"Banding" on Hollow Forms

[Randy Anderson]

A few times I've had what I call "banding" show up on hollow forms right at the transition of the curve from bottom to top. It doesn't show up in my mineral spirits wipe and isn't due to scratches to tool marks. It jumps out when I put on oil. It's rare and I pay close attention to sanding up to that part of the curve from top and bottom as well as the transition. I try to make sure the surface is consistent re sanding direction and pressure up to and around the bend. I suspect it's due to the change from mostly pure side grain on that "band" to side and end grain as it curves away. On dark spalted wood it can be very noticeable as you can see. My remedy is to put it back on the lathe and, as messy as it is, go back to 80 or 120 grit and work the area up and down until I get a better blend. I was able to greatly reduce the banding on this piece but wondering if anyone with more experience has a trick for catching it before I apply oil. Water instead of MS maybe?

I know it's not terrible to the average observer but it's one of those things that jumps out at me and becomes all I see when I look at it.

 

[Brian Gustin]

wonder what would happen if you tried a water wipe instead of mineral spirits, if you refer to what I think I am seeing, I'd suspect the oil is raising the grain a bit - if you raise grain first with some water after final sanding, then re-sand at same grit, I wonder if that might help anything? Other than that it looks like a nice piece to me (other than that one bumpy spot near the top? maybe it's intentional, but to me it breaks up the flow of the form...)

 

[odie]

Randy, if it's what I think you mean, it's a natural part of the grain.

If not that, I've seen 600gt sanding scratches that are invisible to the eye, and as soon as I apply Danish oil, they are apparent. Usually this is more evident on the long grain, rather than the end grain...

-----odie-----

 

[Randy Anderson]

Thanks Odie. I suspect it is a "natural" effect of the grain. The tops on vases, mostly end grain, often look a shade darker than the rest of the piece due to how much oil they soak up. That's expected. I do a final end to end hand sand with 400 or 600, depending on the piece, to at least get and residual scratches running top to bottom and less noticeable. On a piece like this scratches at that grit if any won't show. I know your pieces are high sheen and gloss so ANY scratch jumps out I'm sure.

Brian, the "bumpy" top is on purpose. Trying different shapes and styles for vases and kinda like this shape for tops. Some more subtle than others. Got it from some ceramic ones around the house. Will see if a water wipe will show it or help. Like I said, it's rare but darn, at that stage it's a real pain to back up and fix.

 

[john lucas]

Sounds to me like possibly a burnish mark from your gouge heel. The crushed fibers will appear to sand out but the finish wont penetrate that area the same way and leaves a lighter ring. Rounding over the sharp edge of the heel will stop that.

 

[Randy Anderson]

John, I considered that and not ruling it out. I do keep the heels ground down on my gouges and even then I have to watch for them on the inside curves of smaller bowls. From watching a number of Richard Raffan videos these days I'm making a lot more use of my spindle gouge where I keep the heel well ground. This was punky spalted maple so would have been easy to get a burnish ring.

 

[Clifton C]

it's due to the change from mostly pure side grain on that "band" to side and end grain as it curves away

I believe you are correct, the oil is absorbed less in the long grain area. For me I see it more on softer woods when using a penetrating finish. I read an article on applying dye to ornaments and trying to minimize the light colored band at the equator. While long grain to end grain transition is extreme in a "squashed" sphere, I think it applies here as well. The fix for the ornaments was a wash coat of sealer (shellac?), then applying the dye with an air brush. The dye stuff does not apply here but maybe the seal coat is an option. An interesting experiment would be turning a long, medium and quick curve, applying oil and seeing how/if the width of the band changed in relation to the curve. Then the question would be, would a seal coat work, how thin to thin, and, how to apply evenly to what is essentially a sponge...

 

[Doug Freeman]

Agree that its due to the grain change. Is your pic just after application or is the oil cured? How long due you keep the surface wet before wiping the oil off? Have you tried more coats of oil and did it help? What is your final sanding grit?

 

[John Jordan]

A few times I've had what I call "banding" show up on hollow forms right at the transition of the curve from bottom to top. It doesn't show up in my mineral spirits wipe and isn't due to scratches to tool marks. It jumps out when I put on oil. It's rare and I pay close attention to sanding up to that part of the curve from top and bottom as well as the transition. I try to make sure the surface is consistent re sanding direction and pressure up to and around the bend. I suspect it's due to the change from mostly pure side grain on that "band" to side and end grain as it curves away. On dark spalted wood it can be very noticeable as you can see. My remedy is to put it back on the lathe and, as messy as it is, go back to 80 or 120 grit and work the area up and down until I get a better blend. I was able to greatly reduce the banding on this piece but wondering if anyone with more experience has a trick for catching it before I apply oil. Water instead of MS maybe?

I know it's not terrible to the average observer but it's one of those things that jumps out at me and becomes all I see when I look at it.

That's the only area of true "flat" grain there is. The rest has some degree of end grain and reflects the light differently. Some wood it's more noticeable than others. Walnut really shows this effect. Your piece is turned end-grain, if you turned a similar piece side-grain, the band would be vertical on two sides. Nothing will change it or "fix" it.

John

 

[Timothy White]

Those marks look like stress marks in the log. Stress marks (or lines) usually appear on the compression side of the tree due to either the tree leaning or from wind. Tool marks can be cut out as they are only superficial. Stress marks Can appear nearly half way to the center of the tree the tension side of the tree should not contain stress marks.
Bradford Pear seems to be one of the worst For stress marks.

 

[Randy Anderson]

I was able to rework and blend a bit more and now (pic attached) it's more of what I would expect. A messy task to re-sand once oiled.

 

[Richard Coers]

I consider that banding to be the only place you have true long grain like the flat face of a board. The rest of the vessel is some bit of longer pores heading towards end grain. Happens a lot when I dye the form.

 

[Mark Mandell]

Randy, I could be wrong, but from the photo it looks like your tuning is oriented "end grain" such that the banding you're seeing is the successive "edges" of the annular rings. You have on the top surface as well as on the bottom as you transition to the center of the piece?

 

[Randy Anderson]

Mark, yes it's an end grain piece. Spalted Maple, was fairly punky. The banding from the grain lines, especially on the top and bottom, is normal and the desired look. I'm used to paying attention to non grain line banding issues on hollow forms from tool or compression marks and do a lot of wipe downs looking for them. A perfect circle is so easy to spot around a vase and drives me crazy. I believe here it was the combination of the side grain oil absorption plus a bit of a compression mark right on the side grain area on soft punky wood that got me.

 

[robo hippy]

Could have been a bunch of reasons why that band showed up. I would guess part of it may have been because you were in a flat grain area, where you couldn't cut up hill or down hill no matter which direction you were going with your tools. Just another reason why I don't like punky wood..... Maybe stabilizing it before you finish turned and sanded might have helped. A penetrating oil finish can help stabilize the wood/grain.

robo hippy

 

[Larry Mercier]

I like Robo's solution but question whether wood stabilizer can be put on after oil has already been applied.

 

[Leroy Cook]

I was able to rework and blend a bit more and now (pic attached) it's more of what I would expect. A messy task to re-sand once oiled.

Since you were able to sand most of it out, would that support the conclusion that this was more of a compression mark?

 

[Randy Anderson]

Leroy, I think it was a combination of a compression line I missed or didn't show with my MS wipe and a little more sanding was needed.