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How To Easily And Inexpensively Blue Tempered Steel At Home

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Bluing is an attractive means of decorating tempered steel with a rich, dark blue patina finish. It's common to find firearms that have been blued, but other items can blued, as well. In fact, practically any tempered steel, from knife blades to wrenches to decorative fittings, can be blued. While there are a number of ways to blue steel, many of them involve the use of expensive chemicals and equipment. However, below is how you can perform bluing at home using relatively low-cost chemicals and common equipment you probably already have. Here is what you need and an easy-to-follow procedure for bluing:

Tools and materials needed

  • Glass container

  • Triple-ought (000) steel wool

  • Paper towels

  • Funnel

  • Timer or stopwatch

  • Stiff wire or metal coat hanger

  • Kitchen oven

  • Ferric chloride solution

  • Distilled water

  • Measuring cup

  • Trisodium phosphate powder

  • Liquid dishwashing soap

  • Rubber gloves


1. Polish the steel - for steel to be blued successfully, it should be polished to remove all stubborn surface impurities and deposits. To polish your steel, vigorously rub the surface of the steel with very fine steel wool (triple-ought or '000' grade) using a circular motion. Periodically rinse the object with clean water and dry it with paper towels to remove loosened particles. You may also use a 600-grit sandpaper pad if you are unable to locate the appropriate steel wool, but be sure not to use sandpaper with a lower grit rating in order to avoid scratches.

2. Clean the steel - once the steel has been thoroughly polished, it needs to be cleaned to eliminate any traces of oil or other chemicals. Prepare a solution of trisodium phosphate (TSP) by mixing a tablespoon of TSP powder per cup of warm water; make as much solution as needed to immerse the steel object completely.

Place the steel object in the TSP solution and allow it to soak for ten minutes. Remove the object and rinse it in cold water, then wash it in a solution of warm water and liquid dishwashing soap. Rinse the object and place it on a stack of clean paper towels to dry.

3. Immerse the steel in the bluing solution - after the steel object has air dried, you need to prepare the bluing solution. Mix one part of ferric chloride solution with three parts of distilled water, and as with the TSP solution, make as much solution as necessary to immerse the object. Pour the bluing solution into a sufficiently-sized glass container.

Next, put on a pair of rubber gloves to protect your hands and prevent transferring skin oils to the object. Grasp the object and slowly lower it into the bluing solution to avoid splashing. Allow the steel to soak for 20 seconds and remove it from the bluing solution. Rinse the object under running cold water for at least 2 minutes to remove the solution from the steel and place it on a new stack of clean paper towels.

The bluing solution may be reused with future bluing projects, so carefully transfer it to a clean, empty glass bottle with a funnel and seal it tightly. If you wish to dispose of the bluing solution, then pour baking soda into the container to neutralize it, then wash it down a drain with a copious amount of water.

4. Heat treat the steel object - after soaking the steel object in diluted ferric chloride solution and rinsing it thoroughly, fashion a piece of wire or metal coat hanger into a hook that can be used to suspend the object as it is heat treated. You may need to shape the wire into a "cradle" if the object does not have any convenient protrusions or holes into which to insert the hook.

Preheat your kitchen oven to 450 degrees Fahrenheit and hang the object inside the oven so it is suspended in mid-air. Do not allow it touch any of the racks or side of the oven during the treatment process. Set a timer for 30 minutes and allow the object to be heated for this amount of time.

Once 30 minutes has passed, remove the object from the oven and allow it to cool naturally; do not submerge it in water. After cooling, the object should be evenly blued and may be lightly oiled with an all-purpose machine oil to help preserve and enhance the finish.

For more information on this process, you could contact a thermal processing professional at a company like Pacific Metallurgical Inc.