Guys,

What materials should not be on actions going to be blued in a caustic bluing bath?

Wondering if I can use a brass pin to align a piece that will be silver soldered before bluing.

I vaguely remember that there may be a problem with brass in caustic salts.

Thanks!

Hot bluing salts can be 'killed ' by copper or it's alloys brass, bronze.IIRC aluminum will be destroyed. Basically then it's steel only in the salts.

Carbon steel only! Not only will other materials kill the salts, that's the small problem, they usually erupt showering the worker with 300' bad stuff which usually leads to an extended vacation in the hospital.

Thanks Guy! I'll refrain from the brass pin. Damn glad I checked. The guy doing the bluing would NOT have been pleased with me.

It also advisable to were protection goggles when working with blueing salts. We stored ours in a 50 gal drum,and it had a bad seal on it,and they do absorb moisture,and these did.I took a coffee can full of salts out to add to the tanks and poured them in,and a big blob went into the tanks and splashed back up in my eyes.That nice hot,solution burnt my eyes so bad,that the doc said i would never see again. Well i,am typing this,so i didn,t loose my eye sight,BUT I was in pain for a long time,and TOTALLY BLIND for one and a half years. So, wear protection people. van

Amen and thank God for you Van. I don't usualy say thing s like that but I'm glad you recovered, I know a guy that didn't.

Don

Van,

Good Grief! Am SOOO glad you're getting better. That is the stuff of nightmares.

I work with salt pots for heat treating. The high temp pot is loaded with 1:1 CaCl2 and NaCl. We run it as hot as 2050F sometimes. That stuff is just terrifying! It is self incandescing and has a viscosity lower than water. It would absolutely crisp you if it splashed. We use shields and nomex and leather and all of that suff ... ant it's still scary!!!!

The low temp pot is charged with Brownell's Nitre bluing salts and we're darned careful with that too.

Plans and pictures of the salt pots are on our web site.

Anything made of aluminum will do a dissapearing act in caustic blueing salts.

Van,
glad you are seeing again, and thanks for the warning.

I wear a good deal of protective gear when I blue.. long sleeves, heavy apron, FULL face resperator, chemical gloves with nitrile gloves under them, long pants, and leather shoes... I guess I could get rubber shrimper boots too...

basically, most non-gunsmithing solders, pot metal, aluminum, copper, etc etc etc will just be consumed in the vat.. remember, it's nearly 300 degrees, PH near 14, and very reactive.

all that being said, I saw on the AGI video to use ICE to add your water to the bathes.. once I tried it, i never looked back, and only use ice to control the water content.

Mike, the bath should be about 293-295, and do NOT control the temp by adjusting the burners... that is, not fine control... once it's at temp, there's no reason to keep it at "full burn" but 3/4 seems to keep it there.

your bath should go to something below 293, and have a rolling boil.. it will then slowly heat up as the water boils off and the solution becomes "more" super saturated, the temp will climb. You can add water/salts to adjust the temp.

if it goes right to and then starts going past 295, adding ice will drive the temp down, as it adds water, and water boils at a lower temp than the salts.

why ice, someone might ask? heat of fussion is the techincal answer... when you add liquid water, it is already "reactive", but when you add ice, the tanks have to melt the ICE to water before hand.

anyway, saw it on the agi video, and solved a problem for me.

jeffe

Great advice Jeffe. Never thought of the ice thing but makes sense.

I've always controlled temp by satuation and leave the burners for a rolling boil. This usually gives me time for any final prep work that needs to be done on the pieces.