Problems with Micro Marks RTV mold

[jkristia]

I know I did something wrong, and I think I know what it is, just want to verify with someone who has used it before with success.

The other day I received the RTV rubber and resin from Micro Mark, and of course immediately I made my first mold. That mold came out all right and I have made a few castings from it. But then today I did my second mold, and it turned out much harder than the first one, and when I tried to remove the cast from it, the mold broke, yes broke. Of course it’s probably because I didn’t mix the correct amount of the 2 parts. So my question is,

Does anyone know how precise I have to measure the 2 parts, and if I have more of one than the other one, which one is best to have more of, the white or the

 

[belg]

I just started doing the two part rtv mold making and read all the instructions and some go as far as to say you should weigh the amounts to get them correct so,I think if your going "with close" enough in this case its not going to be good enough.

Pat

 

[Bill Stone]

I've used the Micro Mark stuff with great success.

I more or less use the "close enuf" method of measure. What I do is use the little paper drinking cups they sell for use in bathrooms, etc. I make a pencil mark on two cups, same distance from the bottom, and use one for each of the two parts --- pouring the contents of the 2nd part into the cup with the 1st already in it. This really isn't very precise but I've had no problems whatsoever. Either I'm lucky or my close-enuf is a little closer than yours.

At any rate, keep trying. This stuff works great for me.

Bill S

 

[jkristia]

I poured my 3rd mold attempt last night, and it came out ok, so I guess the second one was way off being "close enuf"
Seems like I just have to be a little more careful when measuring the amount.

 

[Rusty Stumps]

Be sure to heat the mold before pouring the resin in. I heat mine in a microwave oven at high for four to five minutes. Also, before heating the mold dust it with baby powder and blow the excess away real good. You'll have better results that way. Once the mold is hot you can reuse it with out heating in the microwave just be careful as the resin sets up a chemical reaction and heats very hot itself.

If you get serious about doing RTV molds you want to use the Alumilite RTV material. It doesn't tear like the blue Micro Mark stuff.