I just returned from an excavation and somehow missed the first posting on this
subject.  There are some pretty major problems with much of the Kendrick material.
We have learned a bit since the early 1960s.

Her solarized amethyst data are not very accurate.  I looked up the import records
(as part of an article that the journal of HA has been sitting on for quite a while), and
we never imported any noteable quantity of manganese from Germany.  The move
away from manganese decolorization was because of a change in manufacturing
techniques, not a war issue.  About 1920 would be a closer end date.

Kendricks used empirical data (sometimes a great method, sometimes not) derived
from bottle observation.  According to chemists in the 1930s (as I recall--the date
may be a little later or earlier), selenium was never the cause of "straw-colored"
glass.  I will save the punch line about the real culprit when I publish the next article.
Selenium is still--in the year 2003--used to decolor glass!!  References to straw-
colored glass appear much later than 1930 (1970s, I seem to recall), and it is
probably not an accurate dating device.  I do agree with Kendricks that the bulk of
glass that will solarize to a "straw color" was probably made during the ca. 1914-
1930 period.  In any event, there are no "solid" dates for the process  (which
probably was used as early as the 1890s and at least into the 1950s).

When citing Kendrick's work, remember that she is also the one who said you could
date bottles by observing how high the mold line goes up the neck--a method that
has been thoroughly disproved.  Kendricks did great work for the time period, but it is
time to begin looking to research done by archaeologist and more up-to-date
collectors.

Bill



> The only reference to selenium glass I have seen is in an antique
> bottle book:
>
> "The Antique Bottle Collector"  by Grace Kendrick.  1966 Old Time
> Bottle Publishing Co. 611 Lancaster Dr. Salem, Oregon 97301.
>
> I don't know how accurate the information is, but other information
> concerning bottle manufacturing attributes and solarized/amethyst
> glass are accurate.
>
> Kendrick has the dates for Amber (straw-colored) glass at 1914-1930.
> The book says that WWI cut off the main supply for manganese (from
> Germany) and U.S. bottle makers began using selenium to clarify the
> glass.  Apparently when exposed to sunlight, this glass becomes
> solarized to an amber straw color.
>
> I hope this helps.
>
> M. Jay Stottman
> Kentucky Archaeological Survey
> ----- Original Message -----
> From: "Cathy Spude" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, June 03, 2003 5:34 PM
> Subject: dates on selenium-clarified glass
>
>
> HISTarchers:
>
> I'm ready to throw in the towel. I have the great misfortune to be
> writing up a report someone else did the excavation and artifact
> descriptions for. The lab analyst sometimes put down a start date of
> 1914 for selenium-clarified glass and sometimes 1915. While it seems a
> minor point, it appears, these fragments are my terminous post quem in
> a few cases. The lab manual supplied with the report documentation
> does not give me a citation for her date for selenium clarified glass.
> My limited library does not seem to want to yield up much information
> on the subject.
>
> Can anyone give me a solid date (is there such a thing?) and a
> citation? It would be nice to have an ending date, too, if possible. I
> believe its 1934 or 1935 or thereabouts. Again, I have no citations,
> so don't know for sure.
>
> I expect the beginning date has to do with the cut-off of manganese
> from Europe in about 1915, making 1915 a reasonable date.
>
> Oh, and can anyone corroborate my suspicions that it might be pretty
> hard to tell selenium-clarified glass just by looking at it? This
> stuff came from a buried context (not solarized). Should I be
> suspicious?
>
>
>
>   Catherine Holder Spude ¨ Archeologist ¨ Cultural Resources
>   Management ¨
>     National Park Service ? Intermountain Region ¨ 505.988.6831Voice ¨
>                              505.988.6876 Fax
>
>
>  The National Park Service cares for special places saved by the
>  American
>               people so that all may experience our heritage.
>
>
>
> =

Bill Lockhart
New Mexico State University
Alamogordo, NM
(505) 439-3732