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135
Mold Making and Resin Casting

Now we will pour resin into both of the molds that we made earlier. Form a pour spout in the plastic cup that you will pour from and carefully fill the mold(s) with resin (Fig 30). In certain situations, for example, if you have a part that runs long horizontally, you may want to make 2 pour spouts instead of one to insure that the mold gets completely filled. A turkey baster works really well for pumping resin into hard to reach areas of a closed mold. You will know they are filled when you see resin come back up through both the vent and the pour spout.

If you have a pressure pot, put the molds in now and pressurize to 60 psi. A pressure pot works by "squeezing" the air bubbles so tight, they are microscopic, and thus you get cleaner castings.

Warning: Never try to make a pressure pot out of homemade items such as a pressure cooker. Only a pot rated for this psi should be used and it needs to have a locking lid.

A home made pot with an improper psi rating can explode, sending shrapnel in every direction, causing serious injury and yes, even death!

I have found that if you plan your pouring and venting system carefully, you will only need a pressure pot for the most complex, detailed parts, and even then, it is not necessary, but expect to do a little filling of air bubbles. Here is a tip for filling air bubbles and pinholes. When I get air bubbles that need filled, I usually put that part aside until I make another pour. After you do this, you will have some resin still in the bottom of the pouring cup. Wait until this gels and using a stirring stick as a spreader, fill the holes in the affected piece.

Once poured, you will see, in about 5 minutes, what we call the "bloom". That is the catalytic reaction between the 2 parts, which causes the resin to harden. You will know that you mixed your resin properly when you see this (Fig 31).

After 30 minutes, you can remove the parts. Remove the rubber bands and support pieces and separate the 2 halves on the 2 part mold. Gently flex the piece and it will pop right out. On the single part mold, I usually apply a little upward pressure with my fingers from the bottom of the mold to loosen the parts up (Fig 32).
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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