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  for Metal Finishing since 1989
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Small bluing operation

 

I make custom knives, and I want to set up a simple small hot bluing operation to blue small parts, I need some info as what to do and what not to do to get good results.

Thanks,

Marvin Solomon
Cold Springs Forge - Paron, Arkansas

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Marvin,

I have done hot bluing for years and hope I can help a little. You might do a web search for gun smithing supplies to find the proper chemicals, tanks, etc. My larger tanks are black iron with pipe burners for heat. I use a simple electric 2 burner hotplate with large coffee cans for small items. I use a caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] solution that is heated to 300 °F. for the bluing, and a hot (175 deg) degreasing soap solution for cleaning. The most important part in bluing is SAFETY. 300 deg caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] will eat right thru leather, wool, and skin; rubber gloves ⇦this on eBay or Amazon [affil links] and a face shield ⇦this on eBay or Amazon [affil links] are the minimum you should use. The metal must be chemically clean, a fingerprint will mess up a bluing job. Temperature is critical, so a good thermometer is a must. The metal must be finished as you want it as bluing only colors what you put in. A simple operation once you understand it.

Good luck.

Ed Kay
- St. Louis, Missouri, USA

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2006

Hello all!

I read with interest all about steel blueing at your forum and noted that it looks like a very simple and effective bluing method widely known among russian hobbists is not known in US. Recently I have nicely reblued my C96 Mauser pistol using this method.

This is a hot process so not suitable for double barreled guns. The chemical needed is the only one - natrium nitrat (NaNO3, very chip, sold in flakes, used in agriculture, also known as Selitra). The all you need are: 1. preferably new 10 dollar nichrome spiral type electric heater of 1kWatt. 2. suitable size metal pot (I used half of 1 gallon can cut with scissors). 3. piece of cardboard or old plywood 1x1 meter. Put flakes into pot and heat untill flakes melt (approx 320-350C). There are almost no fumes if pot was clean enough. When flakes became a fluid add more if required to top over your work. Parts to be blued must be stripped of old blue and polished. It is not required to do chemical degreasing, just whip parts with cloth wetted in acetone ⇦this on eBay or Amazon [affil links] Warning! highly Flammable! and dip them into hot bath and watch (I noted that even not thoroughly cleaned parts, with fingerprints also come out nicely as fat gets burned away easily). In 3-5 minutes they turn to be of nice dark blue color, the longer the darker. When done, get parts out using old pliers and hit them over plywood to smash liquid film out. Be careful do not cach a splash. Some use to dip hot parts into hot water that causes frozen remains of chemical to crack and come off easily. The resulting finish is of very nice look and extremely hard to scratch even. However, it can be washed away in hydrochloric acid. Different carbon content metals may take different coloring shades, if you have means to control temperature the color on different metals can be adjusted to be uniform. Ones who want to try this must be carefull as melted selitra is very hot and any drop of water in it (from sweating) may cause hot splah in your face.

The other hot process I was adviced (but not performed):
700 grams of caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link]
250 gr of natrium nitrit (sodium nitrite)
200 gr of natrium nitrat (sodium nitrate ⇦this on Amazon [affil link] )
get dissolved in 1 liter of water and heat to 140 °C. Parts are blued in boiling solution.

Good Luck,

George Ukrainsky
telecom - Dubai, UAE