Difficulty Keeping a Mold Water Tight

[JLeague]

I have a 8"x6" mold that I recently finished, and upon filling it with water to approximate the amount of resin needed I noticed it won't hold water very well.

The gate I created at the bottom of the mold is only about 1/4" from the edge and I'm concerned that might be part of the problem. I also use rubber bands (size 64) against a cardboard backing, and while they stretch fairly well they don't seem to be as tight as I would like. Doubling the bands creates a bit more stress and I'm worried about warping the casts or damaging the mold. ...I never anticipated researching rubber band sizes, but here I am.

I'm curious if this is as simple as getting the right size rubber band or if I'm in trouble as a result of my gate distance to the edge? I'm also curious if the viscosity difference of the resin might prevent it from leaking versus water? If it's the gate distance to the edge, I'm wondering if anyone has any suggestions? I'm willing to add a little to the bottom but I'm not sure it will work.

Thanks for reading, and any help would be greatly appreciated.

 

[BJohn]

What I did on a mold I made was for the first time just used some frog masking tape (painter tape) on the seams. After the first time the Alumilite (if that is what you are using) will fill any cracks or voids and you should not have anymore problems.

 

[Olsarge]

use a small amount of plummers putty between the pieces of the mold till the first pour.

 

[JLeague]

Thanks for the tips guys, I really appreciate it!

 

[TimS124]

My worst leak was about the third or fourth time I used my first mold...turns out, I didn't get one of the screws tightened properly and didn't notice it until I started pouring in the mixed resin. Yeah, that made quite a mess. :biggrin:

Water is much thinner than mixed resin, so I would expect it to leak faster than your resin...

Which resin are you planning to cast with? For Alumilite, there are two easy options:

1) use Alumilite's volume calculator: Volume Calculator

2) Figure out the volume (in cubic inches) of the resulting block you want to end up with and multiply that by 0.554. That will tell you how many ounces of resin you'll need to use. You can find the details on that in the fine print on the volume calculator page...

 

[Marko50]

Amen

use a small amount of plummers putty between the pieces of the mold till the first pour.

Amen to the plumbers putty. It will save you copious amounts of grief.