In the past I have used a two part RTV Silicone compound that used a base and a catalyst to make my molds. This process was an absolute mess. Goop got everywhere, curing time was outrageous, the cost was high and it was just really hard to work with.
In my searching endeavors I have come up with a new way to make silicone molds that I am really excited about. Instead of using a catalyst and a base I am now using a two part putty.
If you are thinking about starting out in casting / mold making this stuff is the way to go. It is super easy to work with. You just pop open the tube, scoop out equal amounts from each, and then mix together. This stuff mixes together a lot easier and faster than green stuff. It is a good thing too that it is fast to mix - you have about three minutes from when you start mixing until it is no longer workable. I mixed up too much on one batch and was going to cast another piece, but the putty had already set. You definitely need a game plan when you decide to mix this stuff together.
One of the best parts of this method is the price. A one pound kit cost me right at $30 shipped. One pound is quite a bit of silicone. So far I made the sandbag terrain mold and a few smaller detail molds and I still have about %20 of the product left. This is a really good value.
The mold you end up with is very tough. You can use it for resin casting, plaster casting, and even pewter casting. I've never tried casting a pewter miniature but I figure it is good to have the option.
I was a bit worried that I wouldn't get a good cast when I squashed the putty onto my mold. I was casting a pretty large piece for my first attempt - a sandbag wall piece of terrain. I mashed the putty onto the terrain piece and made sure to smush it up tight. I then flipped over the piece to kind of level it out and to have a flat surface to balance it on for when I cast the pieces.
After about thirty minutes my fears were relieved - the mold turned out great. The mold picked up detail as well as using a pour in silicone.
The first thing I tried to do with my new mold was to cast it with resin. This ended up not working out very well. The resin that I had was a bit old and had been out in the cold garage. I gave both bottles a good shake (I think this was a huge mistake) and then mixed it together and poured away. It ended up being a disaster.
Here is what I think happened.
When I shook the bottle of amber resin it turned a milky white color. Since there wasn't much resin left I think I aerated it by shaking it. When I mixed the two components together I don't think they mixed well because of all the air. I stirred and stirred until it looked right but I know something was wrong when I poured it in the mold. It was like the two parts had separated. I had a nice mixed part on the bottom and a clear part floating on top of that.
I grabbed a stick and started trying to mix it inside the mold but at that point it was already too late. I let it sit for a while. After a few minutes the resin began to set. After about half an hour it was as done as it was going to get. I pulled it out of the mold and it was terrible. The resin was still goopy in places. The whole thing was sticky and had a very marbled look to it. I threw the piece away in disgust and started cleaning out the mold.
I next tried casting the piece in Plaster of Paris. The casting process went very smoothly. The only thing is the pieces are pretty much unusable on the table. The plaster of paris is so brittle that just rubbing your finger on the terrain piece will rub the primer off. I had to find something tougher.
In the past when I was casting Hirst Arts molds I used Merlins Magic plaster. I got to looking around for something simliar and I came across Excalibur plaster. I ordered in a box of this and have been using it to cast with. So far I have had really good luck with it. In the next few days I will have a post up that goes into pretty good detail about how the casting process is going. There might even be a video...