styrofoam sink form

[dave schoeppner]

anyone make a sink form out of styrofoam, just shape it with a sander, and pour it without coating the styrofoam with anything? if so, how did it turn out? i just made one, but i coated it with durabond and an epoxy spray paint. i didnt pour it yet, but i wasn't sure if it was worth the extra work of coating the styrofoam. thanks - dave

[Paul Lundy]

You did the right thing. Coating it with just about anything, even my mother-in-laws death mask would be better then not.

[Ryan Waxman]

make sure its well secured before casting, foam is extremely buoyant, coat it and secure it. I even go to the extreme of using 2x4 over the drain plug to hold it down. I have had a few issues with foam wanting to pull things a part so i use mdf instead.

[Tommy, Absolute ConcreteWorks]

use a good double stick tape to stick the foam down. It won't float, but you need to be careful when you strip the mold. I use foam, bondo and a form coat for lots of our custom one off sinks. You can use raw foam if you plan to gring the surface afterwards.

Tommy

[Mandala Design]

You should really see Tommy gring something. It is a sight to behold.

[Tommy, Absolute ConcreteWorks]

Yes, I love gringing!!! It is my life!! If I had a gringer I would gring in the morning and gring at night. When I get to the East coast, I am going to show Jeremy how the West coasters do their gringing. I have heard that the East coasters do it and say it funny, using a d or something. Silly accents.

Mandala Design said:

You should really see Tommy gring something. It is a sight to behold.

[Alla Linetsky]

I don't bother coating the foam; just sand it to 320 or 600 to make it super-smooth. We still need to grind (or gring, or whatever). And make sure it's extruded polystyrene, not expanded (the crappy white stuff). We hot-glue the foam to the table; 4 good dabs do the trick and release nicely.

If you don't want to coat the plug, make sure that your spackling compound will not discolour or otherwise damage the concrete. There are some vinyl-based compounds that will prevent the cement from setting, and plaster of paris will turn any concrete that touches it very dark. I use a lightweight filler that is available in the US under a different label than in Canada - Red Devil, I think. Here it's called Poly Instafil.

[Expressions LTD]

Hey Dave,
We make our master molds out of either foam or MDF, which we then turn into fiberglass mold parts. If you're looking to make a mold and use it repeatedly, you might consider turning your original into a fiberglass copy first. A lot of the molds we sell were originally customer-requested sizes, so we can turn a custom mold out for you if needed, or help explain the process if you want to try it yourself. When we use foam, we use high density foam to shape the plug, and then coat with Bondo. Bondo can be sanded very smooth, and lets you work out any seams or imperfections on your foam. You can then paint or spray a waterproofing material over the Bondo layer (if needed, otherwise just wax it good). It's a lot of work, but you can get some perfect, very customized sinks this way. It's sad when you de-mold and remove the foam sink because you will probably lose the mold in the process, but the unique one-of-a-kind sink you just probably made should be worth it right!

[dave schoeppner]

good info, thanks!

Expressions LTD said:

Hey Dave,
We make our master molds out of either foam or MDF, which we then turn into fiberglass mold parts. If you're looking to make a mold and use it repeatedly, you might consider turning your original into a fiberglass copy first. A lot of the molds we sell were originally customer-requested sizes, so we can turn a custom mold out for you if needed, or help explain the process if you want to try it yourself. When we use foam, we use high density foam to shape the plug, and then coat with Bondo. Bondo can be sanded very smooth, and lets you work out any seams or imperfections on your foam. You can then paint or spray a waterproofing material over the Bondo layer (if needed, otherwise just wax it good). It's a lot of work, but you can get some perfect, very customized sinks this way. It's sad when you de-mold and remove the foam sink because you will probably lose the mold in the process, but the unique one-of-a-kind sink you just probably made should be worth it right!