# shrinking latex?



## 1031fan (Feb 6, 2007)

calling all the pro maks/prop makers! - - got a slight concern im having with some of my pulls - the latex seems to be shrinking down a bit in size - like the prop is smaller when i pull it than the original sculpt - what am i doing wrong/what should i do to prevent this? also - how long do you usually let a pull cure before you demold it? thanks guys!

riley


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## RacerX45 (Apr 13, 2008)

You aren't doing anything wrong. Latex casts generally shrink anywhere from 5 - 20%. I let my masks dwell for about 2-3 hours (that way they are a little thicker) and I let them cure for a minimum of 24 hours. I cast Batman and Batgirl cowls so I leave them in at least that long to make sure the "ears" are cured before I take them out of the mold. What is your mold make of (assuming plaster or UltraCal 30?).

Randy


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## 1031fan (Feb 6, 2007)

damn - 5-20%? is that why a lot of commercial props seem a little on the small side? - ok - i am letting them cure from anywhere to 24-48 hours so that should be fine - my mold is ultra cal - is there anyway to really prevent it? - my thinner pulls seem to shrink a little more than the thicker ones - but that also means more latex and more $. is sculpting a little larger about the only thing that can be done? - thanks for your help


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## RacerX45 (Apr 13, 2008)

The only thing that I have heard that works is to do the mold in fiberglass and then brush in the layers. The latex needs to air dry with this method so it takes forever to make anything since you have to wait for the layer to dry before adding more. I've never tried this approach but I've seen the results and it does seem to work. If the mold is dry (not used recently) it will absorb the liquid faster and cause more shrinkage. I usually soak my molds before I use them (in tap water) to help reduce the shrinkage. If the mold is wet it absorbs at a slower rate which causes less shrinkage. Other than that all you can really do is make the sculpt larger. Probably not really an option since you'd have to start from scratch. Hope that help somewhat. 

Randy


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## playfx (Mar 10, 2007)

If its just a prop and not a mask you can foam fill it in the mold, this should help from shrinking some, Its a hard call on how much shrinkage you get from each batch of latex and how big you should make your sculpt. If im making a mask i try and go aleast 10% over, prop heads i don't worry to much about. 

Everything Racerx45 said is dead on, also I like to use a pinch of soap in my water when i soak my molds just to take the surface tention off the latex and reduce shrinkage even more.

I've done the fiberglass molding and don't care for it with latex, its more for silicone work IMO but it can be done.


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## 1031fan (Feb 6, 2007)

wow - thanks guys - you both have been a great help - very good info from both of you - i think i will try the soaking idea with some soap and see what happens - i will say that my first pulls shrank more than my later ones - and i was pouring and pulling one after another - made like 5 pulls in 6 days - and the mold was a tad bit damp/moist just from the water or whatever being sucked up into the mold and not having time to dry out in between pulls - so that may what have been happening there - again - thanks guys and ill let you know how things work out - later - riley


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