doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Infrared Thermometer for Nitre Bluing.

Anyone ever use one? It seems that it'd be easier and better to use than one with a metal probe. Especially when using a smaller container for parts like trigger guards, etc.

Thanks
Ken

Ken, I've used one many times and own one, but never thought of using it as you suggest. By nitre blueing, I assume you are talking about immersing polished steel parts in a molten bath of saltpeter or potassium nitrate. If so, just bringing the pot to a temperature where the potassium nitrate is completely molten will have you at a temperature that will turn the parts blue without the need to monitor the temperature. Once molten, just back off on the heat enough that it doesn't begin to solidify.

Have you heard about the little trick of inserting a long lag bolt into your nitre bath before it cools and solidifies, and then unscrewing it to leave a vent hole to prevent pressure build-up the next time you heat it. A rupture through the still solid crust at 633 degrees F will ruin your day. Just another tip from Brownell's "Gunsmith Kinks" that makes those books worth every penny.

Thanks.

Yes, That's exactly what I'm talking about. I'd think it'd work well, pointed at the melted solution, mainly to be able to keep it from getting too hot. I've read if it gets too hot the colors won't come out well.

I've heard of the "bolt trick", folks say it was listed in one of the "Gunsmith Kinks" books. I don't have the books yet, but there seems to be lot's of info in them.

Regards
Ken

Ken, that's the understatement of the year. Four volumes are packed with tips and techniques from guys who make a living working on guns. Of course, some of it will be all but useless to a guy who works on nothing but old doubles, but when you get the complete set, you will kick yourself for not doing it sooner.

I suppose you could overheat a nitre bath, but just dropping the heat after it completely melts will keep you in the proper range for turning steel blue. The infrared thermometers seem to be quite accurate if properly calibrated, and you could certainly use it if you have one. But I wouldn't go out and buy one specifically for that sole purpose. I've heard that the nitre bath is also very good for tempering springs after hardening, but I haven't tried it yet. Have you?

Not yet. I've been considering the lead bath route though. On the few springs I've done I've often broken them, trying to do it like Jack Rowe. I have to make a decision soon, I'm shortly going to be doing complete disassembly in preparation for Case Coloring. I wasn't aware the Nitre bath would work, but why wouldn't it?

Haven't used it for that but they work well to heat barrels that may have water from boiling. You can get it hot enough to turn the water to steam and not hot enough to melt solder.

Ah, thanks Mark,

Another good use for it. Got any preference for the day of our meet in CR? Friday, or Sat early would work for me, I've got my eye on an LC I have to meet about on Sunday. We'll have to ask Larry as well.

With nitre bluing, you may be looking at heat color of steel. It can be used to produce other non blue colors based on temp changes. For both getting the right color or using it to nail the right temper for a spring, I'd consider monitoring the temp more accurately.

I'd think a good conventional thermometer or thermocouple in the correct range would get you closer to where you want to be. If you weren't aware of it, Brownells has a good pdf of the nitre bluing process even if you decide to go the stump killer route. Only thoughts, and best of luck with it.

Thanks Craig,

I'd heard that Stump Killer works, and I think I'm going to add the 10% Manganese Peroxide as per Oscar Gaddy. It appears to speed up the process. For a tempering bath, I agree having a pot that would maintain a consistent temp would be better.

I've been looking for a suitable smelting pot for the tempering bath that is controllable, then I realized I can use the same furnace (small kiln, digitally controlled) I'll be using for case coloring. It'll be easy to open the top and "shoot it" with the infrared thermometer.

Regards
Ken

Just to round things out a bit, I mentioned stump killer only as a source of potassium nitrate, the stuff that keith had mentioned earlier. I'd be a little careful with top openers and salt baths, you may mess up your kiln, have a tough time accessing color changes, but most of all, you have to look in right in the line of fire if some thing splatters.

Consider checking out the pdf. Temp changes as low as 10* and certainly 20* will change the colors. Maybe think camp stove style burner setup and an appropriate material pot to dip in, maybe.