[Plinker82]

So yesterday was the first time I had been around hot bluing using oxynate #7 and it was quite interesting. This was performed on a Winchester 62A which I had hand polished and sanded out all the rough spots on for weeks. All the parts turned out real nice except for the barrel and receiver. I noticed the receiver had some blotches in it after being in the tank for 10 minutes. I then decided to use some metal polish to clean up the blotches since I figured I had nothing to lose anyway, washed off the polish and stuck it back in the tank. It really cleaned up the reciever perfectly and I was really satisfied with the finish. Problem is I found a few MINOR blotches on the barrel so I used a little polish to buff out the imperfections and put it back in the tank. When we took it out... the finish was horrible. The barrel had blotches ALL over it where it was nearly perfect before. What would cause the blotching? I suspect it could have been the polish that wasn't clean off completely but I used strong detergent and rubber gloves to clean the metal. Also, I will be trying it again and was curious if the finish really needs to be cleaned off before going back in the tank. I was thinking of just hitting the areas where the finish wasn't which would save me some prep work... would the "old" and new finish blend?

Thanks!

[dfariswheel]

Blotches are almost always a symptom of contaminated metal.

Possibly the rubber gloves left contamination.
The best way to blue is to polish the metal and not touch it with anything after polishing. Use wire or wood dowels to hold the parts while transferring to the cleaning tank and blue the metal as soon after polishing as possible. Sometimes gloves have dirt on them that can contaminate the metal.

You may need to look at what chemical you're using in the cleaning tank and possible use two cleaning tanks.
Often, oil or other contamination that gets cleaned off in the tank floats on the surface and when the parts are removed the contamination is picked up by the metal as it comes out.
This is where a two cleaner tank system can do a better job.

Last, removing the parts and polishing then putting them back in the bluing tank is a sure way to ruin the job.
About the only way to correct this is to start all over with polishing the parts and running them through the cleaner and bluing tanks again.
It's very unlikely that doing some polishing then attempting to blue the parts will look like other than what it is.... a botched up.

[Plinker82]

What's the best generic degreaser? The stuff we used was from brownells and my friend wasn't impressed with it. We were using the local gunsmiths tanks. Would break cleaner or acetone work well to clean the metal?

[brickeyee]

Blotches are almost always a symptom of contaminated metal.

this.

you have to clean the4 gloves also each time you go to use them.

What's the best generic degreaser?

I much prefer MEK since 111-Trichlor was taken off the market.

[Jim K]

I recommend not handling the parts to be blued with anything. Drive wood dowels into the muzzle and chamber ends of the barrel and leave 3-4 inches sticking out as handles. That will not only keep from bluing the bore (not a big deal, but some customers don't like it) but provide a means of handling the barrel or barreled action without touching it.

Jim

[dfariswheel]

You can use Acetone, brake cleaner, or a soap cleaner like one of the aggressive grease cutters to PRE-CLEAN the metal BEFORE it goes to the bluing system.

The real cleaning is done in the first tank and it's usually a hot caustic chemical cleaner which you boil the parts in.
This cleans the parts and pre-heats them.

This is why bluing setups use multiple tanks.
A good set up has a minimum of three tanks. One cleaner tank, a bluing tank and a tank of boiling chemical that STOPS the bluing process and prevents bluing salts "bleed-out".

A really professional system has TWO cleaner tanks before the bluing tank, a bluing tank, a chemical stop tank, and a tank of warm oil.

[Plinker82]

The system we were using has a cold water tank, boiling water tank, bluing tank and water displacing oil tank. I guess what I need to figure out is WHY the bluing had a "marble" look to it to begin with. The metal polish cleaned up the marbling fairly quick with little effort but I realize that I shouldn't have to use it and run a risk by doing so. I think the problem may stem from oil contamination when parts go from bluing tank to the wash to the oil bath and then used again to blue more parts. The friend helping me doesn't blue a lot of highly polished parts so these imperfections we are seeing now are not easily noticed when bluing the typical screws and knurled parts that he is used to.

[Old Dog Man]

If the bluing tank is used fir bluing other parts it could be that there is a contamanant in the salts that is causing your problem. Any nickle or aluminum that may have been put into the tank will cause spots on a blued finish. Al

[Plinker82]

We cracked open a new bucket of Oxynate #7 so the salt bath was fresh to begin with.