Types of RTV Mold Rubber for Mold Making and Casting, Pros & Cons
Posted by admin in Mold Sunday, 6 November 2011 16:47 11 Comments
www.smooth-on.com to see more video tutorials and image galleries. Examining the different types of RTV mold rubber available for mold making and casting from Smooth-On. Advantages of Latex * Least expensive mold rubber available. * Very elastic, thin-walled and strong. * Lasts a long time. * Offers good abrasion resistance. * Good for making glove molds. Disadvantages of Latex * Strong ammonia smell. * Can only be brushed onto an original. * Many coats are necessary. * Can take up to two weeks to make mold. * Shrinkage. Casting with Latex * Good for casting concrete, wax or plaster. * Generally not used for casting urethane, polyester, or epoxy resins, or low-temp metal alloys. Advantages of Polysulfide * Soft, stretchy, and durable. * Last a very long time. * Moderate cost. * Will cure against water clay or clays containing sulfur. Disadvantages of Polysulfide * Accurate gram scale to weigh components. * Offensive odor. * May stain white plaster during casting. Casting with Polysulfide * Good for casting plaster or wax only. * Will not handle concrete, resins, or low-temp metal alloys. Advantages of Silicone Rubber * Best release properties of all the mold rubbers. * Model surface preparation minimal nor not necessary. * Release agent for casting often not necessary. * Most heat resistance to high temperatures. * Can cast low-tempmetal alloys such as tin and pewter. * High tear resistance. * Knotty tear propagation. * Very good chemical resistance. * Longest mold life …
@slickster3100 All urethane and silicone rubbers will absorb oil.
Ok need a rubber that will withstand gas, oil, and heat any help with this and if silicone will work what will be the best to use ty
Also something to mention about Silicone, since silicone sticks to silicone you could brush the first coat of silicone on the project first THEN come back to it and pour the rest so air bubbles are not a huge problem.. this video is great but the only flaw is the Vacuum degassing machine will scare off ALOT of people.. with a simple brush on coat could take alot of the problem away.. yes a vacuum machine is awesome but at 800-1000 dollars not everyone will invest in one..
@slickster3100 you could just use some brush on silicone?
Thanks for the information. I can tell by the comments everywhere that we can all use any help or information we can get!
I should have taken up basket-weaving instead.
hi can any one help me ty
hi I want to mold a rubber carb boot for my snow machine what rubber would i need for the boot and what would i need for the mold any help ty
@muppetspuppets Hey man, if your´re formiliare with it can I ask you something; do you have to use a release agent/spray for molding with latex? Because I bought a can op Latex Rubber ( I think, the package only says liquid rubber
) and I didn’t use a release agent, making a 2 part mold by the way 
Hope to hear from you soon 
Gr Bob
It looks to me very useful, extremely intersting
It says I can’t pour latex? I’ve been doing this for years, but with a split mould. Did you mean you can’t pour a glove mould with latex? I’d really like to try.
How much will it cost me to make something that Weigh about 90 to 110 lbs use tin catalyzed silicone, platinum cured silicones?