Molding & Casting Materials

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A Hunters Moon

New Member
I'm looking into some molding/casting materials and had a few questions. I like smooth-ons mold star 15, mold max 10, or dragon skin 10 medium. The website states that mold max doesn't need a release agent so I'm assuming the others do? Will I also need to seal the clay no matter the mold? I'm using sulfur free van akin clay.


Resin wise it's either smooth cast 300 or monster makers monster cast. With Monster Cast you get twice the product for the price, tempting, but has anyone had any good experiences with it? Also, can I use the monster cast with a smooth-on mold? I mean, I'll go all in with smooth-on if it's the best thing for a project. Just curious about it all.


Thanks to anyone who answers.
 

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xdmray

Well-Known Member
i cant tell you anything about smooth-on. but i do use monster cast resin.
i like it. it kicks in about a minute which i find great for slushing.
 

Philby

New Member
I've used mold max stroke 1 silicone from smooth-on,......doesn't need any kind of release at all ,......just let the resin set all the way ,....it pulls out of the mold easily,........i used just fiberglass resin and it comes out super easy ,......

nothing sticks to silicone except more silicone so ,......but like i said i've only used that combination so far ,....but have not had any problems,....
just make sure to clean out the mold all the way after each cast,......
 

A Hunters Moon

New Member
So what do you guys do to avoid trapped air and bubbles in resin/silicone. It just a matter of how you stir and pour it right?
 

xdmray

Well-Known Member
to avoid airbubbles in silicone, you pour from high above if you are using low viscosity silicone.
if you are brushing it on you need to do a thin beauty coat first. then when brushing it you just have to be vigilant to make sure you are not trapping air. push the silicone around a bit.

resin- i have never had a problem with air bubbles in resin. it pours like liquid. the only time i have to watch for it, is when i lay fiberglass matt in the resin. other than that, it should be bubble free.
 

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Darth Pinhead

Active Member
From my research, the problem you will run into with some silicone products, is that ideally, they need to be de-gassed within a Vacuum Chamber, therefore, I would avoid Dragon Skin. Mold Star is one you can use, as is Rebound 25, which is what I purchased based upon several conversations with Scott Marshall and George, and will be using later this week, along with a UltraCal mother mold.

Another resin you can look into is Silpak. I'm pretty sure George uses a Silpak product (Not sure which one) to make the P1 Stunt Bios. He buys his black (Another good idea, depending on your desired piece, so that if paint chips, if looks like battle damage, versus some crazy color). Hopefully George will see this thread and chime in, or you could PM him to do so, *wink, wink*

As for mold release, I have been using regular old PAM cooking spray, as recommended by George, when I cast my nails with epoxy putty in the Rebound 25. Worked great, washes right off, and is a HELL of a lot cheaper than mold release. The Mold Star info may state that you don't need a mold release, but Pam isn't going to hurt the silicone and if for whatever reason the resin is not curing correctly, you can wash it right out of the silicone with dish soap.
 

A Hunters Moon

New Member
Well, monster makers told me their resin probably wasn't good for what I was doing. Mainly I want to slush a two part mold so that I get a rotocast style item. Meaning a thick resin shell but hollow in the middle. Their resins sets and can be demolded in two minutes time so I'm sure that's why it wouldn't work. At least their honest.

The thing about smoothon resin is you get so little for the price. Looking into silpak today. Any other companies you might suggest for resin?
 

MasterAnubis

New Member
I've used PolyTek, http://www.polytek.com/
There resin seems a little less forgiving as far as ratios are concerned but I started with their products since I could get them locally.
Another draw back is that I think they end up being more expensive then Smooth-On in certain amounts.
I find Smooth-On's stuff much more reasonable when you buy in larger amounts. I've also dealt with Smooth-On reps via Email and found them very helpful regarding specific aplications.

Be sure to check out their YouTube pages since they both make How To videos for their products.


Regarding vacuums...
I de-gas everything. Sometimes you can over do it and induce small bubbles. I also preasure cast everything I can fit into my chamber. That is the way to co with small molds. You can even vacuum small parts molds to make sure resin in in all of the crevices. (Check out my mini bust thread for pics)
 

A Hunters Moon

New Member
It looks like I'll need more mold max than what I can get from the trial kit. Suggested mold size is 1/2 inch thickness around the sculpt. That comes to 1.5lbs of the 2lbs kit and for only one half of the two part mold. Now, can I avoid using so much mold max by makin a master as well? Say, a 1/4th inch mold around the sculpt. Then a 1/2 inch plaster master?
 

Darth Pinhead

Active Member
You have to make a master, regardless. Mold max will not keep its shape on its own; that is the point of the rigid master. Sacrificing on mold max will increase the chances of tearing of the silicone. The best way I have read to minimize silicone, is to figure out a way to make a Cavity Pour Mold. You will probably be better off just purchasing the gallon kit.
 

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A Hunters Moon

New Member
Hmm, okay, I just assumed it didn't need one while watching their how to video. Unless the plexiglass casing they use substitutes as their master. They're also using mold star, if that made a difference. Not sure.
 

Darth Pinhead

Active Member
I shall, at this point, back peddle slightly. Obviously in that video, they are using quite a bit of silicone, more than 1/4", so it would appear that a mother mold is not needed for the reproduction pours. What exactly are you going to mold? Picture?
 

A Hunters Moon

New Member
It's a detailed piece about the size of a paperback book. I was going to use the method in the video but it uses a lot of silicone. Taking that into account I'd still use the plexiglass boxing but make a rubber mold 1/4th of an inch or so thick and then a much thicker master over it to save on material. Something like this . . .

molds.jpg


I dunno. Is that doable?
 

ptgreek

Active Member
wow ..its not really a huge piece to mold ...just make a box mold ...cut foam core into a box with a couple of inches around the sculpt( you can use hot glue to hold the box together) and about an inch or so higher then the sculpt. once the box is made secure the sculpt in the box ...mix up your silicone ( id probably buy a gallon kit ..if ya have some left over, you can mold up other stuff later) power mix the silicone ..then pour it into the box mold at a very high height ( breaking any air bubbles) ..let the silicone set ( oh ..and do all this on a very level surface) when you demold, you will have a perfectly flat backed mold, In this case, I dont even think you will need a mother mold ( big difference between the wording "master" and mother mold BTW) in fact unless you get the mother perfectly flat as well, it would be harder to cast the finished piece
 

A Hunters Moon

New Member
So you avoid degassing Mold Max by using the high pour/thin stream method? I'm assuming you can but wanted to be certain before a purchase.
 

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ptgreek

Active Member
while I myself use different silicons then mold max for casting, I would assume that its properties are roughly the same when just mixed. So yes ...if you dont have a degassing system, a high, thin streamed pour will help eliminate air bubbles
 

Effects Guy

New Member
I just noticed a lot of Smooth On stuff being thrown around. Polytek is nice. I have to say though, if you want a great silicone, that has long shelf life, and great pourability, you should check out 2125 from MPK Enterprises. There site is www.moldmakingsilicone.com, though I usually call up to order. The owner is a fantastic guy, and based in California, but he will ship anywhere. I even wrote a testimonial for this guy, and shipped like 80 gallons of his silicone halfway around the world for some projects.

The best part about this stuff, is their standard blue catalyst cures the silicone in like 2 hours, in 70 degree weather, with a working time of 18 minutes, and does so without leaving the silicone hard or brittle like other fast cats. He has a slower setting one too if you need more work time for big molds.

Sorry to nerd out on this, but you guys who use silicone should definitely check it out. This stuff cannot be beat.
 

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