Casting a plaster mould form a plaster master.

[JANDERS10]

Hi,
I need to get the best results casting a plaster mould (because of size/price) from a plaster master, 1metre x .5metre x.3metre

I can re-enforce for strength, but its the sealing and seperation of the two that worries me.

Anyone have any experiance of this ? Any advice welcome.
Cheers,
N.

 

[Jaruemalak]

Once your master is dry, spray it down with a couple coats of clear varnish or polyurethane sealer. After a couple days spread a thin layer of petroleum jelly over the mold. Heating the jelly to melting and working fast and thin with a paintbrush works well. Another thing you can do is mix the jelly with alcohol or acetone and spray it on with a paint sprayer. Now, add the plaster for your casting. I've used this method for years and never had a problem.

There are other release sprays (like silicone release) that work well as well. It really helps if you seal the master first.

 

[JANDERS10]

That sounds like a plan, thanks for the advice.
re. sealing the master, I imagine something like ordinary gloss paint should do?(there are no fine details)
Cheers,
N.