[BrianB]

Guys, I am price shopping for a RTV silicone with about a 40 shore hardness and decent strenght (ie not tear easily). Does anyone make an economical RTV silicone? I am currently using Moldmax 40 and it's good stuff but is there anything cheaper and just as good?

Brian

[captsully18]

Check out Alumilite's line of silicone. Been using it for a while now, and really like it. Hobby Lobby sells it and if you use their 40% off coupon it makes it affordable. Just bought another tub this morning for less than $20.

David

[BrianB]

Thanks David where do I get the hobby lobby coupon? Also what shore hardness is it? Thanks

[Husky]

Originally Posted by BrianB

Thanks David where do I get the hobby lobby coupon? Also what shore hardness is it? Thanks

BB, there is a way to stretch out the Silicine by 2 to 3 times for little money.
Just pick up Clear All Purpose Silicone Sealant($2.87 @ Walmart for 10 oz's) from the Paint section of Walmart. Lay out beads of it on a clean dry surface. When the beads cure, use them this way;
Skim coat the model with regular RTV. After it begins to set but is still tacky, place the cured Sealant into the Mold Box, nearly to the top, and then fill it with more RTV to join and encapsulate everything. As long as your model is covered with RTV Everything else is filler.
You will hardly notice the stuff and your mold will be as good as if you used alll RTV. I've used it with Smooth-on Mold Max 30 and Hobby Silicone and there was no problem with either of those two.

[SmokeyJ]

Here:
Weekly Specials and Coupon : Hobby Lobby

The 40% coupon isn't available every week, but it does come up fairly often. Bookmark the page and check back once a week.

[captsully18]

Thanks Smokey, I was a little late in responding.

As usual, Husky is very helpful. He also has a tutorial on building molds in which he expresses the same tip he just offered here.

Good luck, and keep us posted on your progress.

Oh, yes. The hardness. Alumilite produces two hardnesses that Hobby Lobby carries. One is high strength 3 (10A hardness) which is the most flexible and should be used when you have any deep undercuts. The other is high strength 2 (20A hardness) which they say should be used when you need flexibility and good dimensional stability. I have used them both and find them both acceptable. Hope this helps.

David

[BrianB]

Husky, I'm trying really really really hard to get a visual of what you are saying. You got pics by chance or a copy of that tutorial? Are you using a whole tube of that Wally world silicone on one mold? Thanks guys for the help! I was actually thinking of using thin wall panel shaped as the shape of the mold box and drill holes in it and pour RTV again over the top and use that as a filler idea but I am too scared to try it as much time as it takes me to prep a prototype in clay.

[captsully18]

With Husky's permission, I would like to try to answer your last question. Hopefully he will correct me if I am wrong.

The silicone you want to buy from Wal-Mart comes in squeezable tubes. Has several names (tub and tile caulk, silicone sealer, etc.) and any of these will do. Squeeze the silicone out in strips onto wax paper (for ease in handling later). Let it cure overnight or until it is hardened. Cut the strips into pieces 1/4" or larger, depending on the size of your mold. Don't worry about waste in this silicone. Any chunks you have left over, put 'em in a zip lock bag for use in future molds.

After you have your form made, mix enough silicone to just cover the master. Let this pour set a little (check the curing time of the silicone you are using) but at about half of the time it should cure, drop the silicone pieces you cut into the mold and pour the rest of your silicone into the mold. This will bond to the first pour, cover all the chunks, use less of the molding silicone, and you will have a solid mold.

Hope this not far off what Husky had in his info. I think I told you that it was a tutorial and I was wrong. I got info from a post of his some time ago.Will try to find it again and let you know where to find it.

David

[captsully18]

Found it. For silicone mold makers. (ATTN MUSKY DAN)

If you cannot get it from the link, it was posted June 21, '07

David

[Husky]

Originally Posted by captsully18

With Husky's permission, I would like to try to answer your last question. Hopefully he will correct me if I am wrong.

The silicone you want to buy from Wal-Mart comes in squeezable tubes. Has several names (tub and tile caulk, silicone sealer, etc.) and any of these will do. Squeeze the silicone out in strips onto wax paper (for ease in handling later). Let it cure overnight or until it is hardened. Cut the strips into pieces 1/4" or larger, depending on the size of your mold. Don't worry about waste in this silicone. Any chunks you have left over, put 'em in a zip lock bag for use in future molds.

After you have your form made, mix enough silicone to just cover the master. Let this pour set a little (check the curing time of the silicone you are using) but at about half of the time it should cure, drop the silicone pieces you cut into the mold and pour the rest of your silicone into the mold. This will bond to the first pour, cover all the chunks, use less of the molding silicone, and you will have a solid mold.

Hope this not far off what Husky had in his info. I think I told you that it was a tutorial and I was wrong. I got info from a post of his some time ago.Will try to find it again and let you know where to find it.

David

Yep!! Also, any rtv that gets stuck in the mixing pot can also get recycled. How's the method work foy you, Dave?
Actually, the Walmart stuff seems harder than my Mold Max 30.