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polymer and wood

Gary Chapman

Gary Chapman

Joined
Mar 3, 2009
Messages
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Location
Madison, Indiana
I have a customer who wants me to make a yarn bowl and imbed polymer clay designs into the bowl The clay must be cured in the oven to 250 degrees. Is this possible before it would catch fire?
 
Only one way to find out! 🙄

Do an experiment with a test piece using scrap.

Even if it doesn't catch fire, I suspect it won't be good for the bowl.......

Is it possible to cure the polymer clay pieces, and then insert them into the bowl?

ko
 
When I go camping, it seems like the wood doesn't want to catch fire at any temperature.🙄

I hear that some people up north cook a salmon on a cedar plank. I don't know how the plank fares, but I would guess that it out gasses some of the resins and other carcinogens that give the fish a good flavor. 😀. I just open the can and put the salmon on my sandwich.

I suppose that the best answer would be to put a scrap piece in the oven and make a trial run. I seriously doubt that it will catch fire, but it might turn darker and possibly warp. I won't mention any names, but based on a recent incident involving baking frozen french fries in the oven the wood might begin to char and turn black with a lot of smoking.
 
Walt wager is doing a demo at the Florida symposium in a couple of weeks.
He will be turning polymer clay.

Inlaying the cured clay in wood will probably work better than curing the clay in place within the wood.

250 degrees may not hurt the wood it is a function of time for how long the temperature is that high. Long enough it may ignite or char.
Is the ignition time for the wood less than the curing time for the clay?

I have done some pewter casting directly in it wood.
The molten pewter is at about 500 degrees and it does not scorch the wood however it cools rapidly.

Curing the polymer clay in the the wood you need to consider
the wood has to come to the curing temperature before the curing will start
Curing time after that depends in the thickness of the clay
Baking a 250 should not burn the wood but it will dry it more.
Does the clay change dimension when curing.

Putting the clay In place using epoxies or casting resins is worth considering.
Then you should be able to turn the whole surface

Al
 
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There was a great article by Jim Rinde I believe in Woodturning out of England on heating wood to near charring temperatures. It totally changes the color and handling of the wood. I don't get that magazine so can't look the article up. If I remember correctly his temps were closer to 350 or 400. I would simply stick a piece in the oven and see. 250 will probably change it some but not sure.
 
Here is some useful information that I came across while searching for something unrelated:

​

  • Ignition of wood takes place when wood is subject to sufficient heat and inatmospheres that have sufficient oxygen. Ignition can be of two types: piloted orunpiloted. Piloted ignition occurs in the presence of an ignition source (such as aspark or flame). Unpiloted ignition is ignition that occurs where no pilot source isavailable. The surface temperature of wood materials has been measuredsomewhere between 300 C and 400 C (572 F to 752 F) prior to piloted ignition.Unpiloted ignition depends on special circumstances that result in different ranges of ignition temperatures. At this time, it is not possible to give specificignition data that apply to a broad range of cases. With convection heating ofwood, unpiloted ignition has been reported as low as 270 C (518 F) and as highas 470 C (878 F).
    Source: Wood Handbook Wood as an Engineering Material,1999, Forest Products Laboratory, U.S. Department of Agriculture, Madison, WI.

The Wood Handbook is a very useful resource and is available to download for free on the USDA Forest Products Laboratory web site. The most recent revision done in 2010 is a major rewrite and is well w.orth downloading ... all 509 pages although you can download specific chapters if you wish.
 
Gary, there is a wealth of info on the Web. Life is short. You don't have to do experiments that other have already done. Besides, if your wood catches fire in the oven, your smoke detector is going to go off and your wife is not going to like the smell in the kitchen if she is like mine.

I presume your 250 degrees is Fahrenheit. Even at 250 Celsius it would not ignite. As Bill found on the Web (and I confirmed at a different site), it has to go well above 500 F before wood will ignite. However, 250 will probably dry your wood excessively, risking cracking if nothing else. Does your customer specify polymer clay? Does he/she know about other polymers woodworkers/woodturners use regularly that do not require heat curing but are just as pretty and you can create your own colors by adding colorants before casting? Polymer clay is PVC (according to Wikipedia) which is not fun to turn. (The shavings will wrap around anything that's rotating.) I would say Alumilite is something you would like to check out (see https://www.youtube.com/watch?v=9IErQYSQJT4). Alumilite turns well as you'll see in the video.

Have fun!
 
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I would imagine the polymer clay has some shrinkage in the curing process. Can't imagine it will stay in the wood, and remain the same size. The wood will have to be bone dry to have a chance. The pen turners use Alumilite and cast it to wood. It shrinks less tha polyester resin and sticks to the wood better.
 
Richard Coers said:
I would imagine the polymer clay has some shrinkage in the curing process. Can't imagine it will stay in the wood, and remain the same size. The wood will have to be bone dry to have a chance. The pen turners use Alumilite and cast it to wood. It shrinks less tha polyester resin and sticks to the wood better.
Click to expand...

I read somewhere polymer clay shrinks 1% or less.
If you are an optimist the shrinking wood will tighten the grip

Alumilite is great stuff but a totally different animal it is a liquid requires molds to hold it in place and some type of bubble control.
It cures similar to expoxy

The polymer clay has a claylike body and holds its shape similar to ceramic clays while it is cured.
 
hockenbery said:
I read somewhere polymer clay shrinks 1% or less.
If you are an optimist the shrinking wood will tighten the grip

Alumilite is great stuff but a totally different animal it is a liquid requires molds to hold it in place and some type of bubble control.
It cures similar to expoxy

The polymer clay has a claylike body and holds its shape similar to ceramic clays while it is cured.
Click to expand...

Since we have no idea what the design is, including size, 1% may not be a big deal. Since wood shrinks a lot less in one direction, that tightening will only be in one direction, and it will gap on the other direction. He said it would be imbedded in the wood, so there would not be a need for a mold. In reality, I guess all he wanted to know is when does wood burn.
 
I do have some experience using polymer clay inlays in woodturned platters.

1. You can bake the whole piece in the oven at those temps and you will theoretically be fine. I have done two myself and they both came out of the oven intact with no signs of charring. However, I was also using kiln-dried wood that had been sitting in my workshop for months beforehand. The risk is not the polymer clay curing temps charring the wood (way lower than the charring temp of wood), but that any residual water in the wood will boil (water boils at 212) and this could cause warping or cracking. On subsequent pieces, I used an industrial heat gun to cure, just to be safe. I mounted the heat gun (DeWalt D26950) on its side on a platform on my banjo using the spreader head on it, moved it to within about 1 cm of the inlay while the piece spun at my lathe's slowest speed (about 50rpm) and, with the gun turned almost all the way up, it was maintaining a surface temp of about 265 or so. I confirmed with an infrared thermometer. Done this method a couple of times, it works. However, if your lathe minimum speed is much more than this, this method won't work for you. You can always cure by hand with a heatgun, moving it back and forth, but it will take awhile. Or, you could get a motorized lazy susan/rotating display stand and hook something up like that. The slower the rotation, the better.

2. The polymer clay will shrink, but only barely. It shrinks about 2-3%. This is enough to create a small seam between the edge of the wood and the edge of the inlay.

3. You will want to put a coating of glue under your inlay or it could very well fall out later. I use a thin coat of wood glue inside the recess and let the glue dry before putting in the inlay.

Some of this I figured out through trial and error, some I got as advice from Cynthia Tinapple, a polymer clay artist who has created some beautiful collaborative pieces with her woodturning husband, Blair Davis.
 
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a lot is attention is being paid to ignition. That won't happen until about 500F

250 for long enough to cure off a polymer will cause an enormous amount of water transfer out of the wood. That will change the shape of the wood. The polymer is unlikely to conform to such changes unless it goes into a flowing nearly liquid state during curing especially near the end of curing. Meanwhile the cavity it's sitting in will likely get larger and warp. The wood may crack from rapid water loss.

I'd run a test just to see if this can be done. No harm in a test. Take a failed bowl or hunk of lumber similar to the one you might use and incise it for a similar polymer inset and go for it.
What's the worst that can happen? Mrs-You will give you a stern look about the smell in her oven?
 
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