My friend just offered to make a concrete countertop with integrated sink as a wedding present. In preparation for this project, I have purchased a used sink that has the basic shape I want for $25. My plan is to make a fiberglass mold of the interior of the sink, and use that to form the integrated concrete countertop/sink.
I've already prepped the sink by waxing with carnuba and have applied a film of PVA as a mold release. Now I'm to the point of cutting the fiberglass and laying it in with polyester resin. Should I cut slits in the fiberglass along the 4 or 5 folds seen in the picture, or would it be better to cut the mat into different smaller shapes?
Should I wet lay it (coat the sink with resin first), or dry lay it (push the resin through the fiberglass mat)?
My plan is to start with a layer of fiberglass, then a layer of thin perforated foam core, and then another layer of fiberglass. Hopefully this provides enough structural rigidity, but if it doesn't I will just continue on with more layers.
I'm using a polyester resin, so adding layers shouldn't be a problem. Mostly I'm concerned with getting the first layer going without any bubbles or other surface imperfections. What are your tips?
