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Mold Making and Resin Casting

Once this is done put up one wall of your box. Seal it to the base using hot glue. Repeat this all the way around the subject until you have your completed mold box, using hot glue at the corners and at the base (Fig 15). Then seal the clay where it meets the walls. I have found that the rounded end of a paintbrush works best. If you have any gaps here, break off small chunks of clay and press them in using the brush or your flat scraping tool.

Many people build their mold boxes before they embed their subject but I build them a side at a time. The reason I do this? I have found that it is easier to work the clay bed and gives you better access to the sides of your prototype to make sure you have a good clay to prototype seal.

The next step is to make dimples all the way around your clay bed. Use two different size brush ends to make these, making sure not to get too close to your prototype. Make the dimples about 1/4" deep (Fig 16). These dimples will become keys after the silicone is poured and will help lock your mold halves together when making a resin pour (Fig 17).

I usually run a bead of hot glue up each corner of the mold box from the clay bed to seal this area.

That is it. You are now ready to pour your silicone! You can use the same method to figure out how much silicone to use as earlier. Once you have done this for a while, you will start developing a feel for how much silicone to mix. If you are a little short, don't panic. Silicone bonds to itself so it is a simple matter of mixing some more and pouring right over the top of your cured or uncured silicone. I have run completely out of RTV and have had a part sitting half molded for a week and it comes out fine once you finish the pour.

Again, you can use the same process discussed in the single part mold section to measure out your silicone.

Mix in the same manner described earlier and pour (Fig 18 and Fig 19)
  • fig15
  • fig16
  • fig17
  • fig18
  • fig19

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