We are designing some masters for casting some rubber characters(toys) that need to be flexible when complete. I have looked all over the web, and cannot find what material could be used for these casting. The final product would have to be pretty non-toxic since they will be childrens toys. I have thought about rubber or silicone. Anyones help out there would be greatly appreciated.
[Are you looking for prototype materials or the real thing? While silicones would work for demonstrating the concept, I'd think they'd be too expensive for the production parts, unless these are pretty small. Flexible toys are usually cast into hot metal molds, using pelletized thermoplastic materials that stick to the inside, are poured out, then further heated to achieve a thin shell without voids. When they are cooled, even undercuts can be pulled out, since the material is flexible. There are some toy-builders hanging around here who can probably give you some more details. For building your working prototypes, you might find Christopher Pardell's 'Casting Positive Forms in Silicone and Urethane' article useful. It's in the alt.sculpture FAQs, on my site.]
For now, we would be just looking for material to make som prototypes. We are nowhere close to production.
For appearance prototypes only you are limited to either urethanes or silicones- they come closest to thermoplastic durometers and strengths- however- of the large variety of compounds that these two categories comprise, only certain platinum cured silicones are 'food grade', i.e. safe to put in your mouth.
Both categories can be pigmented using special pigments, but only urethanes can be had in translucent colors.
If you will need to paint the finished parts- use urethanes and paint them with flexible urethane paints. Christopher
What are some sources for these silicones?
Andrew's website lists lots of sources.
look in phone doirectories for cities where you live (or nearby) under 'Plastics, Molding' or Rubber, Molding' even try looking under 'silicone'
Make sure you specify food grade rubber if that is a concern-
My personal favorite is the products from Silicones Incorporated
<Both categories can be pigmented using special pigments, but only urethanes can be had in translucent colors.>
This interests me Chris, have you had bad experience with the translucent silicones that may companies are touting these days? know the special effects guys are using a lot of it.
Is casting latex in pottery plaster molds completely out of the question? I have never tried this tried and true technique. Apparently, you can get 'ceco'powder, that you can add to latex to build it up as hard as you require. www.cementex.com
I bring this up because latex and plaster could produce a lot of prototype experiments for a small $$$, it is also non-toxic/au naturel. Actually, did you know the latex in the last few years is far more toxic than in the past? The boom in latex condom sales had caused a high demand on the latex trees, they are milked more often than in the past, the tree produces a toxin as a defence mechanism, it is this toxin that causes so called 'latex allergies'.
My experiences with latex as a moldmaking material tell me that it dries as air evaporates the water/ammonia from its surface, so working in a nearly-closed plaster mold would not work past the first layer or two where the water is pulled into the plaster. And then, the latex might stick fast to the plaster. Somebody else is welcome to try this. Chicago Latex sells superior formulations. They are pastel-colored, not rubber band tan, indicating some filler.
The transluscent silicones that I have seen and used are all evaporative cure (uncastable) (quick tip- if it smells lke vinegar- its evaporative cure silicone) Do you know of one that is truely pourable? as to toxicity- if it ain't the purest of pure platinum systems its not good to have it even against your skin much less in your mouth.
again- as an evaporative cure system- latex can not truely be cast except as a thin skin as you suggest with plaster molds (like a halloween mask) Although I have used a latex skin that was then filled with a foam urethane rubber to make animatronic and animation 'puppets'.
The biggest problem with latex for appearance prototypes is that some people can have potentially fatal allergic reactions (rare, but a liability nontheless) This is particullarly dangerous in regards to the Airway- don't put latex in your mouth.
Also- I neglected to mention hotmelt vinyl- which can be melted on an stove or microwave and cast into platinum silicone molds.
It can be had in a variety of hardneses and colors, but produces parts that are smelly- not to mention the fact that the fumes of the molten vinyl are carcinogenic.
Well, I was still wondering if anyone had source of casting silicone? used for these toy prototypes.
OK good buddy! Tell me how they accomplish those translucent silicone gel filled pocket effects? Seems to be affected by gravity or spew on demand? Silicowobble. Where have I seen that before? The breast implanters would love to know (not that I am one of them).
You could try this material, I do movie props and have made hands out of this stuff Ecoflex® 00-30 , its stretchy and durable.
http://www.smooth-on.com/a53/Using-Alja-Safe%3D- Lifecasting-Alginate-to-Cast-Silicone-Body-Parts/ article_info.html
Its a two part mix easy to use.
I've been looking at this product, trying to decide if it will work for my needs. Maybe this is what you're looking for?
Be sure to look all around their site--lots of good products.
Great advice Thank you very much, Potentialenergy and Smackdown
I recommend using platinum silicone - check out DRAGON SKIN from Smooth-On.
Tin silicones exude acetic acid and alcohol - not good for kids toys.
But you must learn all you can about these materials as they are very sensitive to what they get cast into. So you need to make your mold out of a material compatible with platinum silicone. I like using SHELL SHOCK urethane plastic.
You can use liquid silicone rubber to make molds for your products,and the price is also not too high,just $6.5-7.8/per kg.Any more information,pls contact me,e-mail: <email>
I have been trying to figure out the same kind of information. As far as modeling and some casting goes, I think you should check out the DVDs on the Gnomon Workshop website. ( I think it's under sculpture or character design in the site...)
Also, Tap Plastics is a great site that you can order all kinds of mould making equipment and supplies off of. They have a bunch of video tutorials as well. Hope it helps.
If you come across any toy making demos that involve model making, casting, and the ball-joints on action figures, then you should contact me if time allows.
May I know the hardness you required?I mean how flexible you asked?
casting rubber by polytek