Can you make your own plastic sponges?

Is there any product out there that allows one to make their own sponges? Something akin to a 2-part resin product you might pour into a mold and allow to cure. Or does the process of making synthetic sponges require temperatures and/or pressures so high as to exclude them from “hobby” production.

I ask because I am making some custom injection phantoms for the company I work for that have our logo on them. The media that captures the liquid is a sponge encased in a rubber shell. And it would be really efficient if I could cast the shell, then cast the sponge in the cavity filling it perfectly. Currently I have to “float” or embed a piece of sponge in the rubber while it is still liquid. This requires a ton of attention from me during the 1-2 hours that the rubber is becoming solid enough to hold the sponge and not allow it to float to the top of the mold.

Any advice would be great – even if it is that such a product doesn’t exist. Which is what I am starting to think since I can’t turn up anything Googling.



Or…is there a good way to cut plastic sponges?

I’ve seen the hulls of boats filled with an epoxy-type expansion foam, but it got relatively hard, and doesn’t seem like what you’re looking for.

Would you be able to thread some fishing line through the sponge, and secure it to the bottom of the mold somehow to keep it from floating?

No the marine stuff is 95% closed cell, whcih means it doesn’t absorb water, which is why it is good for making boats float. I want something that will absorb water.

I can’t really use anything to secure the sponge to the bottom of the mold, since the bottom of the mold is the (hopefully) unblemished top of the finished part.

The only sort of foamy material that can be done without specialized equipment afaik are polyurethane foams. Essentially they can be mixed, and a chemical reaction foams it while they set (though solvent heat blown PU foams are also used). However inside a mold one has to have a hole for the foam to expand into and push out the air out(and for any excess PU to escape). PU foams can be hard or soft depending on the ingedients, but the chemicals (isocyanates) used to make PUs are toxic and gas masks must be used.

Try googling isocyanate foams for possible suppliers in your area

i dont know if this will help, but i remember watching this old house and they were down in NO working on a house. they were spraying on a fome that they said was open cell. the stuff really expanded to 3 or 4 times its size. it was cool to watch.

Wet it, freeze it solid (the colder the better) and cut it with a bandsaw.

The standard way to cut foam is with a hot wire. You can make one yourself from some Nichrome wire and a power supply. Cuts foam like a hot knife through foam.:smiley: