I have used Moir's window glass formula with great success at my 19th century Missouri sites. It is important to note that it only works for 19th century glass, and of course only denotes a date of manufacture of the glass itself (not necessarily the structure). It is also useful to only measure glass fragments that are at least 1" in one dimension, since smaller pieces are harder to distinguish from panel bottle fragments, etc. Also, it is good to take 3 different thickness measurements for each piece of glass, and use the mean thickness for the formula. As noted earlier in this discussion, buildings that have been in existence for a long period will certainly have windows replaced in different time periods, so that has to be factored in.

I wouldn't use this method of dating window glass at my only means of establishing a chronology at a site, but when used in combination with other datable artifact types, it can be very useful.

Ann Raab, RPA
PhD Candidate, University of Kansas




________________________________
From: Conrad Bladey <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, February 19, 2010 1:58:33 PM
Subject: Re: Plate Glass references

Perhaps a material where size and shape and wear is so important. Of course the original soil matrix as well. Windows generally crack into relativly large pieces. I never dealt with large pieces however the smaller ones were never worn down most likely because with any preasure they simply went deeper into the matrix of the soil.

Patrick Martin wrote:

> In the published version of my thesis (1985   The Mill Creek Site and  Pattern Recognition in Historical Archaeology.  Mackinac Island State  Park Commission, Archaeological Completion Report Series, Number 10,  265 pp.,  Mackinac Island, Michigan.) I analyzed about 15,000 flat  glass fragments from three nineteenth century building ruins based on  thickness distributions and Moir's formulaic dating approach.   I got  different results than Moir did, but some interesting patterns.  You  might consider having a look for comparative purposes, at least.
> PEM
> 
> -----Original Message-----
> 
>>> From: HISTORICAL ARCHAEOLOGY [mailto:[log in to unmask]] On Behalf Of
>>> Benjamin Carter
>>> Sent: Friday, February 19, 2010 9:09 AM
>>> To: [log in to unmask]
>>> Subject: Plate Glass references
>>> 
>>> All,
>>> 
>>> I am having a bit of trouble finding references for the dating of  plate
>>> glass.
>>> 
>>> There are, of course, far too many resources for bottle and table  glass,
>>> 
>>> but I haven't had much luck finding out any details about plate  glass.
>>> 
>>> I have mostly plate glass with a bluish cast, which I assume is soda
>>> glass. But, I also have, from the same contexts, some extremely  clear plate
>>> glass. Why are these different? I assume that 'decolorizing' agents  were use
>>> for the clear glass. Is there a time when this began. The site is  fairly
>>> well dated- 1790s-1811. Would a change in glass types
>>> 
>>> have happened at this time? Or, is it likely that the clear glass is
>>> intrusive. Many of my contexts are fairly close to the surface.
>>> 
>>> Cheers,
>>> Ben Carter
>>> 
>>> 
>>> 
>> 
> 
> Patrick E. Martin
> Professor of Archaeology and Chair
> Department of Social Sciences
> Michigan Technological University
> Houghton, MI  49931
> phone 906-487-2070,email [log in to unmask]
> www.industrialarchaeology.net
>