[chillpill]

Hello everyone.  Firstly I apologize if this is somewhat an odd post, for I am not a chemist or enrolled to study chemistry.  What I am is an artist.

I ended up in your graces due to wanting to learn more about rust and the process of rusting - and in particular, if there was any way to affect the color of rust?

I've been experimenting with some rusting techniques that involve steel and hydrogen peroxide.  The end result is a beautiful rust with typical "earthy tones" for coloration.

My question to you all if I may is this:

Is there any way that you know of to affect the color of the rust?  For example, if you wanted blue or green rust - would there be any chemical that could be applied during the rusting process that might achieve such colors?

Thank you in advance for your help - and my apologies if this is way off topic!

Sincerely,

Danno

[Grafter]

Since you arent a chemist, i guess we'll have to keep the explanations to a minimum.

Rust is basically oxidised iron. There is iron in the steel you are using, which provides the rusty tones you are used to. However, if you are willing to expand you horizons somewhat, you may be able to access a wide variety of pigments by oxidising other metals.

If you want rapid rusting, you are going to want to oxidise your metals. Try different oxidising agents, eg KMnO₄ as the impurities added by them will give different tones.

Also, use different metals. If you can oxidise copper, you will get turquoises and blues, nickel will give vivid greens, manganese deep purples, chromium oranges. The colour of transition metal oxides are well documented.

[chillpill]

Wow.  That's really helped a lot already.  I can see some more creative possibilities!

Some questions:

1) Does this KMnO4 have a laymans name? eg. H202 = Hydrogen Peroxide)
2) Do you know offhand of any resources that deal with color of transition metal oxides on the web?

Thank you!

Danno
 

[Borek]

Does this KMnO4 have a laymans name?

I am not sure it sounds like a laymans name:

potassium permanganate

[lemonoman]

According to Fisher Scientific, KMnO₄ can also be called Permanganic acid, potassium salt, or Permanganate of potash...those are really kinda obscure though...

And according to J.T. Baker, they are also known as Condy's crystals...which I personally have never heard.

Also, maybe we should ask...KMnO₄ might be hard for people to get their hands on.  Are there any household-handy oxidising agents?

For example, household bleach (Sodium Hypochlorite) is an oxidising agent...isn't it?  Not nearly as strong...but it's DEFINITELY easier to get.

[chillpill]

Excellent.

Yes that is a good call.  I would need to be easily able to pronounce and purchase these substances.

Are there any other oxidizing agents that could be used?

Currently I have just experimented with hydrogen peroxide which has given nice results but is quite toxic when it vaporizes (I use heat in the artistic process) and is also relatively expensive.

I will be experimenting with the otehr metals mentioned by Grafter.

Thanks everyone so far - I appreciate you all taking the time to share your expertise.

Danno

[hmx9123]

You should be aware of a few things when you're oxidizing:

1. Oxidizing agents come in different strengths.  Potassium permanganate (which can be obtained in the right places commercially) is a very powerful oxidizing agent.  It can easily form explosive compositions with finely divided metals, or possibly spontaneously inginte.  Finely divided metals are reducing agents.  When you mix a strong oxidizing and a strong reducing agent, you usually wind up with a fire or explosion.  Permangantes are known to be unpredictable in nature, especially in the pyro community.  In a lab setting, it's OK.  At home, it's a bit more tricky.  I say this because you specifically said you were not a chemist.

2. Some oxidizing agents (permangantes, dichromates, etc.) have their own color.  Permangantes are a very deep purple, totally water soluble and stain EVERYTHING.  Dichromates are orange, etc.  Chances are, many of the pigments you work with on a daily basis are probably some sort of transition metal oxide or salt.

3. As was stated previsouly, different transition metals will give different colors.  You also need to be careful to choose a color that won't fade.  Some colors are brilliant, but over time in air, they will degrade because the air oxidizes them or what not.

If you're looking for some good greens and blues, you may want to look at ceramic stores for copper salts, specifically copper chloride (either copper I or II) and copper carbonates.  You can even make copper carbonates (azurite and malachite) yourself.  I'm assuming you want a non-water soluble material that is stable to air.  Go to your farm supply store near you (you'll have to drive if you live in the city, or maybe visit a garden shop) and ask for sulfate of copper or copper sulfate.  It's also called bluestone.  You'll get water-soluble blue crystals.  Dissolve them in water and then add a solution of baking soda dissolved in water.  You wind up with light blue solid that is insoluble in water (a mixture of azurite and malachite).  Filter it off, and mix it in with whatever you've got as a paint.

If you want some more suggestions, tell us what colors you're looking for, and we may be able to help.

[woelen]

Excellent.

Yes that is a good call.  I would need to be easily able to pronounce and purchase these substances.

Are there any other oxidizing agents that could be used?

Currently I have just experimented with hydrogen peroxide which has given nice results but is quite toxic when it vaporizes (I use heat in the artistic process) and is also relatively expensive.

I will be experimenting with the otehr metals mentioned by Grafter.

Thanks everyone so far - I appreciate you all taking the time to share your expertise.

Danno

When oxidizing metals, please be aware of the risks.

If I were you, I would not use permanganate. Its reaction products are very dark, almost black or very dark brown under the conditions you are intending to use it. Besides that, permanganate may cause fire or react very violently with greasy products and other organic products. E.g. with glycerin it gives an intense hot purple flame.

Dichromate also is not good in the hands of a non-chemist. It is less reactive than permanganate, but it is way more toxic. Dichromate contains so-called hexavalent chromium and that probably is a carcinogen. It certainly will not kill you on incidental exposure, but if you do not know the risks and do not know how to handle the material safely, then please do not use it.

Oxidizing copper metal to form a green patina can be done with special substances, made for that purpose. You should be able to obtain that material in art and paint shops. Another option may be to make a slurry of very fine white sand, portland cement, dilute hydrochloric acid and a SMALL amount of bleach. Do this OUTSIDE (because some chlorine gas will be formed) and paint this slurry on a copper object. Let it sit on the copper object for a day or two. When the layer has dried and hardened, you may need to scrape off the thicker parts. You'll see that the copper object is covered with a lightgreen layer of 'rust'.

Succes,

Wilco

[chillpill]

Thats great info guys.

Yeah roger that regarding the risks.  The first time I did this rusitng I inhaled some of the H2O2 vapour (since I use heat it oxidizes very fast and produces steam) and I've been gettting headaches almost daily ever since.  I'm not certain if the headaches are from the vapour but it seems weird they started happening around the same time - especially since in my 30 odd years, I've never been one to get headaches.   It's been about 5 months and they aren't going away!

But, my own dumb fault really.   I've purchased a good quality vapour mask from the hardware store and hope that will offer me the protection I need.  

Thanks again to you all for your help.  I am looking forward to experimenting with all this info!

Sincerely,

Danno

[Garneck]

manganese deep purples, chromium oranges. The colour of transition metal oxides are well documented.

Manganese (IV) oxide is brown and chromium (III) oxide is green. You're talking about manganates and chromates.