IbuildScaleModels

Pete, I was asking to confirm the details of naphtha and mineral spirits being the same thing. From what I see, they can be the same thing sometimes but not always. But the lighter fluid is a good substitute and easily available here. Also from the wikipedia page, it says coleman camp fuel is naphtha also. Again, readily available. thanks!

Pete, can you confirm? https://www.thespruce.com/mineral-spirits-vs-paint-thinner-difference-4764584

lighter fluid... interesting.... ok. I actually have some at home on the shelf... back to the drawing board.

From what I read about naphtha is that it is a mineral spirit with higher purity and faster evaporation rate. Doesn't sell here in Montreal from what I saw. You can use mineral spirits/naphtha to either shrink or grow a mold. Also silicone molds shrink over time and you soak them in mineral spirits to get them to grow. I'll look into it more Pete, thanks for your help!

hahaha... I've heard that exact comment too many times. I have also heard I should work for Microsoft or Nasa. Just not interested... Also the corn starch with the rubber does harden it. Tested it last night. Unfortunately it makes it too brittle. I will try today mixing the starch with the mineral spirits first to make a thick syrup base and then mix the RTV rubber in it to see if it will work. Unfortunately mineral spirits greatly increases the drying time. If I had a vacuum chamber I would be able to do a more accurate test. Luckily, the corn starch in the silicone makes the mold super solid and gives it great detail. I think I will use a gloss spray coat on the silicone as a mold release instead of a vaseline (petroleum jelly)/mineral spirit mix like they use in cinema prop molds. the petroleum jelly causes the mold to lose some definition as it is adding an extra layer of interference. Maybe if I airbrushed it on it would work better... Just thinking out loud right now.

Thanks Noel. Unfortunately I can't find it in pdf format and will have to order it unless someone can photograph just those pages for me. MY 2 part mold works... sorta... but its the hole that is driving me nuts and I understand that is where the 3 part mold comes in. just driving me batty trying to figure this out. and my new mold test works great... good ol corn starch with silicone to act as a catalyst and hardener. might try it out with the rtv by mixing in mineral spirits to thin it but also mix in a bit of starch to help it become a bit stiffer. Forgot to put a vent port in my mold so that makes it a fail. Good old home supplies to help in the build process!

Awesome! thanks Noel... going hunting for the book now

Do you still have the molds kicking around? I am looking around for 3 part mold tutorials. I'm just not grasping how to do it for the tires. I would prefer the pour line / tree joint to be on the inside of the tire to leave the tire im casting as much in place as possible. Maybe im just not understanding how to do it properly and could use your or someone else's assistance in doing so. Hell point me in the direction of a good tutorial on how to do it it even and I'm happy. Thanks.

Richard, again... I'm lost on the 3 part mold. I'm trying to figure out how to get a good impression in the silicone mold from the tire and then finding a way to make a port hole to pour the rtv into. Please do share your process with photos.

ohhh please share a tutorial on your mold making process!

i used kleenflo rtv gasket rubber. It feels too flimsy/spongy versus harder rubber. I know it is all in the preparation. maybe need to degas it or let it cure longer. Don't know... still doing tests. Pete, duly noted. Again, still testing things out. Also, what is available to me on a limited budget isn't a lot. The 2 part silicone, and urethanes are more expensive in Canada (from what I have found) unless i buy in large quantities.

Found the "trial-size" of casting resin. Yah, already used this stuff. Expensive for the size. I have to improve my castings first.

I am using RTV in small quantities, but it makes the tire too soft. I want them stiffer. Using resins is out of my budget... buying a sherline broke the bank... Again, not trying to make them soft, trying to make them harder. I am looking at the chemistry actually. I am using silicone caulking to make my molds and using RTV to make the tires. But the RTV is too soft. Buying large quantities when I haven't tested a method is pointless and will run me into the ground. Instead, I want to test out several methods before actually investing more money. Hell to get 1 gallon of 2 part resin in canada will cost me close to 200-300$ shipped. Not worth it in my opinion if I can find cheaper alternatives that work. But yes, I am aware of the more expensive tried and tested methods. Unfortunately, I have to go the DIY/scratch building route on the cheap.

Man, making rubber tires... new scratchbuilding territory. Have to make a silicone mold, and then use HTV rubber sealant for the tires. Unfortunately forgetting to put a release agent is not fun. Also, need to find a way to harden the rubber a bit. Going to try a bit of CA in the rubber mix and hope it doesn't catalyze too fast. It probably will.. but hey.. that's what this is all about. HAHA

Nice! Good references! Thank you very much!