Recipe for red patina on brass & copper

A. Immerse objects in a boiling solution of 6,25 gm copper sulphate and 1,25 gm copper acetate/ 1 lit water. Red colour on copper ... Hope it helps and good luck!

A. Hi, I stumbled on your posting and was wondering if you got any good responses for a red patina applied cold. I specialize in patinas and would be happy to share knowledge if you are still inquiring. Dan Romo - Oakland, California, USA 2002 ---- Ed. note: Thanks Dan! Readers with the same needs as Abir view this thread every day; if you're willing to share knowledge, please simply offer a quick tip. Thanks :-)

A. You can try this recipe (for brass)!
200 gm copper carbonate ⇦this on eBay or Amazon [affil links]
100 gm sodium hydroxide [affil links]
1 lit water
Cold immersion! Golden yellow-orange-dark red Pranam!

Red patina for copper:
100 gm potassium ferrocyanide ⇦this on eBay or Amazon [affil links]
1 lit water

A. Try Hughes/Rowe book "The Colouring, Bronzing & Patination of Metals" [on eBay, Amazon, AbeBooks affil links]
--there you can find many other ways how to colour copper or copper alloys red. There is also very good old book on colouring of metals by A.Hiorns at internet archive web site, and download is free! Hope it helps and good luck.

A. The best way to mass color copper, bronze or brass red is to boil it in a mild copper nitrate ⇦this on eBay or Amazon [affil links] solution. do this in a stainless pot or old stainless sink placed over a gas burner, the solution will corrode any other common metal container so must be stainless.

To find copper nitrate ⇦this on eBay or Amazon [affil links] , look at artist supplies as it is a very common Patina chemical used in art foundries. it is a very deep blue crystal not to be confused with copper sulphate a light blue or sky blue crystal.

It is easy to make but requires handling strong nitric acid and will produce a brown vapor that is toxic so not recommended for novices.

The red oxide produced is the reddest I have ever seen on brass or bronze by any other means and the oxide compound is so stable that it does not require waxing to keep the color. varying the time and strength of solution will very the color. Best reds are from weak solutions boiled over a longer time, several hours.

A point to consider when using this process is that when a cold object is placed into the solution and boiled any gas or air trapped in porosity or internal closed cavities will heat up and expand. this part is no problem but if the object is left in the solution to cool down then this air pocket will contract it will pull into it the solution. this solution now inside the metal surface will bleed and cause problems later. the way around this is to always remove the objects from the boiling solution while it is still boiling and wash immediately in clean water. this way as it cools and contracts only clean water will be drawn into any closed cavity in the object.
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The following I only mention for research purposes only as it involves a molten solution hotter than boiling point of water and if any water , wet object is placed in this molten solution. rapid expansion of water to steam, steam being 2000 times the volume of water, will cause an explosion as the steam is generated rapidly at these temperatures. potentials for dangers aside the results are beyond any other color range achievable by any other chemical process, typically for small objects only .
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There is one more method that is used to produce the most amazing range or red yellows and orange colors that cannot be seen in any standard Patina book. and that is to boil the object in a molten salt of potassium nitrate or sodium nitrate ⇦this on Amazon [affil link] or mixtures of both. The dry crystals will melt at around 200 °C. It is done in a cast iron retort. The salts are super oxidizing agents and at molten temperature strange reactions on the surface of copper, brass, iron, bronze, stainless, etc. will occur.

A. I've done a similar red finish on copper and brass using a similar process to a Rokushō patina.

Rokushō patina:

15 g copper acetate [affil links]
15 g copper sulphate
0.5 L solution of white vinegar ⇦in bulk on eBay or Amazon [affil links] diluted 5-12% with water

How I made the ingredients:

Copper acetate can be made by mixing equal parts hydrogen peroxide and distilled white vinegar, boil it for a moment or two then let it cool down a bit, I let mine simmer on low. Throw in some copper, doesn't matter what, just so long as it's copper and reasonably pure, wire, tubing, sheet, whatever, doesn't need a whole lot 20-30 g will do fine. Let it simmer and react, you'll get bubbles and it will slowly turn a blue green color. Keep it on low and it will slowly evaporate leaving you nice copper acetate crystals.

Copper sulphate is much easier to make. Most of your big box home improvement stores will carry copper sulphate as a root killer for septic systems, read the ingredients and you should be able to find it without too much problem.

The following are pictures of my test pieces, the first one is brass and the second is copper.

You can adjust the final coloration by varying temperature, individual chemical concentrations, and the overall concentration of the chemical bath.

Now, for the warning:
All of the chemicals I've used in this have the potential to be toxic and dangerous. Read through the MSDS for all the stuff used to make sure you can keep yourself safe.

A. Hi Miguel. There are two general approaches to coloring copper: chemical patinas and flame coloring.

As a general rule, chemical patinas give you the strong saturated colors, and flame coloring gives you more diffraction coloring of the rainbow/oil slick type. We have many threads here on each approach.

Regards,

A. Hi Bruce. It is possible to patinate brass to a red color, and it probably isn't cost prohibitive. However, this too is a surface finish which can be harmed by your assembly process, or perhaps wear off in use. I would not patinate under paint, as it is difficult enough to get robust adhesion on brass. Good luck.

Regards,

? Good day Bruce.

Given that you are a product designer, I have a silly question.
Does the paint exhibit "elastic" properties when cured?
Just a thought.

Regards,

A. Hi Nick. Any non-exotic metal is at risk of being attacked by this. High temperature glass, like Pyrex, sounds ideal.

Regards,

(To show dark vs. relieved areas)
Courtesy: Balfour.com

A. Hi Chris, I'm no artist but if you look at high school or college rings, you'll never see one where the high spots are dark and the recesses bright -- it's always the reverse, what will tend towards occurring naturally. So you might be able to lightly relieve the high spots of your panels (either the centers OR the edges & corners) back in the direction of coppery/brassy. In fact the pic looks like you have relieved the center.

Luck & Regards,