A FWIW For Silicone Mold Makers.

[Husky]

On reoccuring theme I see when RTV Silicone is mentioned is expense. The amount of expensive Silicone you use can be reduced by 2/3's by adding one simple step.

Set you mold up in the normal fashion BUT, only mix enough Silicone to barely cover the model. Once that sets, mix 100% Silicone sealant with water (Walmart's Mainstay, $3 for a 10+ oz tube, sold in the paint section is MOST EXCELLENT) and fill the remainder of the box with that. It'll set in under 20 Minutes.The resulting mold will do everything one made with 100% Expensive RTV will at a fraction of the cost.

BTW, you can do the same with all RTV Silicones, even the High Heat ones like Dow Corning 3120. Anything that is not in contact with the model is filler and as long as the Sealant isn't in direct contact with the casting, it'll stand up to as many pours as the 3120 will!

FYI, you can determine how much Silicone is needed by estimating your needs using 20 gms of silicone per cu in.

Edited September 4, 2009 by Husky
Senior Moment

[Husky]

I've been hit with one reoccurring question;

How much water?

To assure an even and sufficient mix:

There is no specific ratio as the silicone will only take on a certain amount of moisture. One good way to apply the water is to spray it over the silicone, mix it in then do it again. Moisture is what causes the Sealant to cure but there is no prescribed ratio. Spraying the water gives a better chance you'll get a good, even mix.

And that's what I learned at Hammer Mechanic School.

[captsully18]

Thanks Husky, got a couple of new molds coming up and will try your advice. Haven't found you to be off yet. Your advice that is. All of us are off to one extent or another or we wouldn't be here I guess.

Thanks again.

David