resin

wuher da brewer

Sr Member
RPF PREMIUM MEMBER
What makes you think there are no bubbles in the mix? Each time you stir, you're introducing more air. You can use a pressure pot to essentially atomize the bubbles before it sets up.
 

SgtFang

Sr Member
Gone but not forgotten.
<div class='quotetop'>(joeranger @ Jun 14 2006, 10:24 PM) [snapback]1261883[/snapback]</div>
No bubbles in the mix, but it bubbles in the mold, why?
[/b]
Humidity, either in the air or the containers. Sometimes you can bring it back by heating the resin in a sink of hot water, then shaking the hell out of the container to kind of re-mix it, but that'll only work 2-3 times before it gets too bad to use.

Good Luck.

-Sarge
 

joeranger

Sr Member
Sorry about the lack of detail, wife looking over shoulder :unsure

THe problem seems to be the molds. I am using Activa Instamold, but I can't get the lumps out. It turns out like oatmeal, and the resin bubbles like crazy.
The extra resin mix dries perfect in the mixing cup, even picks up the scratches in the cup. I am brand new to this so I am really playing around to see what works. All help appreciated.
 

mr.predicta

Well-Known Member
Humidity, either in the air or the containers. Sometimes you can bring it back by heating the resin in a sink of hot water, then shaking the hell out of the container to kind of re-mix it, but that'll only work 2-3 times before it gets too bad to use.


Thats been my experience as well. I have all my resin refrigerated and well covered in plastic I also try to keep the air out of the container the more air its exposed to the higher the chance of contamination from humidity.opening and closing the container often exposes the resin to water vapor, using a smaller container as you go through the product helps keep the resin from getting screwed up.
also I try to buy only what I will use since the shelf life of this stuff isnt long.
never heard of the resin heating trick but what have you to lose?
 

Beagle Bill

Well-Known Member
If the Instamold is the same product I'm thinking of, that's the problem. It's an alginate powder you mix with water, isn't it? I've only been able to pull copies in plaster or wax. When your resin cures, it generates a lot of heat. This causes the water to leach out of the alginate and "boil" the surface of your hardening resin, ruining the piece. I have heard of a special kind of resin you can use with alginate, but I've never seen or used it. There is also supposed to be a product called "water extendable polyester resin" but I have never used it either. Maybe someone else here knows something about these resins. If what your casting can only be covered in alginate for the mold making process, my advice is to make your copy from plaster, seal it with a lacquer, then make another mold from RTV silicone, then cast resin into the RTV mold. Hope this helps. :)

Bill
 

Fetthunter

Sr Member
<div class='quotetop'>(kevoris @ Jun 15 2006, 12:21 AM) [snapback]1261924[/snapback]</div>
If what your casting can only be covered in alginate for the mold making process, my advice is to make your copy from plaster, seal it with a lacquer, then make another mold from RTV silicone, then cast resin into the RTV mold. Hope this helps. :)

Bill
[/b]

I was going to suggest this, but with the exception of using Monster Makers Oil-Based Clay instead of plaster. You can microwave the clay, thus liquifying it, then pour it into the alginate mold, pop it out once it sets up again (it never hardens totally), then once you have that, just use a Silicone rubber to create your final mold. I use the Monster Makers clay for my original sculpts, Smooth-On's Silicones for my molds and Smooth-On's Urethane resins for my casts, and it all works fine, for what it's worth. :D

Good luck.
 

exoray

Master Member
<div class='quotetop'>(kevoris @ Jun 15 2006, 12:21 AM) [snapback]1261924[/snapback]</div>
If the Instamold is the same product I'm thinking of, that's the problem. It's an alginate powder you mix with water, isn't it?[/b]
Yeah, I suspect that is your problem, urethane feeds on water when it's curing... So you will never get a good cast out of an alginate with urethane resins...

If you ever want a bubbling volcano effect and make a lightweight (lots of bubbles) volcano rock looking mold just add a few drops of water to the resin while you are mixing ;)
 

blufive

Sr Member
Use a better molding agent. I use GI1000 with GI179 activator from Silicones-Inc.com. The rubber must be vacuumed in a vacuum chamber but the results are worth it.
 

Jedirick

Sr Member
RPF PREMIUM MEMBER
<div class='quotetop'>(blufive @ Jun 15 2006, 10:33 AM) [snapback]1262075[/snapback]</div>
Use a better molding agent. I use GI1000 with GI179 activator from Silicones-Inc.com. The rubber must be vacuumed in a vacuum chamber but the results are worth it.
[/b]

Amen to the GI 1000 series. I have found if you pour the silicone into a low point in the form using a pencil lead thin stream from a few feet up, you end up with virtually a bubble free mold. Worked great with a sixteen foot Great White Shark head. Simply no vaccum chambers readily around here for molds of that size.
 
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