doublegunshop.com - home Forums General Discussion DIY Gunsmithing @ doublegunshop.com Hot plate for nitre blueing ?

I was wondering if anyone has used a hot plate/cooker ring for the above.
I use the salts from Dyson and up to now, have been heating it in a stainless beaker over a small gas camping stove. I find it can be time consuming as it's easy to get the molten salts too hot even at the lowest flame setting so have been taking the beaker off to let it cool then during the re heat, dipping the parts in and watching the colour change until they're the nice royal blue I wanted.
I've seen a few ways to do the job from kilns to burying the parts in brass filings on a hot plate etc but thought a simple hot plate or single ring cooker/hob could be the way to go for heating the beaker of salts to the right temperature then relying on the thermostat to hold it there.
I'm sure there will be some trial and error involved getting the temp correct and constant but I've seen a 1500w electric mini hob for �12 ($15 or 4 beers ) so thought I'd ask if it's worth going down that road, if so, and the salts are held at the correct temp', could all the parts, large and small, be dropped in at once and pulled out when the desired colour is reached ?
Any ideas or input gladly received.
Thanks,
Nick.

Purchase a high temperature cooking thermometer this takes the guesswork out of nitre bluing. Take a look on ebay for an all stainless steel type, they are usually not much money.

You need a heat source that will do 600 degrees F. For smaller parts a Lee lead pot works well. YMMV

Hi Damascus, I've got thermometers that go high enough, it's finding a heat source that's more controllable than my ye olde camping stove that I'm looking in to.
It's mainly to save time (if possible) while still getting every part the same shade of blue. It's one of the little jobs that I really enjoy but can easily turn into half a day if I don't keep my eye on the ball and go too hot.
Thank you for the suggestion though.

Hi Mark, thanks for the input too. I looked at various lab hot plates and lead/jewellery pots but the prices were a bit to high to justify the outlay. I will probably buy the cheap hot plate as it can still be used for boiling off small parts (and making a cuppa) even if it proves to be useless for the nitre pot.

Aaah! grass hopper!! Constant temperature source is a very difficult ask. I feel sure that you will have to keep your eye on the ball even with a single ring electric cooker, because the hysteresis of the thermostat type used in those cookers has a rather wide on off spread. A way to smooth the temperature swings is to use a metal container with a layer of sand between the heat source and the bluing salt container, start with about an inch of sand.

I see, does the sand act as a heatsink and steady the temperature ? It's got to be worth a try then.
I'd looked on a chemistry students forum and one guy gave the part numbers for a pretty accurate thermostatic control and a temp sensor with digital display which were quite cheap. He'd modified a single ring plate element cooker and reckoned he could make it almost as accurate as the laboratory version the original poster needed but couldn't afford. Feels like a project egg has just hatched.

Here's an off-the-wall method that I intend to use. I installed a digital controller on the small electric kiln I use for case coloring. It should hold the pot at the correct temp with no problem, and it's top loaded. It'll also be easy to shoot the temp with my infrared thermometer.

Regards
Ken

Hi Ken, thanks for the suggestion. At risk of sounding like a miser, I'd not planned to spend much cash . It's got me thinking though. If the heat could be regulated accurately enough and then use a sand 'jacket' around the beaker on the hot plate it should act like a kiln.
The question now is. If, the molten salts could constantly be held at exactly the right temperature, would the workpiece stay the same colour whether it's dipped in just long enough, or, left in for a minute or two ?
Would the oxide layer stay the same colour or would it's thickness or density alter and change the colour or go dull with scale?
I wanted to see if it was possible to wire the whole batch of parts together and do them all in one go.
If the difference in time, albeit seconds, that different sized pieces will reach the temperature of the salts around them wasn't an issue, it could be a time saver.

Nitre blue will also give a jet black color but the target temp for that is 830 degrees. Talk about it being tough to get them that hot. I normally can get my salts up to 725-750 on a gas stove with an aluminum foil heat shield to retain the heat in more. And i get decent color for trigger guards and triggers at those temps.

I have looked into furnice pots a few times, but they are a lot of money.