Check whAteyecando s thread for his homemade frag blocks...He made his own concantation of portland cement and sand.

Haven't made the mold yet. Was a late night :s

Basically silicone in a giant blob will take a long time to cure so by adding the corn starch to the thinned down silicone it cuts the cure time to a couple hours

So I heard about the corn starch from a few different sources online...

Tested it and the corn starch did nothing for the cure time so I went ahead with a method that I had used in the past that worked well for me... Mix the thinned silicone with a bit of water :). Dried to the touch within an hour throughout the whole 2" thick block ( I cut it in half to check)

So now all I have to do is buy some more rtv silicone and make my final mould now that my "tests" are finished

So, you thin down Silicone 3:1 with paint thinner and then mix water into it to accelerate the drying?

Can you please elaborate on this?

Pretty much

Rtv Silicone cures through exposure to moisture in atmospheric air, because I'm creating a giant "blob" of silicone the center does not get exposed to moisture. By adding a small amount of water to the mix it exposes the inner parts of the blob to water allowing it to cure.

Also I used xylene as a thinner as I have lots laying around

There's an easier way too... But two part silicone :)

Buy...

I assumed that he was using 2 part RTV to begin with.
This would be a bit cheaper if it works.

Nope, I'm just using all the half tubes of silicone I have laying around

First attempt with one of my test moulds

http://i11.photobucket.com/albums/a1...ps89fd0196.jpg