Wendy, from Wendies Mini World showed her lovely fireplaces for Hagatha's Skool on her blog...quick go see; they're really nice: http://wendiesminiworld.blogspot.com/2010/02/chimneys-and-roofing-problems.html
Several people commented that they couldn't find PaperClay or had difficulty working with it. You can always order it directly from the manufacturer in 16 oz packages...which is twice the amount you get at your local hobby shop http://www.paperclay.com/
Here are my favorite tools for working with the stuff. The rolling jig was made by my friend, Larry Bolduc from Unicorn Studios. He is a master at PaperClay stonework. See his work: http://www.larrybolduc.com/
The jig is simply a wood frame around a square of plywood into which a square of vinyl floor tile fits nicely. The top of the frame is a scant 1/8 inch above the tile when it is in place. The length of PVC pipe is such that it rides on top the frame, rolling out a perfect 1/8 inch thin piece of paperclay. It's very slick, really. The tile can be removed for clean up and the pipe comes squeaky clean with water.
I treat the papercly like pie crust. If it is too sticky, I dust it lightly with talc; too dry, add a drop or two of water and knead it up a bit. I work fairly quickly with it and always seal whatever I am applying it to first. You can actually used a PVA glue to do this and it serves the second purpose of assuring a good adherence. Remember, since this is an air-drying clay, the "substrate" (your wall or whatever) will also absorb the moisture as the clay dries and eventually warp if not sealed....except probably for 1/2 inch plywood. :-)
Until it has been painted (sealed) you can spray it lightly with water to rework the texturing but after you've painted it, that won't work. I tend to texture as I go and cover the area with a damp paper towel if I am not going to finish at one sitting. I also try to wait to paint until the stuff is completley dry as the paint does two things:
#1. It adds more water back into the mix as I usually uses washes to achieve the "look" I want;
#2. As a result of #1, the possiblity of warpage increases because once sealed with paint, the moisture has no where to go but into the substrate.
I know people who have given up on paper clay because of this but if you take just a few steps to avoid warping, the results are dynamite! It's lightweight and very authentic looking.
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