Q: Finishing Cold Casts

I use automotive swirl remover for the final shine. You CAN get a chrome shine.

A wipe with acetone before you start helps too!

I appreciate the help guys. Looks like I'll continue to tweak the casts and finishes to see what I can get.

I personally like to hit it with 240-400 grit before going straight to the scotch bright, be careful to go one direction and you can get a nice brushed steel look, this method does however totally negate using the method of powdering the mould. However I find that's a patchy way to do it anyway. I find the key is to not be afraid of it, literally just go for it!

Ah, thats good to know. In my head using both methods would give me a uniform look. I was obviously wrong. I think I may have even sanded through the powder coat a little and that gave me patchiness as well. So popular opinion is to stick to one or the other and just buff the hell out of whichever you do? I was fooling myself into thinking this would be simpler. lol

There are many ways to get a metal look on cast parts. What you really need to comprehend is the final finish and purpose. Cold casting is very wasteful and labor intensive while also only working on specific parts or else details are lost or parts brittle. The base material is also a major factor as is the base material color vs the metal finish desired. A black base thats shiny will have a better color on most metal finishes while other metals would require a grey tone. Its all trial and error. But first as stated, you need to comprehend the final result then make a materials list. The base powders sold by the material suppliers have a mesh of 325/425 or so. This is only good for adding to the casting material (ie wasteful and more work) vs a 4000 mesh which is more like super fine dust and flows like water. Its all too much to explain but ive been using metal in molds for many years now and learned by sole trial and error in both materials and powders.

What I will tell you is working with metal powders, wear a respirator and eye protection. NOT a painters dust mask but an actual filtered respirator. That metal once inhaled, is in your lungs to stay unless you end up with a respiratory issue and your lucky enough to have your lungs vacuumed. Then you get to see metal come back out and the look of horror on a doctors face when they think your a Terminator but thats another story.

I dont understand why people are so dedicated and stuck on Smooth On products. Use what works, not whats cheapest. Cheap means nothing when parts fail for whatever reason. Im certain Smooth On has the right product for other uses but I use MPK90:
Casting Resins, cast, resin, hobby* clear resin, hobby, professional, high quality resins
Its the right material for the job, hands down. Its not Onyx or whatever the others are selling but is MPK's own product.

These are NOT cold cast parts but are right from the mold as is, as seen. The base material is MPK90 but the method took me years to perfect. Again this goes back to the right materials for the job. It wasnt till the advent of the MPK90 that the method worked.


Everything here including the grips is raw cast strait from the mold. The gun being cast in parts as well, strait from the mold in color.


These have a black wash, decal letters and a clear coating:


and again showing what the surface looks like after some paint color and a wash being added. The shine holds up,

Beautiful work, Rob. You should sell an e-book detailing your techniques so that others can benefit from your experience.

Thanks,

I forgot to add that no amount of metal will fix an imperfect surface. The initial part to be molded mush have a surface smooth enough for the metal finish to shine on or else all is lost for a smooth reflective surface. Any imperfection will be amplified on the casting. Imperfections can be on the original master, the use of clear coat on the original master, mold release on the original master, silicone poured in a manner that causes a surface imperfection, improperly cured material or silicone and even impropper cleaning of the mold. Having said that, the Sector 7 badges were poured sitting on my front porch.

Id share some techniques but its one of the reasons I get calls for work so it will stay a secret for now. Layering is a whole other process, again no paint what so ever on these parts, strait from the mold as is.
Hero knife in front, castings in rear


some gun grips color layered, right from the mold

Flat out amazing work. I'm fairly certain some of the issues I had with the test batrang were due to imperfections in the cast, just as you mentioned. Until casting it I hadn't realized just how much every ding and dent would show. As far as Smooth On goes I was simply ordering from them already. Though I wouldn't call their prices or their materials cheap. lol Thanks for the advice. Hopefully I'll improve my methods in the coming weeks.

I didnt mean to insinuate Smooth On products being cheap but that fact many will use whatever is cheapest on a project regardless of how wrong the material may be for the job at hand. For cold casting some will push polyester resin as the proper material. Pending the part in question it may well be the proper material but again it gos back to a case by case basis. The less detail and smooth the surface, the more variety of materials can be used. Matsuo has his own method of metallic parts as well. Here is one of his shottys I have. Notice the shell ejector port, thats a casting but even up close, eyeballs to the surface, gun guys cant believe its a casting;


This was a project where a coin needed to melt on que so I made them out of silver base crayons with some metal powder in the pour. The shiny silver one is a plastic casting strait from the mold, to the right those are crayon, the original is to the left. These were test casts, the final ones matched the original all around. Again, crayons.

Great looking stuff man. The bad part about smooth ons powders is they didnt really detail the mesh size online. That or I missed it completely. What I ended up with was a -200 aluminum powder. It seems as fine as talcum to me but I'm sure thats not fine enough for the type of results you're getting. I think I'll try another piece tonight and see what I get this time out.

no doubt the powders Smooth On sells are 325 or 425 mesh. It seems those are standard to materials vendors.

-200 is whats labeled on the jar they sent. whether that helps or hurts I'm not entirely sure.

200? Really? Thats more of a gun powder clump than a fine powder.

I'm afraid so. Possibly even another reason I'm having trouble with the finish. What I have now may just go onto the marketplace. As you said previously, I need something far better than this.

Just keep in mind as mentioned, metal powder once its in the lungs, it stays in the lungs. The finer the mesh, the better the respirator.

I have a dual cartridge respirator meant for air purification. Definitely don't want that powdery stuff in your lungs.

@robstyle - Is there an online supplier you'd recommend that sells the higher mesh value powders?