Brass Patina Recipe?

[Mal Paso]

I'm not looking for corrosion and have avoided chemicals that might produce that porous green finish or pitting of any kind. A couple household chemical recipes I tried produced green on cartridge brass. I'm looking the kind of brown oxide that protects old statues.

I suspect many molds have naturally oxidized past the point of tinning. I should have heat cycled my molds with blocks open before the first cast but I was overly careful. I really should have more molds too. That #503 has cast almost a half ton of lead.

[JonB_in_Glencoe]

I was going to wait til I got out and did some BP shooting to try using cleaning water as suggested by another member. BUT, what about just using black powder right from the can, disolved into water in a crockpot...non-metalic and provides heat. How much do you think ? 100 grains per half gallon of water ? or more ?
Jon

PS, why would you avoid soaking the allignment pins ?

[Mal Paso]

I was going to wait til I got out and did some BP shooting to try using cleaning water as suggested by another member. BUT, what about just using black powder right from the can, disolved into water in a crockpot...non-metalic and provides heat. How much do you think ? 100 grains per half gallon of water ? or more ?
Jon

PS, why would you avoid soaking the allignment pins ?

I have no idea how BP would work. Liver of Sulfur is easily available, not expensive, and has known results. I would experiment on scrap brass before trying it on a fine mold. Crockpot sounds like a good idea.

Pins? Liver of Sulfur also oxidizes Steel and I wanted to minimize that.

Longbow never had these problems and it may be that he was running his mold cooler. I started out running hotter Alloy and a cooler mold but I'm now casting at 680F. That's just enough to consistently get sharp edges on the bands. 3+ pours per minute.

Fascinating!

[Jailer]

What about a mix of vinegar and hydrogen peroxide?

http://brewingrabble.com/resources/surface-lead.htm

[ctious]

What about a mix of vinegar and hydrogen peroxide?

http://brewingrabble.com/resources/surface-lead.htm

That sounds like its more to clean the lead off the surface. Does not sound like it creates a protectivecoating

[longbow]

I run lead and mould hot with brass moulds. Hot being a relative term because I cast "by eye" ~ I have never used a thermometer. I usually pre-heat the mould until mould lube smokes a bit and I heat the lead until I get a slight golden tint on the surface then start casting.

I cast fast and steady until the sprue puddle takes too long to solidify then turn the heat down a little. So basically, I have the mould almost to melt temperature for a bit then turn the heat down so that the sprue puddle hardens in a few seconds after casting.

I have had several moulds beyond the melt temperature by over doing the preheat accidentally ~ not brass moulds so far but some home made moulds with brass nose forms.

Personally, I think that the preheating I do starts a bit of an oxide layer on the surface.

Also, I think anything that causes a patina is corroding the surface, maybe just a bit but after all bluing of steel is a corrosion process. What you don't want to do is get a solution that is too aggressive or selective. Brass has zinc and copper in it so some solutions can be selective and leach one or the other from the surface.

Not criticizing what you are doing, I understand that, but some reading this may decide to try something that is too aggressive and ruin a mould.

Longbow

[Jailer]

That sounds like its more to clean the lead off the surface. Does not sound like it creates a protective coating

I dunno, they say a picture is worth a thousand words.......

[Mal Paso]

Nice Tan! Much more even than mine.

[JonB_in_Glencoe]

Mal,
I'm thinking the Clean side is the side treated with the vinegar/hydrogen peroxide mix...not the patina'ed half. I am assuming the patina was from actual aging.

you can see the lead spots on the top of the "brown" mold half.
The Clean side has no lead spots on the top of the mold block and the actual aged patina is removed.

Correct me if I'm wrong Jailer.

The article by Brewer John Palmer (I've read his book about brewing, he has a Engineering/metalurgy Major) A very smart dude. Read the linked article, it explains
that the solution removes lead smeared onto the brass from the machining process and
brewers who use newly manufactured brass fitting would rather not have lead exposed to the wort/Beer.

[geargnasher]

A citric acid solution will passivate the surface and leave a very light patina.

Gear

[JonB_in_Glencoe]

Gear,
I did think of that. Do you think that "very light patina"/passivate would be enough to stop the tinning I got, as shown in the photo I previously posted ?
Jon

[Jailer]

Mal,
I'm thinking the Clean side is the side treated with the vinegar/hydrogen peroxide mix...not the patina'ed half. I am assuming the patina was from actual aging.

you can see the lead spots on the top of the "brown" mold half.
The Clean side has no lead spots on the top of the mold block and the actual aged patina is removed.

Correct me if I'm wrong Jailer.

The article by Brewer John Palmer (I've read his book about brewing, he has a Engineering/metalurgy Major) A very smart dude. Read the linked article, it explains
that the solution removes lead smeared onto the brass from the machining process and
brewers who use newly manufactured brass fitting would rather not have lead exposed to the wort/Beer.

The brown side is the side that was soaked. It started as a lead removal experiment that didn't work. The lead that was stuck on the mold didn't come off.

It was a dull golden color for a short time after it soaked and then eventually turned the darker brown that it is now.

[MakeMineA10mm]

Tagged for future referrence

[Dannix]

I'd like to thank everyone for this thread. I have tinning on a Miha 9mm brass mould, and this thread could not have come at a better time.

[Dannix]

I would be willing to pay extra but it might be a complication he doesn't need.

Yeah, that's likely true, but I would be willing to pay extra too.

Did you use all 4 ounces of Liver of Sulfur on this one mould? I have a mould tinned like JonB_in_Glencoe's, so I'm going to try to make patinaing a near future weekend's project.

I'm seeing "116 B-12 CHEMTOOL Carburetor/Cho​ke Cleaner" at $50. Is there any other, cheaper, "zero residue cleaner" option?

Also, to be clear, you left your sprue plate et al attached when you did this, but tried to avoid exposure for the alignment ? I ask because the sprue plate and stop seem patinaed as well.

Did you ever get in touch with your old sculpture caster friend?

[Dannix]

Nice results.

How long did you let it sit in the vinegar/hydrogen peroxide mix? At what temperature?

I presume you used a 2-to-1 ratio of 5% Acetic Acid (White Distilled
Vinegar) and 3% Hydrogen Peroxide, as discussed on the thread you linked?

I dunno, they say a picture is worth a thousand words.......

[williamwaco]

Patina:

I have used a propane torch to achieve this with recalcitrant iron and aluminum molds. (Never owned a brass mold - soon now. )

I use it only after all else fails but I have had good results with it.

.


.

[Mal Paso]

The brown side is the side that was soaked. It started as a lead removal experiment that didn't work. The lead that was stuck on the mold didn't come off.

It was a dull golden color for a short time after it soaked and then eventually turned the darker brown that it is now.

Have you cast with the mold yet? I cleaned up my 640 last night. The Alloy was mostly sintered to the brass and not fully bonded so easier to clean than the 503.

I think any removal of lead is going to be surface molecules and if the lead can be seen it's too thick to be dissolved by such a mild solution. If the visible lead is removed the solution may remove the microscopic lead that would impede the formation of oxide. Very Cool!

I knew I wanted the 432640 to be more oxidized before the first cast but wasn't sure about heat cycling with blocks open, didn't know how to patina, and Just Couldn't Wait. Need More Molds, More Calibers, More Patience!

[Jailer]

Nice results.

How long did you let it sit in the vinegar/hydrogen peroxide mix? At what temperature?

I presume you used a 2-to-1 ratio of 5% Acetic Acid (White Distilled
Vinegar) and 3% Hydrogen Peroxide, as discussed on the thread you linked?

Not long, maybe 5 minutes or so. It's been a while ago and I can't remember exactly how long I soaked it. The mixture was exactly as described in the link I posted.

Have you cast with the mold yet? I cleaned up my 640 last night. The Alloy was mostly sintered to the brass and not fully bonded so easier to clean than the 503.

I think any removal of lead is going to be surface molecules and if the lead can be seen it's too thick to be dissolved by such a mild solution. If the visible lead is removed the solution may remove the microscopic lead that would impede the formation of oxide. Very Cool!

I knew I wanted the 432640 to be more oxidized before the first cast but wasn't sure about heat cycling with blocks open, didn't know how to patina, and Just Couldn't Wait. Need More Molds, More Calibers, More Patience!

That mold is a mess. It was my first hollow point mold and one of the first molds I purchased when I started casting. Of course ignorance is bliss and I didn't set the mold up properly and I made an absolute mess of it. I still need to take it apart and clean it well and set it up properly. It does cast nicely and makes great bullets but needs some attention before I use it again.

[Reverend Recoil]

Ammonia will react will copper alloys to produce a finish from dull yellow, to a brown color, and to eventually a heavy crusty green coating. Artist looking for patina compounds that duplicate centuries of the aging of bronze sculpture may use something like liver of sulfur. I think liver of sulfur is ammonium sulfate. Ammonium sulfate is used to age the patina of new copper roof and gutter repairs to match the appearance of the original work. All us bullet casters need is a simple chemical that will passivate the surface of a brass mold so the molten lead will not wet( or tin) the surface. Any solution with ammonia will work such as ammonia based home cleaners or copper removing bore solvent. Do not soak the mold block in the ammonia or it will be spoiled by a thick green corrosive crust. Wipe the mold with a strong ammonia solution several times over a day or so until you get a dark brown patina.