Blueing salt and solder pot

Dr. Jon

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A fine watchmaker introduced me to Brownell Blueing salts. This is a solt that melts a bit below the blue tempering temperature. I finally realized that small solder pots will work well for blueong smallitems especially with odd shapes.

Here is the setup. setup pot.png

The can in back is small container with my supply of Brownell NitreBlue. Brownell is gunsmith supply company and they sell it in 10# lots. My friend gave me this smaller supply. I keep it in a sealed can because the stuff absorbs water from humid are gets wet. The 10# package costs about $66 plus shipping.

This solder pot is avialbale from several suppliers and cost about $30. This 50mm cup 150W model.

I was trying various setting and this one did nto melt the stuff.


At 6 on the dial the crystals melt.

melt.png

The surface has some froth, Note that the label is in Chinlish and Man is a typo for Max.

At this temperature dipped steel comes out dark straw.

At ~6.5 the surface becomes clear and turns steel blue.

Here are the hands I blued
hands.png
They are more uniform than they appear here due to uneven lighting.

I held each with tweezers for about 30 seconds.

When powered down the salt forms a white solid. I am keeping the pot in a sealed container to keep it dry. bluemelt.png
 

praezis

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Thank you for this variant of blueing!

I suppose, the color appears after removing from the molten salt. Doesn't the salt stick to parts and cause stains?
Is the pot removable or fixed to the device?

Frank
 

Jevan

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Jul 31, 2014
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I have often used bluing salts for longcase hands, a Potassium Nitrate & Sodium Nitrate mixture.

With regard leaving a deposit, if you take a hand out of the molten salts & dunk it in water all traces of the salts are removed.
If you don’t dunk a white crust appears but again if subsequently put in water the crust will dissolve.

Stand back when dunking as the bluing salts, if hot, will react & spit as the hand is quenched, it is not nice stuff to get on the skin.

It would be nice to blue properly but I never mastered that art, I can’t really remember the details, possibly a lecture, but I remember a restorer of great repute, Mr Dan Parkes, saying he had at times taken a day to blue hands properly, in the trade I was in that is just not economic.
 

Dr. Jon

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My view is that this is proper blueing. It is not really a shortcut. The items has to be prepared, polishde anb cleaned just as it for flame blueing but this process is much more uniform.

FWUW I visted a very high end watch manufacturer and got a lesson in how they hand blue hands, They use a large soldering irong fixed to a large copper block.

As Jevan wrote, the salt goes away with a simple water rinse.

Since I hold the tweezers in my hand it is also hand blueing.

My only addition to all of this is my discovery that very inexpensive solder pots are a good size and have adequate temperature control to due several stages of bluing .

The pot is not removable and I think it is spot welded to the heater. This is why I keep the entire unit in an air tight container.

I do this in a bathroom on a Corian counter but I put a slate 12 inch by 12 inch tile between teh unit and the counter top. This is to protect the counter from stuff that might splash out. When I was using a torch I found that I coudl get the salt hot enough to bibble and if water gets to it the hot salt with pop out.
 

Jevan

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Jul 31, 2014
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Just to clarify, I had no intention of suggesting bluing with salts is not proper bluing but merely wished I had the ability to blue over a flame, traditional rather than proper would have been a more sensible word to use in my previous post.
 

Betzel

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I agree the blueing done by this process is about as good as it gets, deep and even. And I have heard, from people who speak as though they know, the most dangerous element in this process is moisture --of any kind-- as the vaporization of any water (however formed) can cause the bath to violently explode. Old timers used these on long firearms with incredibly good results, but the training process has its risks. Humidity, temperature changes, hidden spots of water from rinsing larger work, etc. Good thing clock hands and strike components are fairly simple!

Super clean and drier than Phoenix in the summer. Be careful!!
 

measuretwice

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Wondering about colour. I've blued by taking parts up to a blue tempering temps and also using cold blueing, but have not tried hot bluing or slow rust bluing. At least from cold bluing its a very different colour, almost black, that you get vs temperature bluing (in steel).

Obviously there 's a photo, but It can be difficult to get sense of colour from photos - i.e. different white balances etc. How would you say the colours compare...and is the objective a closer to black finish than temperature blueing?
 

wefalck

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I have blued screws using my electrical hot-air soldering unit that can be ramped up gradually up to 450°C.
 

Betzel

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The best work is definitely more of a dark-dark blue than black in my view, but if you kept it in long enough it would get dark. Maybe Dr. Jon will try it and report back? To me, a "midnight blue" is more visually pleasing than black, but that's just me. Photos are hard, so I agree holding it in your hand on a slightly cloudy day after oiling and wiping it down is the best way to experience fine blueing workmanship up close and personally. Like Damascus, it's just awesome to admire.

I'm a flame-blue (temperature) guy with a collection of Asian butane lighters to beat the band. I still end up with violet streaks or cross-over to green on parts when I'm in a hurry, can't see well, or I'm not paying enough attention. When I do hit it perfectly with flame, it's always on brass chips, super-clean, slow and even. I've gotten lucky with larger work on a gas-burning stove when the wife was out doing something else, but not always. Propane is hot, but whatever works! I've never done salts (just watching guys on you tube doing it on an electric stove with a thermometer is close enough for me) but if the temps are just right, it seems easier to hit the perfect color evenly all-around with this method as the work is totally surrounded by the heat?

I think most rifles and pistols made during the 20th century were blued with these salts, not only to preserve the steel, but to show off their range of craft and skill. That dark, deep blue can stand up to more than a few passes with 0000 steel wool with no visible change and has often lasted more than a century. I think the smiths used long steel slop-troughs filled with salts powered from below by natural gas (rifle-barrel soup?) and (slowly) dropped the parts in from above, and at a safe distance in case of error. Hazardous in so many ways. The earlier craftsmen who did all this just with flame on pieces that were perhaps even larger and heavier were far better craftsmen, as usual. Not sure I could tell the difference in the end when a master has done the work by any method, but some quick work had "racoon tail" waves as the heat-time with flame was not even.

I've seen guys blue in an oven, but never with a hot air gun. Bravo, wefalck! :) Cold blueing (oxpho-blue) has never worked well for me, but I've heard if it's warm it's better, and you have to repeatedly use steel wool to finally get it to look great, but it can be done. The only way for hardened steel. And, the chemical vapors from that stuff will kill anything beautiful that's nearby, even wafting from a q-tip. The nickel lathes were usually blued, but the last generation of G. Boley watchmaker lathes (painted green, like the F1) were --I think-- just chemically blackened (but way better than how the Asians do it, and no foul smell!). The rust process may be called browning. Not sure, but it has an interesting look, too.

Most of the high quality watchmaker lathe components I have display a fantastic job of blueing, as do brackets and some strike train components, springs, etc. on clock movements. Germans seem to have done it more than the English, and the French are in the middle, but it's just a casual observation. Dr. Jon, can you try to get a test piece to turn black the next time you cook your soup?
 
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Dr. Jon

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With the solder pot I have the color is matter of dial setting. The range is from dark straw which I got to blue which is the dark before purple, which I regard as over blued.

With this method you try sample pieces at the lowest melt setting until you get the color you want. Before I discovered the pot I used a metl container and a torch (propane) to heat the molted salt but I found the the pot often flared up., It was very small and I used a fire proof surface, but color was very tricky.

The temperature controlled solder pot produces consistent and even results. The salt people recommend holding the item in teh pot for several minutes. I found 20 seconds worked well, which is fortunate, since holding regular tweezers that near get painful after that time. I'll use longer tweezers next time. At the price I think its just too simple not to use it.
 
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Betzel

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Thanks DJ. Since you have the thing working, would you please someday take a test piece of tool steel (like a broken stake. etc) and cook it for a long time or a couple of times to see if it can be made "black"? We know about "cold" chemical blackening, and oil blackening (like tool post holders) browning and blueing, etc. so (at least) I wonder if these salts can also turn steel any darker than deep midnight blue --if you work it long or far enough?

Thanks if you can bust this myth!
 

Jevan

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Jul 31, 2014
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I use salts in a large cast-iron frying pan, I heat the pan on a portable single electric hot plate with additional temperature control achieved using a propane blowtorch.

In my experience if a hand is left in too long the next step to the dark blue colour is a dull light grey colour, at this stage the only course of action is to re-polish the hand & start again.
 

gmorse

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Hi Jevan,
In my experience if a hand is left in too long the next step to the dark blue colour is a dull light grey colour, at this stage the only course of action is to re-polish the hand & start again.
That's because the temperature has risen above that required for the dark blue to develop. Once the salts have melted, further heating will raise their temperature, and the colours will go through their normal progression depending on the temperature; it's the same effect regardless of how the heat is applied.

Regards,

Graham
 

Betzel

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it's the same effect regardless of how the heat is applied.
Okay. That's exactly what I was wondering. I know the sad feeling of turning things green (grey, etc.) all too well.

So blackening is a different process cold with chemicals or using heat with oil.

Thanks guys!
 

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