(this is the 2nd part of Fun with Silicone and Foam)

So now that we had our silicone moulds ready, we had to start figuring out the foam part.

The foam we got (ProCell S5) had a mix ration of A:B of 3:1 by weight (beware that some ratios are given by volume and some by weight, so stay sharp and RTFM). Since we had no idea how much the volume would change once the foaming reaction happens, we opted to do a trial with 120g A and 40g B:


The result was a lot of fun to play with 🙂

The volume looked to be about right, but just to be on the safe side, we decided to use 150g + 50g.

So we went at it…

Just as a reminder, this was the goal:

hard rubber gun

And this is what we got:


So, what happened?

  • The foam cures very quickly (20sec). We were too slow pouring it into the mold.
  • The color we added changed the properties of the foam (made it more sticky and increased viscosity). It behaved differently with color than without.

Off to the next try, this time with more speed and less added coloring:


Slightly better, but still very sticky (and it remained sticky for hours), not very precise and not fully formed.

Since we were suspecting that the color was screwing us up, we tried one without any additives:


Well, what can I say, it worked beautifully…

So we decided to give the color one last try with WAY less color (basically just a few drops):


Not too bad, it actually worked quite nicely, however, the foam actually managed to push the two mold halves slightly apart, that’s why there is a massive seam on the top of the weapon (our mold support was quite bad, basically just the silicone forms held together with two pieces of metal and some string):


Now that we kind of went through most mistakes at least once, I think our next few experiments are going to be more successful… maybe.

Once the foam props have fully cured (a few days from now), I’ll probably post pictures of how the final versions look (with some shiny lacquer and maybe some additional paint).