Re: CUSTOMIZINGS Indy, Solo, Drake, Bond etc.
I'm confused with the whole shrinkage thing as some people say only a small percentage shrinks and doesn't make much difference. Not sure what happened with the WGP head though it came out very small from the images I saw. The advantage having a 3d printer is I can always print another if the size is off
Shrinkage depends on what kind of silicon you use for your mold. Resin heats up as it cures/mixes, and it will cause the silicon to distort. Silicon is available in different hardnesses. So, the harder your silicon the less affected it will be by the heat from the resin and it will distort less. I've found that it always distorts vertically across the face, making the face slightly narrower, and you lose the roundness of the jaw/cheek area. It's most noticeable after you pull 10 or so casts. The first 5 or so, you'd be hard-pressed to see any difference from your original.
This PDF from Smooth-On can explain it better. You'd probably want something around 40A.
I've forgotten the numbers by now, but there was a green silicon that I used that was hard(er) and a pink silicon that was softer. And I noticed much less distortion in the green silicon mold.
The way I always saw shrinkage work is like if the nose was a hinge for the two sides of the face, each side kinda curves inward. Shrinkage is most affected by the widest part at the front of the cheekbones. So, if I were a sculptor and printed out a head, I would make the jaw/cheek area, maybe 5% wider than it ought to be. Maybe only barely noticeable in your sculpt in digital form, but it will be enough to account for inevitable shrinkage.
So, I think what you've been hearing is that the cast shrinks maybe only .25%, but on each successive casting, you see that .25% start adding up, and by the time you get to that 15th or 20th casting, you start to see that noticeable distortion.
If you do do the castings yourself, I would strongly recommend Smooth-On 326, it's a clear-ish resin that you can tint to a skintone, very good quality, captures detail nicely. OR if you send it out to a casting service, I recommend
these guys. Sometimes they're a bit slow, but the castings are great.
Also, I just saw
this silicon, I can't recall if it's what we were using, but it specifically states one of it's uses is resisting shrinkage when molding with resin.