[ Ref. Bob Caletti in 150520 MMDigest ]

Hello Bob,  In my music box workshop we use the following bluing
process quite a bit. We have long since dispensed with using any of
our old formula books but I believe the following process from our
1966 (17th Edition) of Machinery's Handbook will help you, in addition
to my own quick notes.

  "Bluing Steel by Heat-Treatment, from the Machinery's Handbook

  "Polished steel parts can be given a blue color by heating in hot
  sand, wood ashes, or pulverized charcoal.  Place the substance in
  a iron receptacle and stir constantly, while heating, in order to
  heat uniformly.  Heat just enough to char a pine stick.

  "The parts to be blued must be absolutely free from grease.
  They are placed in the heated substance until the desired color
  is obtained.  Further coloring is then checked by immersing in oil.
  Small parts are sometimes heated by Bunsen burner or by laying upon
  a heated plate.

  "For a light blue color, heat in sand or wood ashes, and for
  a dark blue use pulverized charcoal.  The quality of the color
  depends largely upon the fineness of the finish."

I've found that the simplest way is to first purchase a new laser
pyrometer which can be found inexpensively in many hardware stores
today.  Before you begin the bluing process it is highly critical to
bright polish and thoroughly clean the part you are wishing to blue.
This includes removing any fingerprints.

I then heat the pan or the sand depending on the size or number of
parts to be blued, and check the temperature with a pyrometer.  I've
found the ideal temperature is 560 degrees Fahrenheit for a perfect
blue, and do not forget to constantly check the color as it evolves
and darkens.  When the part has reached the blue you desire, pluck
the part from the sand or the pan with a pair of utility tweezers and
cool in oil so that the color will not continue to darken.

I hope this answers your question.

Christian Eric - Antique Music Box Restoration
Costa Mesa, Calif.
musicbox@jps.net.geentroep [delete ".geentroep" to reply]