diffract among the fibers at a more microscopic level. There are also differences in exactly how these affect the wavefront. Reflection off of a rough surface will result in a lot of scattering, whereas reflection off of a super smooth well planed surface will scatter less. Both are reflecting, it is the nature of how light is reflected that changes. Refraction will occur with any wood surface, to differing degrees. Some light will refract (be bent into the wood by its material and fibers). A smooth surface will present a more consistent surface and refraction will be more consistent. A penetrating finish will help light refract into the wood more than no finish or a film finish. Diffraction is an effect of how a wavefront interacts with small to microscopic obstructions, and the fibers themselves can present an obstruction that light will diffract around, creating other kinds of effects that reflection and refraction cannot.

Chatoyance will exhibit most powerfully when the surface is very smooth, with a good penetrating finish. So yes, a hand planed surface will likely present the best possible wood surface, and even without a finish, will improve chatoyance. A good penetrating finish with that planed surface will allow for better penetration of the wavefront and chatoyance will maximally exhibit. A sanded surface with a good finish will be pretty close. A finish plays a role here in how light reflects and refracts, and since chatoyance is dependent on the fibrous nature IN DEPTH, deeper penetration will allow more fibers, not just those near the surface but also slightly deeper, to affect the way chatoyance presents.

So I agree, surface prep and finish both play a role in how this INTRINSIC property of, IMO, all wood, exhibits in the end. Unprepared or unworked wood will scatter the most light most of the time, which will obscure the effect of chatoyance (you can sometimes still see it, in the right kind of light, even with rough unworked woods, but the scattering limits how much light can penetrate and interact properly with the fibers of the wood to cause the effect). A very cleanly finished surface, say in the case of turned items maybe scrapers are the best way to produce the best possible surface, with high grit sanding being second, will certainly help. How you finish will as well, and surface film finishes that don't penetrate, in my experience, do not do nearly as much to help the wood exhibit its chatoyance as much as anything that does penetrate. Even a little penetration helps...which is why I think shellac can improve chatoyance. While it mostly forms a film, some of it does penetrate a little, and when sanded back presents a very smooth surface as well. For the best exhibition of chatoyance, though, penetrating finishes, which I think are mostly oil based finishes (not sure if there are any others, perhaps CA if its thin enough and allowed to actually penetrate for a while before hardening), are the best way to allow the light to reach beyond the surface of the wood, interact with those fibers (which does also involve diffraction as well as refraction and reflection) and produce the maximal effect.

 

[Steve Tiedman]

As I went through the gallery of the AAW symposium today, I took a close, critical look (but no touching!) at many of the simple turnings such as bowls, platters, and similar. A few that I saw had surfaces that were simply flawless, not an abrasion mark to be found. But I saw many pieces where if I had my eye within inches of the surface, and if I studied it closely, I could see sanding marks. Most were incredibly fine, a few were pretty obvious, and some rather glaring in how the surface film finish sheen was affected by the sanding.

Those that I said were incredibly fine scratches, I think those turners probably did everything they could to approach a perfect surface. And you know something, once I pulled my eye farther away than 10-12 inches, the surface and the finish was perfect. Beautiful. Made by human effort and skill, and with the love of their craft.

For all of us who may drive ourselves crazy in an endless pursuit of perfection, let's give ourselves a break and not foresake our very best effort chasing after what we feel is perfection.

 

[Jon Rista]

As I went through the gallery of the AAW symposium today, I took a close, critical look (but no touching!) at many of the simple turnings such as bowls, platters, and similar. A few that I saw had surfaces that were simply flawless, not an abrasion mark to be found. But I saw many pieces where if I had my eye within inches of the surface, and if I studied it closely, I could see sanding marks. Most were incredibly fine, a few were pretty obvious, and some rather glaring in how the surface film finish sheen was affected by the sanding.

Those that I said were incredibly fine scratches, I think those turners probably did everything they could to approach a perfect surface. And you know something, once I pulled my eye farther away than 10-12 inches, the surface and the finish was perfect. Beautiful. Made by human effort and skill, and with the love of their craft.

For all of us who may drive ourselves crazy in an endless pursuit of perfection, let's give ourselves a break and not foresake our very best effort chasing after what we feel is perfection.

Thanks for taking the time to do that, Steve. I agree with your conclusion too. I have given myself more leeway since this thread.

I guess I am not surprised by the results, or the range of results, you were seeing. The holly pieces I was working on (temporarily tabled that project to make some items requested by customers), are quite good, I think. They do have some fine scratches, and the finish (which I have left matte, I did not polish it to a shine like I usually do) did make some of the scratches more visible...but, as you mentioned, at normal viewing distances they cant' be seen. It requires close scrutiny, and since the finish IS matte, that helps obscure them. It takes rather direct lighting at the right angles for anything to be seen.

Since I started this thread, I've come to accept that as acceptable quality. I also started at a worse position than I ended up. I was getting even worse scratches when I started this thread than when it concluded before, that usually showed up once I put on the finish and polished it, which I am pretty sure were from coarser grits. I was also generally stopping at 400 or 600, even if I temporarily sanded up to 800 or 1200 (or beyond) as I would back up the grits again to try and make sure I wasn't closing off pores. I gained sanding skill with this thread, and have acknowledged that perfection, or even being appreciably close, is not necessarily an attainable goal, or at least...not with every piece and every finish (I still have to try Danish/Tung oil finishes and wet sanding with the oils.) I also have learned I can probably sand up to higher grits when using shellac as a base finish (topped off with a wax finish for protection.) On the final holly pieces, I'll be sanding to 1200 and maybe 1500 to see how things go.

Something else I learned is that, you can actually move through the sanding process fairly quickly...or at least, a LOT quicker than I used to deal with. The first grit, and the last grit or couple grits, are the most important. I used to sand both directions, and even sand both directions with each and every grit, which often greatly extended the effort, and often did not produce the best results. What I do now is sand with the lathe on, spending a bit more time on the first grit, and progressing to the last or next to last grit. I sand with each grit, until I can no longer find any notable scratches from the prior, and its all with the lathe on now, until those last grit or two. Then for the last grit or two, I'll start lathe on, just to get through the prior grit's scratches, then go lathe off and hand sand until I'm satisfied. That can take a little while, and I'm picky so it probably takes me longer than most...but in the long run, this newer approach (for me) is a lot faster than what I used to do. Further, with careful lighting and use of light to find any problem scratch areas, I'm able to clean up everything with the final grits (which are often now 800, 1200, or maybe even 1500) leaving a very nice, fine, and apparently scratch-free finish in the end. I mean, there are scratches, but I'm getting quite good at hiding them in the grain or wood features now. Once hidden, their existence really matters not.

I'm still primarily working with a shellac based finishing process, though, and I think whoever said it earlier in the thread was correct: Shellac really does seem to enhance defects and make it harder to correct them. I have noticed the same with poly (primarily Minwax WOP) and spar as well...they really enhance defects. I am really looking forward to working with danish oil and some of the processes some turners have outlined here (and in other threads). I think, with wet sanding with danish oil, I'll be able to achieve a surface and final finish that meets my picky perfectionist expectations. I have a bunch of bowls and platters to turn and try things on over the next couple months.

 

[robo hippy]

Supposedly, abrasive grit scratches in wood are invisible to the human eye at around 700 or so grit. Can't remember where I heard that, but it seems to be correct, though I have never seen 700 grit.... For my daily use bowls, I stop at 400, and use the grey synthetic steel wool pads. I can't see scratches after I am done. Metal is another thing though, grit scratches up to 8000+.

robo hippy

 

[John K Jordan]

Metal is another thing though, grit scratches up to 8000+.

For metals I often follow sanding with Liberon 0000 steel wool then if I want a high polish use cotton cloth with Simichrome or any other kind of polishing compound. Reflects like a mirror.

Amazon.com

Cheaper now than when I bought it maybe 8 years ago.

A roll of 0000 like this will last for decades. I'll leave what's left to someone in my will.

 

[Steve Tiedman]

Boy, if I wasn't still working on the last 1/3 of a roll I bought at least 20 years ago, I'd order that roll now.

What I use steel wool the most for (#0000) nowadays is to clean my bandsaw tires after a session. I spin the wheels by hand, and just hold the wool with moderate pressure against the tire. After a couple-three revolutions, it's clean. Then a thorough shop vac cleaning of everything.

 

[Jon Rista]

I have a small roll of #0000 steel wool that I've had for a few years. I pinched off small little bits in the past to clean up scratch marks. I only use it occasionally now, as unless you have the wood pretty thoroughly sealed, I found that fibers and dust from the steel would often get embedded in the surface. Sometimes even with a finish. So I haven't used it as much these days.

I do use these Mirka Mirlon nonwoven pads, ranging from 360 grit (maroon), to gray (1500 grit), to brown (2500 grit). They seem to work a bit better, as they don't leave any fibers like raw steel wool, although they do leave dust. I usually use them as a final pass on shellac-sealed surfaces to clean up any notable scratch marks. It seems the dust they leave behind blows off easily once the wood surface is sealed, and I've never had any fibers get stuck in any grain like with the steel wool (which can still happen with a seal coat, if the grain is open or anything like that.)

I haven't tried using the steel wool to clean my bandsaw tires. I have plenty of steel wool, and the only use its had lately is cleaning up burrs and corners on machine parts and chucks and the like. Should start cleaning my bandsaw wheels with it.

 

[John K Jordan]

What I use steel wool the most for ... is to clean my bandsaw tires after a session

Yikes, what's this cleaning bandsaw tires about? I haven't cleaned tires on my bandsaw tires since, well... never.
I cut a lot of both green and dry wood, 1/2" 3TPI Lenox blades.

Do you get some kind of buildup on the tires? From cutting what?
Have never seen that here, with two shop bandsaws and a Woodmizer.

I do sometimes get buildup on the inside of blades when processing certain green woods, but that's easily removed in a few seconds with a simple little tool I made.

JKJ

 

[Steve Tiedman]

Well, there is nothing modern about the otherwise good condition tires, the original rubber is on both 1980s gen Delta 14" saw. They aren't sticky, nor dry rotted or rock hard, but sawdust does grab onto these tires. Wet dust seems worse than dry, softwood dust worse than hardwood. Blade tension is released after each session. But the tires are in great shape, no reason the replace them. I'm guessing, then, that newer style polyurethane tires don't collect dust as much. Often times I can clean the tires just rubbing them with my fingertips. This shows the 4:00 position of the upper wheel, a wee bit of dust left over from the last cut followed by a finger swipe.



I just ripped a 36" long strip of dry, 1" thick red oak. Below is typical of what gets left on the black tires, more on the bottom tire. One quick finger swipe an inch or so long shows the clean patch. If the dust is stuck on, then I use the #0000 steel wool on it. John, maybe that big dog dust system you have on your saw keeps things cleaner than the mediocre dust collection by way of a shop vac these saws have.