Having some Smooth-Sil 920 Issues...

[Kylash]

Alright, so i got 2 big gallon tubs of smooth-sil 920 that ive used on and off over the last 7 months or so. Recently, its been getting where molds im making are curing fine on the outside, but on the surface of the piece thats being molded, the stuff is staying tacky.

Sometimes its only on certain surfaces, like i had 3 identical items but 1 of them had a tacky molded surface on the mold, the others were dry and fine.

Ive made sure to mix both parts good before mixing together, but maybe i just need to mix them up more after sitting so long? Im about to mold a sculpt ive been working on for months and i want to avoid this hapening when i do that.

thanks

 

[madrobot]

Certain kinds of primer will cause your silicone to not cure properly.

Anything with lacquer thinner that isn't 100 percent dry, will do that. Typically I would take any pieces I made, and leave them sit out in the open after painting for about a week to ensure that the primer had completely cured.

 

[Kylash]

thanks, that might explain the 3 items i painted. However, ive had this happen on items that arent painted at all and have no finish =\

 

[fettster]

is this smooth sil an rtv silicone? if so, mix it to within an inch of its life and add a couple of drops of acrylic paint and mix somemore.

rtv uses moisture in the air to cure so i can only imagine the outer surface is curing and preventing any more moisture to get through, by adding the paint, you are actually mixing alittle water into the silicone so it all has its own supply of moisture to use.

hope that helps

 

[Kylash]

i think its Platinum Cure

 

[fettster]

i think its Platinum Cure

if its platinum, it will be a sentitive silicone, avoid contact with any thing latex or sulphur based. the acrylic paint trick will work with plat silicones too