My son and I are in the middle of building a Jurassic Park Explorer (exactly like the 1 from the movie) and I am currently focused on the roof. I’ve made a mold out of Styrofoam and have just put the 1st coat of USG Eazysand over the whole thing. I want to finish off the plug with Plaster of Paris because it is much harder and can handle the heat & pressure of a ¼” thick sheet of 350° Acrylic being thermally draped over the top of it. My question is what do I need to do to make sure the Plaster of Paris adheres to the USG Easysand? In my 1st attempt at this, I only used PoP – final sanded the first coat with 40 grit paper- but because I didn’t know what I was doing, the 2nd coat did not adhere to the 1st coat and completely cracked back off. This time I opted to use the easysand for it’s lengthier work time, but I need the final coat to be PoP. Do I just rewet the surface of the easysand or do I need to roll on a bonding agent? If so, what kind? Thanks, Greg
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Well,
I have no idea of what you are building but.....
I use Plasterweld to bond joint compound to plaster if I fear poor bonding.
I use concrete glue for skim coats and minor fill repairs on concrete.
Try one of those on a mock-up test sample before you use it on whatever you’re building.
And do post back with a finished picture of whatever you’re building.
A. Don't use Plasterweld. It's made for another purpose.
B. Compound any type - will only properly bond to a DRY surface.
C. Plaster will only properly bond to a damp surface.
D. To get the plaster to bod to the compound, paint the compound with a coat of alkyd (oil based) primer. Let dry for 24 hrs. Apply plaster.
E. Do not use a water based primer - acrylic or latex. They will peel off the compound.
Frankie
Frankie,
My suggestion on the use of Plasterweld does indeed work for bonding joint compound for adhesion problems to plaster. I’ve done when needed several times and it resulted in no more problem.
Of course since it wasn’t on whatever he’s building I suggested a trial run on something else.
But, that’s what this board is all about, discussion.