Etching with iron(III)chloride hexahydrate

[Ferguson]

I have etched a lot of blades, but I'm no expert. My method is in this thread.

Etching

I have read that doing the first neutralization with vinegar converts some chloride ions to a non corrosive form. (I'm no chemist) I then rinse and neutralize with ammonia, then with a slurry of sodium bicarbonate.
I've never had any corrosion or rusting issues doing it this way.

Good luck sir!

[blue lander]

How polished should a blade be before you etch it? Does it need a mirror finish?

If you etch a blade that's been cleaned and not polished and no pattern emerges (steel just turns uniformly gray) is it possible that you'd get a pattern if you put a mirror finish on the steel and tried again? Or would you at least see some evidence even without the polishing?

[kai]

How polished should a blade be before you etch it? Does it need a mirror finish?

No polish needed per se - it's a matter of taste or what the traditional approach would be for a given culture/piece.

If you etch a blade that's been cleaned and not polished and no pattern emerges (steel just turns uniformly gray) is it possible that you'd get a pattern if you put a mirror finish on the steel and tried again?

Quite rare but possible: If a blade has been polished with power tools the laminations at the surface may be obscured. If accumulating surface rust has not eaten through this "smear" layer the laminations may still not visible. Repeated etching and polishing (by hand) may help to expose any laminations though.

Regards,
Kai

[Jens Nordlunde]

As it has been mentioned, FeCl3 is very agressive, so you have to be careful.
Some time ago this was discussed, and some suggested anything from pineapple juce to lime juice.
I find that ferrycloride is very good, but maybe you should try it on a blade of less value, so you know what happens, as you can always remove it, but just to make sure you know how it works.
Make sure you have the neutralisers at hand before you start.
You may end up with a blade slightly yellowish, but this can be removed by adding acid free oil and work the blade over with very fine steel wool - very gently.
Good luck
Jens

[kai]

Hello Steve,

Yes, your etching results are certainly fun - keep them coming!

I have read that doing the first neutralization with vinegar converts some chloride ions to a non corrosive form.

No, chloride ions will need to be extensively rinsed off regardless of any intermediate treatment.

The vinegar may help to remove excess iron salts (if you leave it on for too long you'll reduce the contrast of the stain though) and, thus, avoid the yellowish color which is often visible in blades treated with ferric chloride.

I then rinse and neutralize with ammonia, then with a slurry of sodium bicarbonate.

I'm not convinced it is really necessary to do both. Ammonia may have advantages in reaching crevices in pitted/cracked blades but you'll need to rinse such blades extremely carefully anyway. Ammonia chloride residues are moderately acidic while sodium chloride is neutral; this is pretty academic though since you need to work with excess ammonia or sodium bicarbonate, anyway, and both solutions are alkaline.

Once you have neutralized any traces of acid, you really need to rinse away any salts/ions. Deionized water, lots of DI water!

Regards,
Kai