Hello, I would like to try my hand at casting and have a few questions. Do I really need rubber to rubber mold release? Do I really need rubber to resin mold release? Can I substitude the above mentioned for something else? How thick should the walls of my mold be in general for things like tires? I have done a little casting a few times(seats, hatches) but I would like to get all the right supplies this time.

Well, I cast parts on a daily basis. To answer your questions, Yes and No.

When making a 2 part mold, you need to coat the cured half of the mold before pouring the next half. I use vaseline. Just brush a thin layer on. There are commercial products available, but vaseline works just fine. Never pour silicone over cured silicone without a release agent though. RTV (room temp vulcanizing) silicone will cure to itself if no barrier of release is applied and you will have to cut your part out.

I use no mold release agent for my castings for until they start sticking to the mold. The oils in the silicone break down after repeated castings and need to be re-vitalized. Sometimes mold release agents (sprays) can affect the fine detail in your castings. For that reason, when my parts start to stick to the mold, I put them in a 175 degrees Farenheit oven for a half an hour and this will net you more castings. Eventually, your molds will wear out. When pieces of the mold start to stick and tear off on the casted parts, it is time to replace them. Hope this helps.

Steve

Also, for what you are doing, you may want to stay away from 10 to 1 mix silicones. You need a digital scale to weigh each component and if you are off, you have a mess. While they give you more molds for your money, the 10 to 1's are more difficult to use.

Try the 1 to 1 ratio silicones. They should work good for your application. The tear strength isn't as good as the 10 to 1's, but they are easier to use and as long as you don't have alot of undercuts, you wil be fine.

MicroMark has the best quality and best priced 1/1 RTV silicone.

Here is a link to their product.

http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=82083

Smooth on makes a pretty good 1/1, but it is more costly than micromarks.

As far as resin goes, I can supply you with double quantity of what you get from micromark or smooth on for close to the same price.

PM me if interested.

I getting ready to start casting some parts. I didn't know that I could do without the release agent when casting parts.

If you are using poly resin, then no, you don't need a release agent. The silicone has enough oil in it to release the parts just fine. However, you will extend the life of your molds if you start using it after 10 or 15 casts.

As I said before, a release agent sometimes will fill in some fine detail, so if you use any, you just need to give the mold a "puff" from the spray can.

I have been wanting to do that also but it's been a tricky subject and that site at micro-mart is wonderfull instructions. I feel confident I could make a good cast from those instructions.

Thanks for the link

Happy Modeling

I wouldn't worry about a rubber to rubber agent, substitute with some type grease (vasalene, PAM cooking spray....)
As far as how thick the walls should be. They need to be thick enough to hold shape and thin enough to be bendable to remove the end product.
For a tire I would say - 3-5mm all around minimum, better 7 - 10.
Thicker walls will help the mold last longer.

Since I am usually making molds for various parts on a weekly basis and pouring resin daily, perhaps a write up for the features section is in order, a how to of molding and casting if you will! I would be happy to do it. Mods??

I think a write up would be a splendid thing!!

If you need help just let me know.

I would love to see a write up on the subject.

Also, you guys that are new to this. You may already know this and it is kind of common sense, but it still bears repeating. Any time you take somebody elses work, be it a figure, model parts, whatever, and recast it, it is a form of copyright infringement. You are taking someone elses hard work and basically ripping it off. So, the utmost discretion should be taken when reproducing parts. That is, it is OK to repro some for yourself, but never ever offer reproduced parts from someone elses work for sale, big model company or otherwise. Especially something that someone here scratchbuilt and offered for sale.

In the prop world, we call this recasting and the last thing you want to be branded as is a recaster.

Again, discretion is the key here. So, with that in mind, have fun and watch out for a detailed how to in the near future.

Thanks everybody, this is just what I needed to know.

Bowjunkie, I would love to see a step by step article!

well interesting issue there. A whole wrapped article would be super fine


Costas