turning "dry" bowls in summer humidity

[Peter Skellenger]

I have a lot of rough turned bowls that are really screaming to be turned but I am a little hesitant to finish them in the summer. I am talking about bowls that are between 3/4" and 1.5" thick, anchorseal on end grain and sometimes the whole bowl. The were roughed green, sealed, and left in the shop for a month or 2 during winter (cooler than the in floor heat of the house) and then brought inside to very low humidity and 70+ degrees. This inside environment gets rather cool and humid in the summer and i can actually see movement in bowls roughed over a year ago. I live in the Upper Peninsula of Mi. It is hot (90+) and humid(80+%) right now and has been for a good portion of the summer (yes, summer is a season in the UP of Mi!) . I do not have a moisture meter or accurate scale. The last week or 2, I have been microwaving the year old bowls for 2 min cycles (maybe 10 times) and allowing to fully cool in between. I then simply finish them. Pretty non-scientific and potentially stupid, I know! I have had pretty good success with a cpl exceptions (american elm moved a bit and also Eastern Hophornbeam or "ironwood"). I have some really nice ones I would like to finish but don't really want to experiment on them. Any suggestions for summer bowl finishing?

 

[DeanGThomas]

Not trying to do anything other than ask the question here:

Why not spring for the few $$ and purchase a decent scale or a half-hearted moisture meter? You seem to be getting serious about your bowls, maybe just one more serious tool will help you a lot.

 

[John Nicholas]

Drying Bowls

Nothing beats trying to turn one.

One year since roughed. Rule of thumb, wood drys at 1 inch per year. You have also given it a microwave boost.

Try finish turning one now. If you get it finished and it doesn't move or warp, great. If it does, it may work the way you intended or it may work another way.

Then you know.

Let us know how it goes.

John

 

[Richard Baker]

Peter,
You didn't say what the temp. & humidity were in the shop during winter. But in any event I like Dean's suggestion and am considering it myself. If you are seeing stuff move a year after being rough turned, it may be gaining moisture. The post office (whowouldathunkit?) offers a couple of fairly modestly priced electronic scales that might be helpful. Have forgotten their weight ranges, but might be too small for your work. Was considering the larger size when several things happened that put my wood turning efforts mostly on hold for a while.

Spent a year in Saginaw the summer of '64, and it was fairly warm then, but temp. never even got to 100.

Has anybody out there tried the postal scales?

 

[Barry Elder]

Weight 'n Weather

Hi Peter,
I bought a postal scale on the erstwhile "auction" channel and it certainly will give you accurate measurements for weight loss and gain. If you really want to study how the weather up there affects the different types of wood, you could get some graph paper and keep a record over time to see what if any effect the seasons have.

Barry

 

[Peter Skellenger]

yeah, I will eventually end up getting the moisture meter or scale.... BUT, the meter leaves holes in the bowl and I doubt everyone turning bowls uses a meter on all of them. Pinless will not work on bowls. The scale means I have to do all sorts of weighing and keeping track of stuff. I am talking about hundreds of bowls here, not just a few. It seems to me the best bet is to turn em in the spring and fall! That's a joke but seems slightly logical but not practical. I thought i could get a pin meter and take a reading near the rim which is warped anyway and will be turned off or on the tenon which i remove in the end anyway. I guess I question whether anyone else is doing this. I am def pretty serious with the bowls.... a small kiln is prob the way to go...

I did try it. I mentioned the elm and ironwood... the elm moved the most and was extremely warped to begin with. I am not talking about a lot of movement here either... but I notice it, especially sanding. I know the rule of 1 inch per year but I do not agree with that at all. I guess it is a good "rule of thumb" but it is flawed in the sense that all wood is not equal. I have read the book "Understanding Wood" by R. Bruce Hoadley and he discusses this in there. Wood drying is dynamic and very much depends on the species and most importantly, the environment or location it is in. For example, drying 1" White Pine boards right next to a pile of 1" Black Walnut boards will yield radically different drying times. Assume this is done Michigan. Take the exact same piles and drop them in Arizona. I am pretty sure the drying time of both will be shorter in AZ than MI but will stay fairly constant relative to each other. The amount of sap wood vs heart wood also plays a large role in dry time as well. This is evident in a cherry or walnut board or bowl that contains sap wood. I am by no means an expert on this obviously, so don't take anything I am saying as gospel!! This is what I have taken from what I have read and/or applied (however I do know for sure pine will dry faster that walnut). Interesting stuff to me! I guess the point of my post was more to see what anyone else is doing to finish bowls in the summer. I am using the microwave as a little insurance I guess but with no actual knowledge of what I am doing! I def know that the bowls are taking on water in the summer and will def lose it in the winter. THAT is given. The question is what are others doing, if anything, to finish bowls in the humidity of summer.

 

[DeanGThomas]

Did a Google search.[What did we do without Internet access??]

www.balances.com/home.html shows a bunch of scales at regular and sale prices. Ranges are between 4 grams (waste of space except for microturners in our case) up to about 7000 grams or 15 pounds. That would probably work for all but your largest, wettest bowls and it would work on those once they'd dried for a couple of months. Especially look under the "Under $50" category.

Again, the commonly held rule of thumb is a year per inch. That's for most domestic woods. I'd bet that exotics are a different deal. Rules of thumb are generalities that work for most COMMON situations.

 

[Peter Skellenger]

"temp never even got to 100" ... as if 100 is not hot??! If it's in the 90's, it is hot for me. I guess the humidity is the killer here. makes it feel much hotter

Yeah, the scale is prob a good buy. I guess I could at least use it for a while and keep track of species data and not every single bowl. That would seem to make a lot of sense actually! The bowls only spend a cpl months in the shop in the winter but the temp is around 67 avg and the humidity is not controlled at all... but with the in-floor heat and cold temps, I would imagine quite low!

 

[DennisM]

How long to dry

Here's a link to an article from the Iowa Department of Agriculture that rates the months of the year for their “effective air-drying daysâ€Â. This research was conducted for the upper Midwest. The concept is that each month of the year has a different drying capacity.

http://www.forestry.iastate.edu/publications/pubs-pdf/F-303.pdf

This piece is more specific that the old rule of thumb of an inch per year.

As a practical matter, I weigh each piece on a produce scale and the the piece is "dry" when the weight stops changing. The greatest variable seems to be the thickness. The 3/4 inch bowl blanks are ready to finish turn in 3 months. Thick pieces are closer to the year per inch rule of thumb.

Hope the article helps.

Dennis Belcher

 

[Richard Baker]

Yeah, the 90's is hot for me too these days.

 

[Peter Skellenger]

Cool. Thanks Dennis and everyone else! Looks like a scale will be a good investment. So many variables to consider when drying wood. I guess it would be kind of boring if every single piece of wood "turned out" the same. Thanks again. I can see I have been missing out by not signing up for the forum earlier! Good stuff!

 

[john lucas]

I don't turn a huge number of bowls but here in Tennessee a rough turned bowl will dry in 6 months or less without me doing a thing. Summer or winter doesn't seem to matter. I just weigh them periodically on a my bathroom scales. I put a 50lb anvil on the scales because I don't trust them for really light weight. I set the bowl on the anvil and then write the weight and date on the edge.
If you rough turn a fair amount you will always have more bowls dry than you can turn. I tend to rough out some and turn a few natural edge pieces that I turn green.This gives me the instant gratification while the others are on the shelf drying.

 

[MichaelMouse]

Gets pretty dry during heating season. 5% or less in my place. With wood only able to pull against itself, cutting thinner will give you a difference of 1% in dimension or so across the 7% difference in seasons. Hardly enough to worry about.

 

[Gretch Flo]

yeah, I will eventually end up getting the moisture meter or scale.... BUT, the meter leaves holes in the bowl and I doubt everyone turning bowls uses a meter on all of them. Pinless will not work on bowls.
Peter-I received a pinless moisture meter a few years ago as a gift and use it all the time. I think it said accurate to 1 ", but I think pending the types of wood it would still work in even thicker pieces (I'll try it when I get home). It is really neat to see the various moistures in a green turned small bowl-(which I do alot of). It doesn';t measure above 20%. A quarter inch bowl may take 4-5 days pending type of wood and you can follow them daily if desired. You can see where crotch figure. or heartwood vs sapwood will measure higher than adjacent wood. The base always measures more since mine are thicker. than the sides. It will even measure higher than true when your finger is under the inspected area!!!! Took me a few seconds to catch onto that!!!! . I believe mine is a Wagner and sold for $134 a couple of years ago. Last I saw it was $144 from Craft supplies, but haven't looked recently. Gretch

 

[Hugh]

Scale - My wife purchased a nice scale at a cooking store. It weighs in either onces or grams - up to 11 pounds. She did not use it much and I "borrowed" it and it now lives out in the shop - except when I make bread (I use the scale to weigh ingredents). I think the scale cost about $40. All electronic. Very handy tool.

I have found that if you are only weighing a few bowls - when they get near dry - I use an index card to keep track of the weights. If you are doing a bunch of bowls - I have found that writing right on the bowl is easier to keep track of the weights. One just has to sand them off or cut them away when re-turning the bowl.
Hugh