Title. I’m looking for resins with the lowest Shore hardness, the lowest one I’ve found (that I can buy on aliexpress) is Resione F39, with Shore 60-75A. Ideally, I’d want to get something closer to Shore 30-40A.
So, failing that, anyone with a higher understanding of chemistry can explain what additives are usually added, resulting in a cured resin with greater elasticity?


Could you perhaps print a mould and then cast platinum-cure silicone in it? This can be a pain, as lots of resins contain things that stop silicone curing, but some combinations work (e.g. some bbdino silicone I had cured just fine in contact with Sunlu ABS-like clear blue resin I had) or can be made to work (e.g. coating the resin mould with something that it’s more compatible with).
If you don’t need the properties of platinum-cure silicone, you might even be able to get away with tin-cure, which is much cheaper and more tolerant of other chemicals.
I’ve made silicone moulds with resin prints. The key (for me) to let the print off gas for about a month and the cure inhibition is gone. But not everyone has a month to wait.
I’ve been trying to make/print a usable mold of the model, but due to its irregularity, i’ve been having a hard time doing so in blender, even with metaballs
If you’ve got a manifold mesh for the object you want, you could make a mould by getting a cube that contained it, using a boolean modifier to subtract the mesh from the cube, then adding one or more cylinders for pour holes at the high point(s) of the mesh and subtracting those, too. If you only need one of the object, so don’t need to reuse the mould, you can stop there and print it, then once you’ve cast it and let the silicone cure, just hit it with a hammer until the mould smashes and the silicone will probably be fine and pull out in one un-scarred piece.
For the size I want to print, a pure cube won’t cut it, but I did manage to make a form-fitting mold by making the cube hollow, then removing the cube proper, being left with the mold proper.
I’ve been spending quite some time trying to figure how to properly cut the mold into 2 or 3 parts in a way that I can actually close the thing and pull out the cured silicone without it deciding it’d rather stick to the cured resin. I’ve given some thought on making a single use mold, but I also gotta figure how to ensure its interior gets enough release agent to help me demold.
Can you share the model here? I can take a quick look. If you’d rather not share into the wild, then direct message me
I’ve never needed release agent with platinum-cure silicone as it’s not stuck to anything except itself unless it was porous. I have needed to lubricate bits of moulds that would have had too much of a vacuum if just pulled, though. Also, when I initially referred to coating the mould, I didn’t mean a release agent but rather something like PMMA (acrylic) dissolved in acetone to protect the silicone from the resin as described here: https://blog.honzamrazek.cz/2022/07/preventing-platinum-cure-silicone-cure-inhibition-in-resin-printed-molds/