Substitute for West Systems 423 Graphite Powder?

[soholingo]

I can't find this stuff locally. Is there something else I can use to darken and strengthen the surface coat of a mold?

[davidfee]

If you use mail order, it will be on your front porch in less than a week.

There are gel colorants available at Home Depot, but they are not very opaque and I would not use them on a surface coat for a mold, as I don't think they will give a very hard surface. They are made to work with either epoxy or polyester, which sounds fishy to me.

-David

[chlee]

Have you tried an art supply store? I found some in the aisle with various charcoals and pencils.

- Chung

[Bayport_Bob]

Toner powder (aka carbon powder) for Laser printers is a possibility if you have access to a cartridge. Try it in a test batch and see if the properties are what you're looking for.

Just my opinion & everybody's got one - Bob

[davidfee]

Toner from laser printers and copiers is not carbon alone. It also contains plastic (usually polypropylene, IIRC). The plastic melts and bonds the toner to the paper when it goes through the fuser section. If what you want is to make it black, then this will work. However, the physical properties will be different from pure carbon powder.

I've spent years looking for "substitutes" and I can tell you that the real thing usually works much better. Save yourself the grief and just get a tin of graphite powder here: https://www.cstsales.com/Epoxy_&_Molding/west_system_fillers_and_additives.htm

The 6oz tin has lasted me ~5 years and it's still half full. It cost a measly $7.

Now, if you want metal-filled epoxy, CST also has aluminum powder. Or you can use the steel powder which is used as the fuser cleaner in the large Xerox copiers. That you have to clean with solvent though before you can use it. Again, the "real thing" is so much more convenient.

-David

[soholingo]

I want the hardest blackest molds. Should I do a layer of graphite powder/epoxy, let it dry, and then use a layer of aluminum/epoxy or should I mix graphite and aluminum powders and then use that in the epoxy.

J

[davidfee]

No, they really serve different purposes. The graphite makes the surface hard, yet polishable (and dark). Aluminum (or steel) makes the surface tough and provides good thermal properties (heat transfer).

The aluminum-filled epoxy would be used along the mold flanges and into the corners around the seam. One or two coats of that will be sufficient. When that has become tacky, then apply two coats of the graphite-filled surface resin (allow to tack between coats) to the rest of the mold surface, where the parts will actually be formed.

The aluminum-filled epoxy will give you very tough seams (resistant to chipping) and the graphite-filled epoxy will give you a surface which can be polished if needed.

In my experience, I've used the graphite (black) surface coat for everything and only when there were air bubbles in the seam corners did they chip. So, I think avoiding air bubbles in the surface coat is more important than using different types of surface coat.

You don't need to back-up the graphite surface coat with aluminum-filled epoxy unless your entire mold is going to be metal-filled epoxy. This would be heavy and expensive for anything bigger than a spinner or servo cover.

-David