Dear fellow modeller

I have a problem, which I hope one of you can help me with. I have for some years now been casting my own parts in resin. In many cases this is done in a two-part mould. In order to get the details more refined I usually brush the resin into the finer detailed part of the mould before putting the two halves together. This leaves, however, very little time to put the remaining resin into the mould before it starts hardening.

Is there any kind of “additive” that can be added to the resin to prolong it’s “pot life”? Or does anyone know of a kind of resin that has a fairly long pot life, say like 7-10 minutes or so?

If you have any suggestions for this, or another advise I’ll be grateful for your help.

Kenneth Østergard

there's no additives. you'll need to find another resin with a longer "Pot Life"

Smooth On offers several "pot life" lenghts and 7-10 is the one I Prefer. Contact a Distributor you should be able to find something on that side of the pond.

Actually yes there is additives. Youjust have to know where to go. Contact a company called Tap Plastics. They even have a good casting resin that has about a 5 minute pot life, and is water thin. You don't need to do any brushing, I cast with this stuff all the time. As long as you pour slowly and in one spot it will spread very nicely and evenly. They call it quikcast. Plus if you use it with their silicone mold material you don't even need mold release(except when creating a 2 part mold, as the silicone will stick together VERY well.

Tips to try.

Coat your moulds with Johnson's baby powder (TALCUM powder). Brush it into all details then brush and shake out all excess. You want a very fine coating with no clumps. Baby powder cuts the surface tension of the rubber allowing the resin to flow into those fine details.

If you have fine longish details that don't fill or trap air. Try making a knife cut through one side of the detail into the mold. Remember that air rises straight up and resin will low into any crack. Most cases the worst you'll have is a fine flash line. This also works well in undercuts trapping air bubbles. Make a cut in the mold to allow a path for the air to escape upward.

Finaly, if your not already using a pressure tank for degassing your rubber and resin during curing. I would suggest getting one. Not all that expensive compaired to resin and rubber and makes casting your own parts easier with better quality and less waste.


I will restore my resin casting album shortly. I do some resin casting now and then. Just getting into making rubber and clear parts but have the casting done by a local shop. For now anyhow.

Joe

http://put.url.here

I'll add some more picture of tools, mould and parts soon.

Joe

This is going to be fun...i'm just gonna sit back and watch the complaints against Joe for showing the "secret formula" to casting on his webshots page.

kevin

Well Kevin, So when does all this fun begin?

Secrets? What secrets? I ain't got no secrets! If I know something it can't be secret. The guys that make and sell resin parts never told me anything. Now those guys have secrets.
Well, a few do anyhow. Some could use some serious secrets. I've been casting my own parts since the late 70s, the hard way, learning as I went. Internet makes it easier now. The answers are mouse clicks away.

Joe

I learned the same way, trial and error, mostly error.. but I eventually got comfortable enough with it to make things pretty consistently. I did a small article on how I pressure cast resin. Might be of some use to you. "Q"
https://armorama.kitmaker.net//features/484

Hi guys,

I've been learning the art of casting much the way it sounds like most of you have-- the hard way by trial and error, error, error. One of the products that I found accidentally was a resin called Siltool from www.silpak.com (I've no connection with them, just a customer). Being in Alaska (not Alabama or wherever my bio says) we're pretty used to limited supply and horrible availability problems for any type of specialty supplies.
After the local (and only) carrier of Alumilite was out of stock for the second month in a row I went looking for alternatives. I found Siltool at a local industrial shop that does a bit of casting. It's a 1:1 two part resin with a 15/20 minute demould time that allows me to "paint" the mould halves first, then fill and get near perfect castings all the time. No pressure vessels, vacuum anythings or special equipment. Yep, and it's cheap even up here in Alaska.
In addition, I've found that by either chilling the mould in the icebox or heating it up in very hot water I can increase or decrease the set time by about 50%. The catalyst's job in the resin mix is to heat the mixture up which in turn helps cure it. By advancing or retarding this temperature you can really effect the set time of the resin.
I rarely have to use this technique because this resin has a great working time, but it's handy knowledge to have.

Jim
Large Scale Armory
Alaska!

Have you tried cooling the resin in a pan of ice water befor mixing?

Joe

Joe,

It has been my experience that trying to change the set time of the resin by heating or cooling the resin chemicals has always proven difficult to do accurately or consistently. After making a bunch of hopeless piles of goo instead of parts I went back to varying the mould temperature as the results were much more predictable. Perhaps others have had better success at this but I found varying mould temperatures worked best for me.
The answer for me was finding the right resin (with a nice long demould time). It has allowed me to get the intricate details and slight undercuts by giving me plenty of time to swab out the mould and work the resin under the lips of the undercuts and into the recesses of the details.
Because of this, I'm no longer put off by creating a part with an undercut or really fine detail because I know I can get good results come casting time.


Jim,
Large Scale Armory