Cold Cast Resin with metal powder HOW TO question

I am trying to cold cast an item that is about the size of a silver dollar coin. It is a charm that is going to be brass color.

My question is what is the best way to get the brass metallic powder to show through the surface of the charm? The surface is going to be very bumpy with a sculpted image so I know using steel wool will only bring out the surface brass on the raised parts.

Is it better to add a thick paste of resin / brass powder to the mold first, let it cure, than add colored resin on the back (like on Smooth On's website video for the large bronze piece they made) or completely mix the brass powder into the resin and pour into the mold?

The second method for me is not working too well for another piece I am cold casting because the metal powder doesn't stay even in the resin when mixed and poured AND just when I think the resin is at the top of the mold it dries over the edge....some sort of expansion going on.

Other techniques I have seen done with Sculpey clay is to put the powder directly into the mold and press the clay into the mold. Can this be done with cold casting too? Sprinkle the metallic powder into your mold to ensure that it is in all the nooks and crannies. Next pour your resin into the mold.

The other strange thing is that the metallic brass powder makes the piece come out pukie green rather than true brass color.

Sorry so long and so many questions but I am a "cold casting noob!" But getting really good at mold creations!!!

if you are using smooth on products, check out their cast magic powders. not cold cast per se, but very cool.

This is a helmet I made out of Smoothcast 65D (formerly Smoothcast ROTO). I used some of the So-Strong black tint in the resin, and Cast Magic silver:



The Jango on the right is rub & buff. The one on the left is cast magic.



Not as shiny, but still nice, and that required no buffing.

You just dust the mold with the cast magic powder before casting. It fuses to the resin as it cures.

They have a graph on the smooth-on site that shows the cast magic powder colors and what they look like over different tints of resin. I'm guessing that a little red and brown pigment behind a gold powder would get you a good look.

I get the metal powder (it's very fine stuff, like talcum powder) and dust it into the mold. Tap out the excess (save it, it's expensive!)
Then, pour the resin in.
The top layer will be that beautiful metal finish (because it IS a metal finish!)
I have had very little luck with mixing in the powder into the resin and then buffiong it out.
It seems to me that in order to get enough metal into the resin to buff out, you hav e more metal powder than resin in the mi, which may be weaker.
I have only used silpak products though and I do not do this for a living or anything. I have had great success with the poweder in the mold though.

By the way:
With the aluminum powder, at least: DO NOT BREATHE IN THE DUST!
It's too fine and can permeate into your lung tissue or something really bad.

I get the powder from a paint shop in North Hollywood, so I am not sure where else it is available. It isn't the same stuff they sell with the resin for mixing, though maybe that would work as well?

Here ya are mate!

Photo Gallery: Metal Cold Casting With Urethane Resin

Mixing the very fine metallic powder also seems to cause more air bubbles in the final product regardless of how much stirring and mixing.

Too much mixing causes more bubbles to form as well.

I will have to try the method of adding the powder to the mold than pouring the resin.

My other problem is trying to determine the correct amount to pour into the molds. I tend to have a little bit extra resin/powder curing in the mixing cups. Either use less or I have to make multiple molds.

Thanks for the help so far. Testing tonight!

Fill your mold with water, then pour that in a cup to measure how much you need. better than wasting resin.

Not that it matters but this is what I am going to cast. Brass concho for Jack's baldric.

Master clay item.


Borrowing an image from Mojo wiki:

I used to make some brass copies of coins, and I did it this way.

I powdered the mold with the brass powder.

To give the piece some weight, I also used some brass powder in the resin.

I added the powder to one half of the resin, stirred it well, them let it settle for a minute or 2.

Then I mixed the 2nd part in and poured into the mold.

This waiting time was not enough mixture to separate, but I did get all the bubbles out.

Them, once I de-molded, I polished with steel wool, and in some cases, used Brasso, and was happy with the result.

Hope that helps.

I've tried this, and it's pretty cool. The material's cost are a bit steep, thou:

YouTube - Create Cold Cast Metal Effects Using Smooth-Cast® Resin & Real Bronze Powder

I bought a Predator bio that was casted using this technique, turns out awesome....

As Tempus, I find it best to dust the mold then add powder to part A of the resin only and mix it in well allowing bubbles to rise. Put as much powder as you can in up to the point where it starts to get too 'muddy' this is ok as you'll be adding more liquid in the form of part B to make it more pourable.
Also if its a one piece mold, the brass being heavy will tend to settle toward the face of your design. Poke it with mixing stick to release bubbles.

SAS

With this piece we used Smooth-Cast 325 Colormatch with some black tint and bronze powder.

They have the steps used here:
Photo Gallery: Metal Cold Casting With Urethane Resin



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