So I asked this in Keyboard Key Caps, but I thought this might be a better place for this:
I'm looking into making my own keycaps now, and I've got some designs in clay ready. Looking to buy silicone for the molds now, and resin for the caps themselves. I've looked at guides that are up on reddit and here, but I need help with some clarifications.
So for silicone:
- [size=78%]Should I be looking for harder and softer molds?[/size]
- [/size][size=78%]I have two options right now, and they're both alumilite products, which seem to be well touted by those making artisans.[/size]
- [/size][size=78%]Product A: Takes a bit longer to set but it comes out softer and more flexible.[/size]
- [/size][size=78%]Product B: RTV Silicone, sets more quickly and, to my understanding, sets harder.[/size]
For resin:
- [/size][size=78%]I'm at a loss here. I don't know which type I should be looking for.[/size]
- [/size][size=78%]My main question is: how long should I be looking at for demolding/hardening times for the resin?[/size]
- [/size][size=78%]All the ones I've found in hobby stores are "super-quick set" and are done in 10 minutes, but people's guides and logs show that they usually take 24 or more hours before demolding the keycap.[/size]
- [/size][size=78%]Is there any specific compound I should be looking for?[/size]
Any help would be appreciated guys, and I hope to share my (or rather our, since this is actually a project with another user here) work with you all as soon as I (we) can! 
for silicone:
I only have experience with one kind of silicone, thats QM 262, which was recommended in
this guide, you can buy this from Hobby Silicone. Works great for me, its a platinum silicone which from what I understand is better for precision molding due to its very slow shrinkage, but a little more expensive. Its a fairly hard silicone but won't rip and is flexible, which is fine for small applications.
for resin:
I've ordered my resin from BJB, im currently using TC-857.. its clear but doesn't classify as "water clear", but it sure is close. No fumes (to my surprise) and an 8-hour demold time... which i recommend you extend to around 20+ hours. I've had alot of caps stretch, or break while demolding, and found it a lot better to just wait until they are mostly fully cured. I've stretched / broken alot of stems when demolding too early.
Again BJB was recommended by the guide above, and they are one of the few companies that sell to the public.
I don't have experience with very quick setting resins, nor would i want to. The resin i use has a 8 minute working time, and frankly i could use more. That 8 minutes for me is...
pouring/weighing
mixing (thoroughly)
degassing (this can take a few minutes)
extracting and injecting into the molds
loading into the pressure pot, sealing and pressurizing (again, a few minutes to get pressurized)
Even with 8 minutes, as im injecting sometimes, i can feel the resin start to gel, and if its gelling as you're filling your molds, its harder to get it in to those looks nooks and crannies in your mold. If you're pressurizing your mold, then you want that mold to be as viscous as possible when you start your pressure.
For picking your resin, I would have a look through BJB's (or any other resin makers) data sheet. BJB's at least tells you the setting color, the working time, demold time.. etc. As for what kind of compounds, I think for caps you would want a rigid polyurethane.
If your demold time is 10 minutes, your working time couldn't be more then a couple minutes, and that's just not enough for these small applications, at least for me.
Hope this helps
let me know if you have any other questions
