how can i apply plaster of paris on the ply board? do i need add some adhesiv or pop can directly applied to it?

i was planning to do a mural on a ply board. so i need to apply a layer of plaster of paris as a base coat. So do i need to add any adhesiv to pop or does it stick directly to the board?

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paganwonder7 years ago
Clever idea seandogue!  I like the mechanical medium over the chemical.
There's something to be said for the chemical method. I'm just working from application of a plasterers technique for applying wall plaster. (the first I saw of it was in 1930's home pain to do remodeling when you encounter the steel mesh they used... They also use the technique alot when doing old-fashioned shower surrounds, although the screen used for walls isn't nearly so fine-meshed as insect screening.

I've done quite a bit of traditional plaster and lathe repair on my house and a few others, so am somewhat familiar with mechanical bonding of plaster-type materials, using both screen and lathe.
seandogue7 years ago
Staple common insect screening to the surface of the plywood to provide a porous surface for gripping the plaster
paganwonder7 years ago
Burf's on the right track- two dis-similar materials expand and contract at different rates. For any sort of permanance you need to isolate the movement of each relative to the other.  This problem is commonly encountered when you paint the siding on a house.
For your situation you need a medium that will bond to wood on one side and plaster on the other and remain flexible- I'll bet the paint store (as opposed to the paint aisle at a big box) will have the product you need, they have had the solution to many of my finishing problems.
Burf7 years ago
Plaster won't bond well to wood without a little help.
I have had some success using this method:
To rough side of the plywood, brush on a thin, even coat of 4 parts white glue mixed thoroughly with one part warm water.
When the glue just begins to get tacky, trowel on a stiff coat of plaster of paris, about 1/8" to 3/16" thick and and use a notched trowel or comb to plow scratches in the surface of the plaster. Try not to scratch through to the wood. Let this (the scratch coat) completely cure.
Once the scratch coat is cured, apply a second coat of plaster about 1/4" thick and trowel smooth. Cover with a sheet of plastic and let cure.
This should hold fairly well, but all bets are off if you drop the plywood or strike it hard.