Cold Casting

[cunningham]

Hello
I need some expertise on the subject of cold casting as my attempts have been lackluster, literally!
The technique seems pretty cut and dry really, but things are not turning out looking as metallic looking as they should, compared to some examples I have seen. All of the information on the web makes the process look straight forward - you mix your resin and the powdered metal at 1/3 part A, 1/3 part B, 1/3 metal powder, stir thoroughly and pour, backfill, and then pull the cast. In almost all of my attempts, the pulled cast comes out in a dull grey, which is normal. After scouring with either sandpaper or steel wool, from course to increasingly fine, my cast doesn't make it to that brilliant shine that I see in all the examples I have seen.
I have used Smooth-On 325 color match, mixed with a little black pigment or none at all, and I have used Onyx fast, both of which have hard shore properties. I have tried with rough sandpaper to take off the outer surface and expose the powder, and made my down to 1000 grit. Same with steel wools. Also I have tried mineral spirits, but all of these are not working out for me. Now I know it has to be me, and not the products, but I can't seem to figure out what I am missing. I have tried more and less powdered metal with no better results.
Can someone tell me what I can try or hopefully what I am missing? Am I not using optimal materials? My aluminum powder is a 200 mesh from Smooth ON.
The picture is of my helmet, on the left compared to a beautiful looking example that I am trying to achieve on the right.
Thanks.

 

[CFT]

Have you tried polishing with some metal polish too? I used steel wool and wet sanding followed by Meguiars chrome polish on a Jango helmet and armor a few years back, and was able to get good results. I did not cast any of these, but the helmet and armor were from different people. The armor took a lot longer to polish to look like the helmet, but the Meguiars is what did the trick.

 

[cunningham]

Have you tried polishing with some metal polish too? I used steel wool and wet sanding followed by Meguiars chrome polish on a Jango helmet and armor a few years back, and was able to get good results. I did not cast any of these, but the helmet and armor were from different people. The armor took a lot longer to polish to look like the helmet, but the Meguiars is what did the trick.

Hi CFT,
No I haven't tried that stuff, but it does sound promising - I'll see if I can find some, thanks!

 

[13doctorwho]

Did you coat the mold with a layer of metal powder before pouring your resin? A lot of what I've read recommends that.

 

[ChickenHaunt]

I did several tests in cold casting, and never got decent results from mixing the powder into the resin. I coat the surface of the mold with powder and back with resin. Polish gently with steel wool. Works great.

Some people do the powder on the surface and also mix it in the resin as a backup, but I prefer to not thicken the resin, as it's going to flow better into the detail at a lower viscosity.

A couple examples of mine:
Artifacts of the Universal Monsters
My Own Maltese Falcon

 

[cunningham]

Thanks for the last 2 replies, as they recommend the same method, I'll reply to both at the same time!
I haven't tried that method on anything large or that required too much clean up as the layer would be so thin I would be afraid to remove it with the excessive sanding. However, the helmet iI want to do is clean and requires no clean up, so I am going to give this a try tonight, thanks again. ChickenHaunt, those artifacts and the falcon look incredible, I hope to get that level of shine!

 

[robstyle]

Being honest, the typical cold casting method is not really necessary. Its material cost and usage can be cut by simply sourcing a higher mesh metal powder and polishing it out inside the mould. Most casting metal powders will be 325 to 425 mesh. I use metal powder in the 10k mesh range. It flows like water and a proper respirator must be used with it. Its not difficult to source if you look at industrial lubricants. The base casting material color will effect the color which is why for metal finish youll want black casting material.

 

[dharma]

To add a bit over the powdering the mold with a god quality metal powder I would recommend you a translucent or clear resin. If not the whitish of the resin will come. It is tr that over the powdered mold type of pieces is not easy to sand, so the better the object you mold the better the surface.
You can always mix a bit of the powder with a varnish and spray few layers over the final piece too.
If you want to make a helmet why not try to make a good paint job instead a metal cast? I mean paint the objet in a very good shinny black and cover with a metal paint lightly, the result use to be very good