I first had the idea of making a mold of an HO scale truck and casting models of it when I was browsing the aisles of Wal-Mart. They had some nice HO scale cabs for 4 dollars apiece, and I was planning to build a construction site and a truckstop sometime in the near future. The cabs did not come with trailers, but the local hobby shop helped me out with those. One problem. Almost $10.00 a trailer!! As you can tell from some of my other topics, I am on a pretty strict budget and to spend almost $15.00 per semi truck and buy enough to make a truckstop, a construction site, and fill my roads with a few trucks would cost me a forrtune! My solution: molding. I googled around for some sites that might help me, and I did find one very interesting site. It shows you how to make a 2-piece silicone mold: http://www.b9robotresource.com/molding1.htm
The silicone mold material is the main con. It usually costs around $100.00 a gallon! I found a solution to that too, though. Alginate impression material. I picked up a castingkit baby keepsake casting kit at hobby lobby for 6 dollars (http://www.castingkits.com/proddetail.php?prod=30003), which contained about 3 ounces of alginate impression material. Alginate impression material is a lot like silicone, minus the price. Perfect for me! You mix it in a plastic cup and pour it into your mold, and it dries in 1 minute. You can then remove your molding subject, and you will have a perfect negative reproduction of your subject. I used lego bricks to make my mold box, and the lego blocks have the word lego stamped on each little bump. The alginate impression material picked up such extreme detail that you could clearly read the word lego on the material, although it was backwards. Here is a synopsis of my first attempt at making a mold of an HO scale semi cab (I didn't do it exactly like the website showed, but pretty close to it):
