One Force marines, I bought the Forgeworld tactical marines, but wanted to model them with lots of combat weapons as well so that I could realistically use them as assault marines as well with magnetised backpacks. The problem I had is that the tactical marines left hands are all sculpted to be holding bolters, so I needed a lot of left hands to replace them with. Rather than buying even more parts just to get the left hands, I decided to have a go at casting/molding some up myself to see how useful a technique it can be.
I've seen quite a bit about casting/molding recently on the blogs I follow, and from them the posts that I've found most informative and useful are Dark Future Games' post on "Press Molding Necron Scarabs with Milliput and Green Stuff" and From the Warp's post on "Molding and casting shoulderpads".
Based on the information in these posts, and what I had available to me, I decided to try a 2 part mold using Milliput to mold the hands in GreenStuff (have a read of DFGs post especially as to why this is a good choice). I dug out 3 left arms with gun toting hands, cut them off the end of the arm (as I want to retain the detail on the left arms of the Forgeworld armours), and mounted them onto a piece of plasticard ready for molding.
Things to note at this stage, I've mounted the hands in as straight a line as possible which will be necessary for producing the 2-part mold. Once secure, I mixed up some Milliput, and pressed it onto the back side of the hands, taking a lot of care to build it up around the 3 hands so there were no air-gaps around them, and that the Milliput didn't wrap too far around the hands so that they would come out of the mold. Once happy with the matarial around the hands, I also pressed the end of a paintbrush into the Milliput in a few places to make indentations that will be used to align the two halves of the mold. I left this for 12 hours to set up, then repeated the process from the other side with more Milliput to complete the two part mold you can see below.
You can see in the image that the Milliput has retained the details of the hands really well, nice and crisply, and it is extremely hard so hopefully will be pretty durable. You can also see how the alignment holes work to keep the two parts aligned nicely. The benefit of mounting the hands onto plasticard (other than making it easy to handle), is that if I can keep the GreenStuff level with the surface of the mold, then I should have a nice flat surface to attach the hand with once cast. Another point to consider is that at each stage, I made sure to coat all the surfaces with vegetable oil so that none of the materials would stick to each other and I could separate all the parts.
Here you can see the first set of hands I cast in the mold. I inserted the GreenStuff into the mold while the two sides were together, rather than placing a blob of it in and then pressing the sides together. This runs the risk of trapping air in there and spoiling a cast, but it does ensure that the two sides of the mold are properly pressed together without any material between them so you get a close a reproduction as possible. They've come out really well, with great reproduction of the details on the hand. They are very tight in the mold, and I had to apply quite a bit of force to remove them from this side of the mold, but I take that as a good sign as they are tight into the details of the mold so should be nice reproductions. Also, you may note there is a little extra material around the wrists where I've found it difficult to get the GreenStuff level with the surface of the mold, but this is alright as it is easily trimmed and it is better to have too much material, than too little.
I've already attached some of these to figures and although I'll have to wait till I paint them, I doubt you'll be able to tell they aren't meant to be there. Cheers - Andy