doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Oscar's niter blue

I originally used about 10% Manganese Dioxide in my mix but it went bad last year. I don't know what happen, as it started to melt a bunch of black foam kept raising to the surface. When it was all melted I poured it out. my new batch is from Brownell's. it seems to work fine. As far as I know there is no MD in the Brownell's. I have a large pot and small one I made from a iron 2" end cap that I removed the threads from. I use it for small parts like pins and screws so the small pot is very handy.

Brownells Niter Blue salts are NOT nitre blueing salts per Oscar. He was strongly against them! Strange my notes show aluminum sulfate. I can tell you it works very well and the coloring begins when the salts melt. Time seems to be the biggest factor.
bill

Whatever they sell at Brownell's I have used it for both coloring and heat drawing for heat-treating parts. When I bought potassium nitrate at the drug store it was white and the stuff from Brownell's is reddish, that's the only difference that I know of. It works great for me.

Nice work Doug

Thank you Harry.

Are you doing any B & W yet??

I have used Brownells niter salts and have used potassium nitrate, both with good results. I too noticed the difference in color and decided to call Brownells. One of their tech guys told me that the only reason they are pink is so that you dont get the niter blue salts mixed up with their regular hot blue salts. As far as it chemical makeup of their niter blue salts, he did not know.

I'll cast another vote for the Brownell's salts. They have worked fine for me for years. Just follow their directions. As to the "dislike" of things Brownells by Dr. Gaddy, I spoke with both parties about their ongoing small dispute. Dr. Gaddy essentially did not like anything about Brownells from top to bottom. He as much as said so. Apparently there was an old dispute between them. The folks at Brownells (now this was a number of years ago, before Dr. Gaddy passed) were quite aware of the difference of opinion, but would not discuss it.

At that time, as well as now, I was of the opinion tht Brownells took "the high road" when asked about the dispute. At any rate, their nitre salts are a good product when used according to the directions. The pink stuff is a coloring agent so you can keep nitre sales apart from other salts.

Channing,
was there any difference in the color of the finished parts?

I like the blueness of Doug's trigger bow above better than the black colors that I have seen in some cases. I understand that temperature affects this but is that all?

Angier page 123 H 2
""At Springfield armory a mixture of Saltpeter (Potassium Nitrate) and 8 to 10% manganese peroxide is thorughly mixed & heated to about 200°C (390°F), at which temperature a pinch of sawdust dropped onto it briskly burns off. The degreeased parts are stirred about in it for 5 minutes or until the desired color is obtained, freed from adherent saltpeter with hot water, darkened in hot whale oil, cleaned with gasoline and finally oiled.
According to Hartmann, a temperature of 315°C (600°F), that is about the melting popint of saltpeter, is necessary for producing a deep blue colour: the same author (and many others) state that the addition of manganese peroxide is of no special advantage, safe a slight quickening of the process.""

The only times I ever tried it I simply used straight saltpeter & immeresed the parts as soon as it melted & was quite pleased with the results. No doubt results (Color) can be varied some by the exact temp used. Also I have no idea what the difference in effect would be between using the Manganese Peroxide Angier mentions & the Mangenese Dioxide Oscar used would be.

I recently experimented a bit with Brownells Nitre Blue salts. I added manganese dioxide per Oscar's formula. Starting at about 600°, I immersed well polished steel samples until color change was complete, usually 10-15 min. I ran samples until I got to about 850°. I found that 750° was hot enough to do a good job with full color development in about 10 min. with my particular samples(shotgun barrel sections) I could see the double color change as the oxide film grew thicker. Final color was a rich blue approaching black on mirror polished
samples. All my steel samples were the same composition, but I think different alloys will yield slightly different colors.

A few years ago I tried to use the salts without added MgO and a burner set up that was limited to about 600°. This really didn't produce satisfactory results on a low carbon steel receiver.

I can't prove it, but the MgO seems to aid oxide growth. The higher temp. really is key to good color and I am satisfied that the Brownells salts are capable of doing a good job.

OB