Casting problem

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r1237h

Member
Joined
Mar 30, 2012
Messages
44
Location
Port Moody, British Columbia
Used resin saver molds, silmar 41.

Put in the hardener, mixed and poured, one side totally hard, the other side hard except for a soft layer on top. Only reason I can think of is that I used a toothpick to get the last of the silmar from the sides of the small cup I mixed it in, and perhaps there wasn't hardener there?

Sodo I wait more, and hope it hardens without hardener, or just wipe that layer, and turn?
 

Sylvanite

Member
Joined
Jul 18, 2006
Messages
3,113
Location
Hillsborough, North Carolina, USA.
Exposure to the open air retards the cure of polyester resin. That's why PR castings will be dry to the touch on the sides and bottom, but remain tacky on the top. The surface will harden with time. Mild heat (such as sunlight) will accelerate it. You can also put an air barrier over the top (wax, PVA, or even plastic cling wrap) for a quicker surface cure.
 
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