hot blue solution

savarin

savarin

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I have found a recipe for a hot blue solution as follows
1.13Kg Sodium Hydroxide
0.56Kg Sodium Nitrate
1.6L water
heat to 124-130 'C
What would be a suitable container to use to boil the mix?
tin can, stainless container etc???
 
After consulting two different gunsmithing books, the preferred material for tanks is stainless. Hot rolled steel will also work. Joints must be welded, not soldered or brazed. It should be only large enough to handle the largest part to be blued. It should be insulated for ease of temperature control.
 
Thanks.
Any other tips I should consider as I've never done it before.
 
Many years ago while still in HS, I worked at a machine shop that produced clone Sunnen honing machines. They had a black oxide area for parts that required this process (messy and hot). They ran mild steel troughs tanks and suspended the parts in the heated solution. They also aerated the solution with low pressure air to keep the solution suspended/mixed. I remember the parts looked extremely nice especially if it started out with a polished finish. I later worked at second machine shop that specialized in hydraulic cylinder repair and machining. They too used shop air to aerate the chromium solution (deep vertical tanks).
 
Roy F. Dunlap's book 'Gunsmithing', has a chapter on Browning, Blueing and Blacking of Metal. Roughly 40 pages on the subject.

'Professional Gunsmithing' by Walter Howe has a section 'Blueing Tank Materials and Construction, pp392-396. It also has a section on the 'Hot Rusting Process', pp414-423.

After once considering the possibility of getting equipped for hot blueing I concluded that I would stay with cold blueing. Hot blueing seemed to only be worthwhile when used regularly by professionals who have enough business to justify it. Hopefully some other members here have some personal experience with hot blueing and can offer some practical tips for you.
 
savarin said:
I have found a recipe for a hot blue solution as follows
1.13Kg Sodium Hydroxide
0.56Kg Sodium Nitrate
1.6L water
heat to 124-130 'C
What would be a suitable container to use to boil the mix?
tin can, stainless container etc???
Click to expand...
Watch out, corrosive (and potentially dangerous) stuff. Keep it well away from anything you care about, during both storage and use.
 
Use in a well ventilated area. Use PPE, full face mask, respirator,etc. Sodium hydroxide will eat flesh, literally. Mist created during boiling will attack lung tissue. If you get any spray on your skin, wash immediately with cold water and it wouldn't hurt to use some vinegar to neutralize the caustic.
 
I have been doing a similar recipe for years. And yes, it’s nasty stuff, but the results are excellent. I would do it outside and stand up wind. Put a fire extinguisher next to you. And a very large bucket/drum of fresh water next you in case you need to wash yourself off. I use a stainless vessel. Takes about 20 min for the part(s) to turn a nice black. The water will boil off, you will need to add water, BE CAREFUL when doing this. For some season I have not been very successful in reusing the solution for the next time? I make a fresh batch every time. Please be safe…Dave
 
Dave, considering just how nasty this stuff is, may I ask how one disposes of it in a proper manner?
 
well, sodium hydroxide is drain cleaner so that should give a clue,
Sodium Nitrate is used as a preservative in bacon and hot dogs. Its also found in a lot of plant products especially spinich so again should not be a problem.
Mind you from what I gather it may be a different problem altogether in California.:laughing:
 
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