Questions about acids

[Will W.]

I've read that to bring out the pattern in Damascus, you need to etch it in acid. I know a fair deal about chemistry and acids, and I am weary about working with them (for obvious reasons) but I do want to do pattern welded knives, eventually. I have de-galvanized steel before using vinegar (weak acetic acid), it takes a while but vinegar is far more safe than more potent acids. I realize that zinc is pretty reactive, so even a weak acid can strip it, but is it possible to etch with vinegar? Would I perhaps have to concentrate it? Also, any general information regarding storage and disposal of acids would be very appreciated, I have very little actual experience with them. The only way I know to dispose of it is to neutralize it and call a hazmat team. Thanks in advance. 

[ThomasPowers]

Should be a lot of threads covering this and perhaps mentioning that hot vinegar and salt does well but leave very little topography.  Many makers will use Ferric Chloride as it's less hazardous if you come in contact with your skin but is an aggressive etch.

How are you neutralizing which acid that you need a hazmat team afterwards?

[Will W.]

I tried searching the forum for info on using vinegar, and i couldnt find much. But I know that adding baking soda to most acids neutralizes it. The way i understand it, it lowers the ph to the point where its no longer very acidic. But for obvious reasons, you can't dump it down the drain or anything like that, so the only way I know to get rid of it is have it disposed of by a hazmat team. No doubt, I could be wrong about this, my knowledge is rather limited on the subject. That's interesting about the hot vinegar and salt though. I may try that in the future. 

[SLAG]

Will W.  sir.

Baking soda will work. But the supermarket stuff would be expensive should you wish to neutralize a lot of acid. Limestone is cheaper. And crushed limestone will work faster. Any of the three will neutralize the acid. Be careful do it outside keep yourself away from the reacting chemicals and do not breathe any fumes or vapor. They are corrosive.

The reaction will continue as add the chemical but will eventually stop and the acid is neutralized. The neutralized solution can then be disposed of. (if the acid was muriatic acid or acetic acid (vinegar), or other organic acid (like oxalic acid), it can be disposed in the sewage water. If the acid was a more exotic metal acid (like chromium) evaporation will get rid of the water portion and if you wish to be scrupulous, mix the metallic residue with cement and use the resultant product for paving stones door stops etc.(all right I'm kidding). But why would you be resorting to a chromic or hydrofluoric acid?

A basic chemical like sodium hydroxide (lye) would work even faster but could very well be explosive. So please stay away from using it.

The pH of the solution will rise with the treatment of the neutralizing chemicals mentioned above. Neutral is about 7.0 pH lower than 7.0 is acidic and above 7.0 is basic.

Have fun with it. But please do not put untreated spent acidic etching solution down the toilet. It will chew xxxx out of the pipes.

Hope that helps.

Regards to, Tout La Gangue.

Salut,

SLAG.

[ThomasPowers]

Note that ferric chloride will eat copper, silver and gold as well as iron/steel; it's an oddball as it's mild on flesh. Do NOT dump it in your sewer pipes!

[Will W.]

SLAG, I considered using a base like lye to neutralize as well, but I figured that would cause a more violent reaction, like you describe. I've always been told that there's an abundance of limestone in my area, and I've tried to find it before and test it, with little luck. I think I would just use baking soda, as I would not be neutralizing very often, cost is not a huge deal. I've considered using muriatic acid and ferric chloride though. If I spend the time to make a pattern welded blade, I would want to make it look nice at the end, so from what you say Thomas, vinegar just is not worth it. Ferric chloride comes in a powdered form, and must be pre-mixed to etch, right? How do you safely store the solution once mixed? In closed glass containers I assume? 

[ThomasPowers]

Depends on what you want, I have a blade I finished with hot salt and vinegar that had excellent colour differentiation and has looked great since around 1992.  I don't want topography on an eating or cooking blade for obvious reasons.  It looks GREAT not nice---just no topography.

 

[Will W.]

OK. I understand what you mean. Seems there is no simplistic answer, as is almost always the case. I'll give the vinegar and salt thing a try if I ever make a successful pattern welded blade. Thanks for the input.

[ThomasPowers]

If we all liked the exact same things then either everyone would be a blacksmith or no one would be a blacksmith.