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Old July 4, 2013, 06:10 PM   #1
guncheese
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bluing chemicals

ive decided to give a go at hot bluing some of my parts
and yes i know it can be messy and dangerous
but rest assured i can take the necessary precautions (in a former life i etched psychical parts and circuit boards, not to mention stainless finishing)
ill only be doing small parts, frames, slides and such
the question is, is there any difference in the finish color with using sodium nitrate versus potassium nitrate as the oxidizer ?
and also when is the proper time to buff up the fresh finish before running it back into the salt bath for deepening?during the hot water wash or after the wash when its in the water displacing oil? or no difference? sure would be easier in the water
thoughts and suggestions appreciated
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Old July 4, 2013, 06:45 PM   #2
Dixie Gunsmithing
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Caustic baths, like Oxynate #7, contain both sodium and potassium nitrate, and have to come to a boil at around 280+ degrees (290 for Nickel Steel), which is controlled by either adding salts or water. If you're going to blue frames on single shot shotguns, etc, then there is a cyano additive to keep them from turning a red or purple hue. Also, every caustic salt manufacturer has their own recipe, and they tell you to do things differently. This will not work on stainless, and takes another type of salts. Also, don't add the cyano additive until you have ran the bluing bath three times, with guns, as it can kill it.

What I have found, is that hot water rinses, with #7, are mainly unnecessary, if you use compressed air to get any remaining salts out of threads on barreled actions, etc. Plus, if a little white powder was to leach out and appear, then tell the customer to take a toothpick and remove it, then put a little oil on it. I've never seen that hurt one, and it rarely ever happens.

You can get by with four tanks, two heated, and two with cold water to rinse in. The first heated one holds cleaner, like Dicro-Clean 909, which is boiled. Next, a cold water rinse, and then into the bluing bath for 30 minutes. After the bluing, a thorough rinse in the second cold water bath. After, use some compressed air on any threaded assemblies, another rinse, and then a dip in water displacement oil.

You either need to blue the parts right after their polished, or spray them down with Brownell's Hold, and do them a day or two later, when you have a batch ready. No more than two days is what I do.

I suggest buying a rubber apron, face shield, and rubber gauntlet gloves to protect you from splashes. I burnt two fingers on hot bluing salts years ago, and still carry the scars.
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Old July 4, 2013, 07:06 PM   #3
guncheese
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ohh yes there will be apron and face shield and gauntlets! im getting to old to be permanently mamed!
so ill grab a couple pounds of both the nitrates
this will only be small batches and small parts
i guess in this process experience makes perfect
but i want to give it a try
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Old July 4, 2013, 07:24 PM   #4
oldgunsmith
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Art Mashburn's original formula was 16 lbs. sodium nitrate and 16 lbs. caustic soda beads in 32 lbs. (about 4 gals.) of water. We added a couple lbs. of TSP.
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Old July 4, 2013, 07:49 PM   #5
guncheese
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TSP right in the blend?
what was the result of that? clean as it rusts ?
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Old July 4, 2013, 08:59 PM   #6
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Some cautions. Caustic salts dissolve both soft solder and aluminum. So tossing a set of double gun barrels in the tank can result in two single barrels. And trying to blue an alloy frame revolver results in, well, nothing.

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Old July 5, 2013, 07:26 AM   #7
guncrank
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bluing chemicals

I use find it easier to buy the salts already made
Prefer Du-lite myself.
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Old July 5, 2013, 02:15 PM   #8
guncheese
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so i have the 8lbs of sodium hydroxide and 2 lbs each of potassium nitrate and sodium nitrate coming
and today im going to attempt the death defying feat of unelectroplating nickel
(new word there) and then stripping the copper flash off of the small parts of my 1911
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Old July 5, 2013, 04:25 PM   #9
oldgunsmith
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TSP in electric dishwasher detergent is what makes the glasses dry clear and without spots. Small amounts tend to do much the same in the right caustic solution. Contributes to a smooth, even blue without spots or varying discoloration.
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Old July 5, 2013, 04:37 PM   #10
guncheese
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ahh sort of acts as a surfacant
good idea, i didnt see any at wally world today
but im sure Menard's or the hardware store has some

the "unelectroplating" worked great
just used battery electrolyte with a bit of glycerin as a fining agent
and a 7ah gel cell with a few boolits soldered together for a electrode
and the part as the anode, took less than a minute to strip the nickel off
and a unexpected side effect of also taking the copper flash off as well
giving them a bit of a ammonia soak to make sure the rest of the copper is gone
then ill cold blue them for the short term
the Fair Lady says im a mad scientist
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Old July 5, 2013, 05:06 PM   #11
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Be sure that all the copper is gone, as a small amount will kill a bluing bath. A single penny can kill a bath of 40 pounds of salts. Aluminum can kill it also, but to what extent, I'm not sure, but copper is really bad.

What you'll be doing, by what you mentioned, is called reverse-plating, by reversing the polarity on the plating process. In this, the anode becomes the cathode. You can use regular battery acid, or mix your own, using muriatic acid and water. Remember, the acid is always mixed into the water, and not vice-versa. Use a good glass container, or acid-proof plastic, and a good hefty power source, preferably one you can control the current with.
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Old July 5, 2013, 05:13 PM   #12
Dixie Gunsmithing
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oldgunsmith,

I can see TSP working well, but they have about stopped using it in home products by what I've read, though you can still buy it by itself. I would like to know if it would work in Oxynate #7, but because I don't know who actually makes it, it may already be in it, as Brownell's does not give all the ingredients, just that its nitrates. I think they buy it, and label it themselves, but from who, I don't know. I stick with it, as I've used it now for 30 years, and know all the possible problems by heart, what few there are.
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Old July 5, 2013, 09:00 PM   #13
guncheese
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on the parts i "unelectroplated" i spent some time polishing and dehorning, just the GS,SS,MSH and the ambi safety and wow i have gained a new respect of the work you guys put into these things
i just super blued them to keep them from rusting before i finish polish them to go into the salt tank
and i must say the GS turned out like WOW!
and the other bits either are made of crap (likely) or those small parts are just really hard to get right or i guess both.

Last edited by guncheese; July 5, 2013 at 09:18 PM.
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Old July 14, 2013, 10:02 PM   #14
triggerman770
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bluing chemicals

quote"Some cautions. Caustic salts dissolve both soft solder and aluminum. So tossing a set of double gun barrels in the tank can result in two single barrels. And trying to blue an alloy frame revolver results in, well, nothing"

unless you are using Du-Lite Steelkote. it results min a hellaceous boil over.
the Du-Lite eats up the aluminum and can attach it to the tanks, resulting in a wasted batch of salts and a trip to the sandblaster for the tank.
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