The third casting experiment is now completed, this time with colouring added. The results were disapointing to say the least. Even before it was finished however, I had decided to terminate this line of investigation, since I had learned that I am essentially using the wrong kind of resin. I had noted the distinctive 'boat yard smell', and after a brief e-mail exchange with Mark Copplestone, I came to understand that I should be using polyurethane resin and not the polyester resin which I used thus far. When the third test reached the 25 minute mark, I opened the mold as instructed, only to find the resin was still loose. It came apart like gloopy yellow mud. I left it to dry over night but the damage was done.
Looking back at the first two tests, I find that they are still slightly sticky.
During the course of this project, it hasn't been easy figuring out which products to use. There are myriad types of silicone and resin and they are seldom marketed except under brand names. Hopefully, things will become clearer with time however
Polyurethane resin is said to be much better at holding details than polyester resin. It is also, apparently much easier to work with and isn't noted for its carcinogenic properties.
My next line of experimentation will take place once I've acquired some Polyurethane Resin and, possibly made a new mold. I'm slightly annoyed that I won't be seeing a squadron of assault tanks any time soon, but I'm being philosophical about it. Better to take it slow and steady than wade in quickly and make a mess of things.
There seems to be a conflict of culture at work here. Danish and Garman sites don't seem to want to sell to private individuals where as UK and US sites do. One German site I looked at typified the European attitude thus; "Most polyurethane casting resins are inflammable and hazardous to your health and the environment. For this reason, they are not allowed to be sold to private consumers. You will therefore be required to attach a copy of your business license or proof of your status as a professional when ordering this product."
Talk about conforming to stereotypes.