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