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Mold Making and Resin Casting

The 2 Part Mold
The 2 part mold requires a bit more planning than the single discussed previously. This mold is for any part that has detail on both sides, such as road wheels, figure parts or even whole figures and parts with heavy undercuts that would get locked into a one-part mold.

For this example, we will use a head from a figure that I have been meaning to make a duplicate of for practicing painting techniques, so no better time than now. You can see why a one-part mold would not work on this piece, as the chin would lock it into the mold. Sometimes you can get away with a single piece mold for a part like this if, for example, you only need a couple of pieces reproduced. If you pulled hard enough, it will come out! Forcing a part from a single mold like this would certainly result in tearing of the mold, maybe not the first time, but eventually.

Here is where we will need to construct a mold box. I use a few different materials for my boxes, such as particleboard, Plexiglas, styrene and even Legos!! (plastic building blocks)

We will use particleboard for this one.

The first thing you need to do when making a 2 part mold, is to decide on where to split your part. In other words, you have to use common sense here because you don't want a seam line running across some important detail like a facial feature. This is why on molded figures, you see the seam line running up the sides of the head as it is less conspicuous there and easier to remove. That is where we will put this one too.
Lets use a piece of acrylic for our base. When duplicating a hollow part, be sure to fill any open cavities that are not part of the detail to be molded (Fig 9).
  • fig9

About the Author

About Steve Sherman (bowjunkie35)

Steve is a freelance propmaker (the movie kind) and machinist. A former construction worker, he has been working with tools since childhood. He learned the construction/ metal fabrication business from his Father, so to follow in Dads footsteps was natural. Since leaving the construction industry, h...


Good informative article, very interesting. I've often considered making my own castings but have been deterred by the cost and lack of advice- at least one of those hurdles has now been addressed!
JAN 03, 2005 - 07:24 AM
Informative article, thanks, now maybe I can get rid of those lousy rubber/vinyl tires...... :-) :-) :-) :-)
JAN 03, 2005 - 08:23 AM
Yep, that is what I do also. It's in the article! Thanks Again guys for the compliments. LogansDad, I also use the 10:1 ratio RTV as it is more economical but much harder to use especially for someone just starting out. I used the 1:1 ratio RTV for the artivle for simplicities sake.
JAN 03, 2005 - 08:24 AM
Great article, Steve. I recently made my first attempts at molds and casting, and it seems like fun. Your info will help a lot. Thanks for all your hard work!
JAN 03, 2005 - 01:21 PM
I was trying to use the micro - mark info but it wasn't as awsome as yours. Now I might be able to do some stuff without ruining it., or waste money to just buy one part from a figure set. Thanks for the info. Happy Modeling
JAN 03, 2005 - 04:34 PM
Well thanks a million for sharing all these nice info with us . U really capture the whole procedure in a very good way amd very simpe to follow. Now i just have to come over there and get all the materials , rubber silicone and resin ...... Super nice article Costas
JAN 03, 2005 - 08:04 PM
hi Steve, thanks so much for the great article and very good photos. I felt reading a chapter of a modelling book more than a feature.it was very very helpful. congrats
JAN 03, 2005 - 11:40 PM
Just in time. I'm actually casting a couple of alice packs and German ww2 bergens.
JAN 05, 2005 - 01:25 AM
Wow!! You all are far too kind! It was really my pleasure, but the positive feedback is great. I am getting misty eyed! *tear* :-) :-) Again, Thanks for the comments, they do not go un-noticed!
JAN 05, 2005 - 03:43 AM
it's been said,but still...great info, very well presented, nice tone, am excoted about casting! Thank You!
APR 03, 2008 - 11:28 PM