An article from 1959 by Chas. B. Hunt (Geotimes, Vol III, No. 8, May-June
1959: 8-10, 34) supports this argument from a slightly different direction
and suggests that the WWI timing is coincidental. Hunt notes that this is
the same  period that the use of the various bottle-making machines became
more common.  He argues that machine production required generally more
care in glass formulae than did hand production. The result was a decline
in those impurities that caused color in the first place, as well as a
decline  in the use of manganese to neutralize those colors. He notes that
prior to WWI, and the introduction of wide-spread machine manufacture,
chemical analyses indicated that manganese ranged from 1.0 percent to 0.1
percent. Modern (i.e. late 1950's) glass was likely to contain less than
0.001 percent manganese. He doesn't list the earlier iron ratios, but in
the late 50s iron was at about 0.02 percent.

Robert Leavitt


At 9/22/2004 02:07 PM, you wrote:
>       I posted the following information on HISTARCH in January of 2002
>which is a discussion on the role of tank furnaces in causing the switch to
>selenium as a decolorizer.  The tank furnace had more to do with the switch
>to selenium than supplies during WWI.  Bill Lockhart has a much longer
>discussion of this that will be published in Historical Archaeology in the
>near future.
>
>Solarized glass and the change to selenium as a decolorizer.
>
>       The switch to selenium as a decolorizer began before WWI.  Because
>the Owens Automatic Bottle-Blowing Machine worked from a tank furnace, it
>helped bring about the switch to selenium.  Manganese dioxide was not very
>stable in a tank furnace because it is difficult to maintain an oxidizing
>atmosphere in such a furnace.  Selenium was much more stable in that
>environment.  One of the earliest publication of information on the used of
>selenium as a decolorizer came out in 1911 (Angus-Butterworth 1948:68-69).
>Keep in mind that the half of the bottles produced in the United States in
>1917 was being made on the Owens Machine.  I have not seen very many
>solarized Owens-made bottles.
>
>Angus-Butterworth
>       1948  The Manufacture of Glass.   Pitman Publishing Corp. New York
>
>For a discussion of this transition, see "Impact of Mechanization in the
>Glass Container Industry: The Dominion Glass Company of Montreal, a Case
>Study."  Historical Archaeology 1983 volume 19, no. 1:38-50.
>
>       Tony McNichol and I gave a paper at the SHA on dates for
>suction-scarred bottoms and we have been gathering information on the
>subject.  Opinions we do not need, however comments with citations would be
>most appreciated.
>
>George L. Miller
>URS Corporation
>561 Cedar Lane
>Florence, New Jersey 08518