recommendations for resin casting

hydin

Master Member
RPF PREMIUM MEMBER
ive done a lot of research on the board, and i have a few things i would like to cast up ( i need monies :) ), so i am curious as to what the "favored" resin is on the board. ive decided to give the dragonskin silicone a shot since it seems to work pretty well (plus buster has yet to tear, always a bonus)

i know about 99% of you will think "SMOOTH ON. DUH.".

they have a LOT of resin products though, so lets try to narrow it down a bit.

what i would prefer it for? reasonably bubble free castings, it can be white resin (dont really need clear right now), and ease of use. in other words, if a retarded monkey can use it, chances are i cant mess it up too badly. i dont have (nor need) a pressure pot. i dont plan to build a pressure pot, and i dont plan to rent a pressure pot. this is for basic resin casting.

so... for relatively small things (nothing as huge as a blaster or phaser), whats the "best" resin to use, and why? (also, if you have a tip or trick or neat factoid about using your favored resin, feel free to share it with the group)

thanks in advance for any pointers guys :)

also, recommended release agent would be cool as well. no need to destroy a mold unless i really have to.

chris
 
I only have experience with smooth-on products, so yes, i do recommend them. For smaller items i use smooth-cast 200 (fast kicking), larger items like small guns, 205 (medium kick time) and the large items 210 longeste kicktime.

as for mold release, i used to use silicone mold release, but nowadays only use talcumpowder. This works extremely well, because of it's capilary ability, iow it 'draws' resin into those smaller areas of the mold.

Marc
 
as in baby powder?

cool.... i hadnt thought about that stuff... i always thought it would gum up the resin pretty badly.

ill have to give it a shot :D

chris
 
yep babypowder, the non-silica kind. Dust the mold and use a soft brush to get it everywhere. Then blow out the excess powder.
 
I know you don't want to use a pressure pot but consider this.

Dusting the mold will eliminate almost all surface bubbles. As soon as the customer starts sanding the seam lines away, bubbles will begin to show.

Just food for thought.

I use Smooth On Smooth Cast 305. It takes about a half an hour to kick but it has one of the smallest shrinkage rates available.

Add a little black dye to make the casting grey. This lets you see surface imperfections easier.
 
Every mold reacts differently with every resin.
For instancee, my fav rubber is dragon skin . If you pour smooth cast 321 in dragon skin with out a pressure pot you will get tons of air bubbles. This is because there is a reaction with the platinum in the mold.
However if you use moldmax tin based rubber you can pour with out a pressure pot and not have any where near as many air bubbles.

Smooth-on has great tech support and a 800 number.
Anytime I want to try a new product they have I call and talk to them and they tell me the results of their own experiments and make suggestions on what products work well.

For instance, ease release 200 can semi rejuvinate an old dead mold. If used on every 4th pull it can extend mold life by 5.

Some rubbers also like to be thrown in the oven for 10 min to get nice and warm.
If you have no pressure pot, this reduces bubbles. I will S PLANE.
Resin cures from a cemical reaction, as it cures heat builds up. The area in the mold that holds the largest density of resin will cure first beacause the exotherm has built up to cure temperature. The thin parts of the mold cure last. The walls of the mold are rubber and rubber is an insulator. So if the rubber is room temperature then the insulation value in the rubber will resist the exotherm heat from the resin for a long time. All the air bubbles that are created during exotherm will keep truckin their way further and further away from the areas of the resin that are starting to solidify. So where do the bubbles end up????? right on the fracking walls of the mold... Why?? because the are nice and cool and the air bubbles like cool fluidic places.

So what the heck does this have to do with heating the mold up?? If you have not guessed yet, the walls of the mold being pre heated will cause the freshly poured resin the partially kick as soon as the resin liquid touches the hot mold walls, there fore putting a skim coat on the walls and allow the resin to cure more evenly. The little fleeing air bubble will start running for the walls and run into this pre cured skim coat and get crushed like they were in the death star garbage smasher.

Ok I need some more coffee now.
 
:D appreciate the info

now, has anyone dealt with polytek or smooth on 300? i was checking out dickblick.com and saw they both were "ultra low viscosity resins" and made "virtually bubble free castings". that and they were pretty cheap.

kinda reconsidering dragonskin for ommoo.

nothing set in stone yet, but the info is appreciated :)

chris
 
I use Ommoo and Smoothcast 321.

No pressure pot, and no sophisticated mixing methods (1:1). So, they're easy products to get used to molding/casting with.
 
I love the Ommoo 30 and the all the smoothcast line. I prefer the 1:1 mixes, makes my life easier.
 
Smooth On 305 is what I use. Again, no pressure with baby powder, virtually no bubbles on the outside but the inside will be loaded with them.
 
would suggest using 1068 Silicone
better tear ratio then dragon skin and isn't as temprimental as DS is

warning to you if your going to use DS, you cannot use or have altex anywhere near it or it will not cure properly or at all

so that mean as nytrile gloves for stiring and pouring

if latex comes in contact with the silicone or the mold
chances are your going to have curing issues

smooth-on doesnt warn enough about that
 
I've used the polytek resin for ages and it has always done the trick for me. Low viscosity and about a 30 minute demold time. Quicker on some smaller pieces even.
 
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