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Old 10-21-2013, 08:33 PM   #1 (permalink)
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Location: Oregon
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Making a Fiberglass Mold

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?

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