13 replies to this topic

[overflow]

I had the idea to oxidize a lock, for decorative purposes (-> change its color), but i don't know from where to start.

AFAIK locks are made of brass and steel, so i'd guess i'd need different oxidizers.

I tried a sodium hypochlorite solution (bleach) for some minutes, but it didn't seem to do anything at all.
I have some potassium nitrate, so i might try a solution of that too.

Does anybody know something more on the subject? (time of the reaction, which oxidizer...)

[YT2095]

don`t you mean Etched rather than oxidised?

anyway, for Brass I`d use Nitric acid or Ferric chloride, but of course you`ll need a template to protect the areas you Don`t want etched.
PCB stencils or photo etching would be a nice way to do it.

[MMMMMM Pyro]

I would probably be more inclined to go the conc. Sulphuric Acid route to be frank.

I dunno, but the thought of using conc. HNO3 just brings up memories of volumnous NOx clouds!

Maybe dilute HNO3 actually...

Hmmm, about the FeCl3, I couldn't really comment, I know swordsmiths use it for etching blades...

[YT2095]

Sulphuric acid is very Slow to attack copper but May attack the Zinc part, I expect it would become quite passive and cease reacting after a short time, Conc nitric would be a waste and wouldn`t react Any faster than dilute.

[pyrotrev]

In my experience a lot of acids will attack the zinc in brass even when reasonably dilute, leaving a copper finish. There are proprietary chemical finishes for brass that leave black/brown/grey finishes.

[Arthur Brown]

I'd be tempted to consider flaming the lock! but there are probably rubber seals or flammable oils. So how about a tinted lacquer misted on from a spray or air brush.

[seymour]

Conc nitric would be a waste and wouldn`t react Any faster than dilute.

Really?

I put a lock in 70% nitric and with much bubbling and nitrogen dioxide emitting the lock corroded fairly significantly. However reducing the size is not the aim, changing the colour is.

A mixture of copper oxide and aluminium stains objects nearby pinky red when ignited.

[FrankRizzo]

Do a Google search for "brass patina".

[overflow]

Thanks everyone, many good suggestions, as always.

@FrankRizzo: I did, and found this excellent resource: Patina formulas

I'd be tempted to consider flaming the lock! but there are probably rubber seals or flammable oils. So how about a tinted lacquer misted on from a spray or air brush.

Flaming sounds like much more fun.

don`t you mean Etched rather than oxidised?

anyway, for Brass I`d use Nitric acid or Ferric chloride, but of course you`ll need a template to protect the areas you Don`t want etched.
PCB stencils or photo etching would be a nice way to do it.

Never knew anything on etching! I do know, and i find it very interesting.

[YT2095]

Really?

I put a lock in 70% nitric and with much bubbling and nitrogen dioxide emitting the lock corroded fairly significantly. However reducing the size is not the aim, changing the colour is.

A mixture of copper oxide and aluminium stains objects nearby pinky red when ignited.

yes really although it`s doubtful if you`d notice with only 70% Nitric, although Nickel metal will hardly react with 70%, take it down to about 25% and it`ll bubble and fizz away quite nicely, Metals can behave Very strangely!

as for the thermit reaction, be Very carful with the exotic ones such as copper oxide and Alu! the Pink stains will be Atomised copper vapor condensing on a cooler surface, nothing Wierd I assure you

[seymour]

And atomised copper vapor condensing onto objects such as limbs is not desirable at all.

Edited by seymour, 22 February 2008 - 02:24 AM.

[YT2095]

Absolutely!
not to mention it`s toxic effects too, esp if inhaled.

I know a fella that did this reaction in school Lab, and used Twice the amount as outlined in the practical, and tried to light this (in the fume hood) but the Mg ribbon didn`t take and kept getting shorter.
rather than get a new length and try again, he kept on using this little stub WOOMPF! knocked him on his ass and burned his hand so badly he`s lost the use of one finger entirely!

16 years old and now has that for the rest of his life

[Arthur Brown]

http://www.tiranti.c...sp?Product=1674

is a product specially made for the job! Yours for £6 +p&p

Tiranti have a nice shop in London and another that I've never visited in the M4 corridor. They have other pyro useful products too. Just keep looking, be polite - artists usually are! They may even acquire potters commodities for you (to use for pyro).

[overflow]

http://www.tiranti.c...sp?Product=1674

is a product specially made for the job! Yours for £6 +p&p

Tiranti have a nice shop in London and another that I've never visited in the M4 corridor. They have other pyro useful products too. Just keep looking, be polite - artists usually are! They may even acquire potters commodities for you (to use for pyro).

Great find!