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135
Mold Making and Resin Casting

To start, we need to make a clay bed under our subject for support. You want these supports, or "pillars" to be 1/2 to 1 inch high, depending on the size of the piece to be molded. (larger pieces require more clay for support as more silicone, thus more weight, will be on top) (Fig 10) The last thing you want is for your clay bed to collapse once your silicone is poured) By suspending your prototype, you are also allowing air bubbles to rise away from it more easily to what will eventually be the outside of the mold.

Next, use similar sized pieces of clay to build your bed outwards (Fig 11). Remember that we want about a half an inch space between the sides of our box walls and the prototype.

Now that your part is suspended from your base, use fairly flat pieces of clay and start sealing your part at a right angle to the clay. Work a side at a time, sealing as you go. I just use my finger here to "rough in " the prototype (Fig 11a).

Use a flat scraping tool (I use a bent, flat file, sanded smooth and with rounded corners) to be sure that your clay bed is sealed against your prototype (Fig 12). Try to be sure that you seal the clay at right angles. In other words, try not to have your clay at an up or down slope.

Once your clay is sealed all the way around to the prototype, it is time to clean the part of any bits of clay that will affect the mold. Use your scraping tool to remove what you can, and then use a brush dipped in rubbing alcohol to clean the rest (Fig 13). Rubbing alcohol will dissolve the clay residue left on your part to insure that none of the detail is lost. Remember, your silicone will pick up every bit of detail including bits of clay!

Use a hacksaw blade to cut each side square as shown in Fig 14.
  • fig10
  • fig111
  • fig11a
  • fig12
  • fig13
  • fig14

About the Author

About Steve Sherman (bowjunkie35)
FROM: IOWA, UNITED STATES

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...


Comments

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