I had some cans of expanding foam kicking around and decided to make a little experiment to see if it could be used as a mother mold (instead of using fibre glass).
So I started by using a Ghostbusters proton pack fibre glass shell already coated with a thick layer of silicone. I was not sure how the expanding foam would interact with the silicone so as a barrier I covered the silicone with a few layers of aluminum foil. I figured that worst case scenario the foil would stick to the foam, leaving the silicone intact.
After having dispensed an initial layer of foam all over the pack, I used some wooden stir sticks and layered them on top of the foam and then sprayed more foam on top. I did this a few times so that the sticks get can get entrapped in the foam and provide structural support. I used four large cans of foam to cover the entire thing and let it dry and harden for a few days.
It took a bit of convincing to separate the foam shell from the silicone mold once it was cured but I managed to do it while keeping the foam shell intact. The foam stuck to the foil (as I thought would happen). The shell is surprisingly strong and holds the silicone mold very well.
Next step is to actually use it as a a mother mold for the silicone mold when I'll be pouring resin in it.
I'm not sure if anyone had tried something similar before?