Nitre bluing

[IMshooter]

I have some small gun parts I have decided to nitre blue.  I know I can buy the chemical salts from Brownells, and have read up on the process.  Can any of you with experience offer some advice?  Thanks.

[BoarHunter]

The hot blue salts sold by Brownells work great. Far better than the cold blue.It is th way they do in factory. They provide all the explanations. For small parts (hanfgun, long gun action) it is very easy indeed as you do not need big tanks and heating source is not an issue either. You can do it in a kitchen, with proper care of course as these hot salt will eat through your skin !

[gunnut69]

The nitre bluing that IMshooter is talking about uses a bath of pure melted salt(potassium nitrate??) to heat blue the steel.. The bluing salts used by factories use a mix of metalic salts and other corrosive chemicals to create a colored corrosion of sorts on the metal.. It is indeed very base and destroys flesh and most material much as would lye.. The nitre bluing salt sold by Brownells actually blues by heat. The advantage of the salt bath is that the results can be seen as it transpires with the part in the transparent molten salt.. The process can also be accomplish with an open flame, as in a torch, or in a lead bath. The problem with both being control.. It is most often used for small parts, screws and pins,.,

[IMshooter]

Sodium nitrate is the salt used.  I worked several years in a contaminants research lab and know exactly what the term "strong oxidizer" means.  My intention is to do this on my concrete driveway using an all metal welding table, Coleman camp stove, lead melting pot, and proper PPE (personal protective equipment).  I have a thermometer and fully intend to stand upwind!  The small parts being colored are from a C-96 Broomhandle.  The rest of the gun is recieving a rust blue job.   I made the grips out of desert ironwood.  Thanks for your replies.

[gunnut69]

The material in a nitre bluing solution is not that dangerous...although at working tempurature (about 600 degrees) they are indeed very hot.. The material BoarHunter was speaking of is a completely different stuff(Oxynate No. 7). It is indeed corrosive.. and operates at a considerabley lower temp than nitre blue. Do NOT blue any heat treated parts in a nitre blueing bath as the temperature may alter the parts temper. Also the fire blue produced by nitre bluing is not as durable as chemical bluing.. The other important thing to remember that nitre salts are as hot as a lead bath and if any moisture is introduced beneath the surface a steam explosion will result. The salts can produce devestating burns as they are thrown from the pot by the steam. I preheat parts to dry them if of a compound nature. A full fave shield and heat protective gear is a good idea..

[BoarHunter]

Oxynate is indeed a mix a caustic soda and potassium nitrate (nitre, so my confusion) plus a few other things, it works at 135 C.

Pure nitre works indeed at a far higher temp around 350C , that will affect tempered steel and soft solder. I have used it in the past for small non ciritcal parts (eg. screws) and it gives more a blue color than black.

In any case you have to use caution.

Properly stored in an air tight container these salts last a very long time.