: This board was a wealth of information for me when i was building my kayak,
: now I'm hoping the resident fiberglass/resin experts can help me with a
: slighty OT project. I want to make a fiberglass mold of an original
: sculpture I've carved out of foam. My plan is to seal the prototype, coat
: it with a mold release and then use polyester (cheaper than epoxy) resin
: impregnated fiberglass to build up the mold shell. My question is if I
: could use unfaced fiberglass insulation (maybe 2" thick), satured
: with resin, to build up the shell quickly and cheaply? Or do you think i
: should stick with multiple layers of good old 6 oz. cloth?

I will put this idea out just for something to think about, because it does take some technec. At Fisher Body we would prepair, say a fender of a car model in this manner. First your prototype must be sealed. Then we greased it with Crisco and wiped off the excess. Then we brushed on a coat of ultracal (A type of plaster). When that partially set (thickened) we gently pored on coat of ultracal to thicken the surface coat. When that set some and thicken even more, but not dry, we dipped hemp for thrength from bales somewhat like hay, into new mixed (plaster, ultracal) and layed it on the surface coat gently so as not to mar the surface next to the mold. This makes a very strong mold and cheap. The surface plaster cannot dry out before putting on the hemp layers or you won't have a good bond. The first brushing is to help eliminate bubbles, but we used vibrators to do this also. Just an idea for you but timing is everything with this process.

John