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silicone molds and smallest resin casting
willc453
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United States
Joined: October 07, 2009
KitMaker: 55 posts
AeroScale: 0 posts
Posted: Sunday, October 29, 2017 - 08:04 AM UTC
Have several boxes of Master Box's 1/35 scale pinup girls that I'll be modifying for zombie/apocalypse dioramas. Problem is all but one of the figures is wearing high heels.
But I have several boxes of Miniarts Afrika Korps figures who are wearing 2 different types of boots, another has a pair of shoes.

Checked and looks like I can add the males legs to the women legs with little difficulty, however I don't want a bunch of legless male zombies crawling around everywhere. Which is why I just tried making a 2 part silicone mold from one set of legs. First problem was when I went to use Smooth On for the 2nd part of the mold, found it had solidified after having bought it just over 3 months ago! But still had some Micro Mark silicone stuff and used that with the result both molds being a bit slick from something. And yes, I did use a mold release on the first mold. Wiped off both molds, but still remain sticky, but hope they'll dry out, other wise will order more silicone.

Here's my question: what's the SMALLEST part you've made a mold of and cast a part from? The leg is basically 1 1/4" long and will be from just above the bottom part of the shorts to the boots. Thigh area is about 1/8th of an inch wide, while the foot is about 1/4". Wondering if the resin will actually make it to the foot area, but plan on using a vibrating table to (hopefully) make it happen.

Suggestions/ideas? Thanks in advance.


RobinNilsson
Staff MemberTOS Moderator
KITMAKER NETWORK
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Stockholm, Sweden
Joined: November 29, 2006
KitMaker: 6,310 posts
AeroScale: 19 posts
Posted: Sunday, October 29, 2017 - 12:33 PM UTC
Sticky silicone after curing: one possible cause is wrong ratio of silicone vs "hardener". Aging could also be involved.

Getting resin into small volumes of the mold:
I have thought about, but not tested, to "paint" the inside of the mold with resin before closing it. This assumes a two part mold.
Adding a "vent" to the toe area to let the air escape could be something to consider. It lets the air escape so that there isn't an air bubble in the toe area. If the pouring funnel is high enough the weight of the resin on top will force resin into the toe area and out into the "vent".

/Robin
goldnova72
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Alberta, Canada
Joined: February 21, 2009
KitMaker: 623 posts
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Posted: Friday, November 03, 2017 - 08:37 AM UTC
Why not just use Plasterscene as the mold . I've made 1/56 scale packs , canteens and ammo pouches using it as my mold . Just press the boots in upside down . Remove CAREFULLY and add resin . Takes a little practice but it works . I use Amazing Casting Resin , which is mixed 1 to 1 , and I've made as little as a teaspoon full so wastage is minimal
Dragon164
#226
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British Columbia, Canada
Joined: February 20, 2012
KitMaker: 1,903 posts
AeroScale: 507 posts
Posted: Friday, November 03, 2017 - 08:57 AM UTC
The smallest item I have successfully cast was a pair of 1/48 scale aoa probes for an f-15! And for filling the molds I use a large gauge syringe.

Cheers Rob.
willc453
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United States
Joined: October 07, 2009
KitMaker: 55 posts
AeroScale: 0 posts
Posted: Friday, November 03, 2017 - 09:30 AM UTC
Thanks to everyone for the replies and tips. Don't believe there was an incorrect mixing amount in either silicone pouring. The first half of the mold was using Smooth On, the second was Micro Marks. Think there was a chemical reaction between the two as the first mold was good, with no stickiness. Never thought of putting an air vent at the foot area to the top of the mold. Used clay around the pants area to create a larger pour area and THOUGHT the resin would work it's way down by gravity. Got the feeling I was wrong on that thought.

NEVER thought of using a syringe. That's one heck of an idea to use on a small mold like this. Will also try coating the inside of both molds, then use a syringe.

Will also give the other stuff a try in making a mold.
Dragon164
#226
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British Columbia, Canada
Joined: February 20, 2012
KitMaker: 1,903 posts
AeroScale: 507 posts
Posted: Saturday, November 04, 2017 - 12:47 AM UTC
Be sure to fill the syringe with acetone as soon as your done that way you can use it again. I usually suck it up through the tip as soon as I'm done let it sit while I put everything away then push it out and repeat a couple times I have been using the same one for quite awhile!

Cheers Rob.