Fixing a rubber rock mold


WC3026

WC3026

Member
A friend of mine is letting me use his rock molds and one of them has a two cracks in it from flexing it to get the rock out. I believe they are woodland scenic's but not too sure. It is one of the really deep ones and you need to pretty much fold it inside out to get the rock out is there a way to fix this so when you pour in the material it dont come out and to help it from cracking more?
 
If it is a Woodland Scenics mold just buy another one. What I would do short of just buying another mold is cast a rock. Clean up the casting. Seal the casting. Make a new mold using the casting as the master.
 
If you don't want to buy a new one, they can be repaired, but the crack will sometimes get cast into the rock your casting. To repair you need some liquid RTV latex, and a gauze pad or two.

Paint the outside of the mold, after it has been thoroughly cleaned removing all foreign material from the outside, liberally with the RTV latex. Paint some into the crack a little to act as a seal.

When the latex looks like it is setting up, "paint" the gauze, that has been unfolded, into the layer just applied, and seal the gauze with more latex. You may have to paint on more gauze and reseal.

The gauze reinforces the mold and the new latex seals the cracks in it.

I've never tried this method with a deep mold, as it may make it too stiff to turn out. Our club has used this method to repair some rock molds made over 20 years ago from rocks and coal located here. Seems they need repair about once every few years if used heavily.

The advantage to using this method is that you can always make a new mold off of any rock, coal or similar material that you find, as well as repair old molds needing some work.
 
As Carey said it would be a good idea to clean the outside of the mold where the repair will be to remove any body oils and anything else that will not let the latex bond well. Soap and water or alcohol will work. A light scuffing with some 220 grit sandpaper will also give a better bond than the smooth surface of the mold.

To be honest unless I had the liquid latex and gauze already I'd just go buy another mold. They cost about $10 or less depending on the size and where you buy it.

Over time ozone in the air dries out the molds and they get somewhat brittle. Sunlight is another thing that will attack them. I store mine in a zip lock bag with all the air squeezed out on a basement shelf away from a window when I am not using them.
 
Spray the inside of the rubber mold before casting with 50/50 mix of dish soap and water. The casting will pop out easily. I use deep molds with no troubles.
 
You must log in or register to reply here.



Back
Top