Debbie Rotman wrote:
>
> Seeking the wisdom of experienced HAs, I have the following queries:
> 1)  What is the correct term for a textured surface on a glass vessel?
> Textures, such as the "orange peel" on the bottom of some bottles, are
> created by the mold, but is it embossing?
>
> 2)  Is patination on glass shards temporally sensitive?  Or is it strictly a
> matter of post-depositional conditions?
>
> 3)  What attributes of stoneware date to the first half of the nineteenth
> century?  Any suggestions for sources on nineteenth-century
> stoneware?
>
> Much appreciated,
> Debbie Rotman, Rachel Mancini & Aaron Smith
> Ball State University
 
 
Dear Debbie, Rachel and Aaron....
I am responding to your question regarding the patination of glass....do
you mean the exfoliation (irredescence?) of the outer layers of the
glass?  If so, this is caused by many things, including the composition
of the glass (in particular the modifier being either sodium or
potassium), AND the burial environment- including but not limited to
moisture, temperature, pH!!, ions present, physical abrasion, pollutants
etc.  All these factors in combination effect the stability of glass in
the ground and post-excavation.  In addition, pH plays a particularly
important role, as glass which is found in very acidic or very basic
environments (esp below above pH 9) will be more susceptible to decay.
Above pH 9 the silica bonds in the glass are broken, leaving it open to
futher degredation.  If you would more on this subject, or references to
articles please feel free to contact me.
 
Lisa Young
Archaeological Conservator
 
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Lisa A. Young, President
Alexandria Conservation Services, Ltd.
 
 Phone:  703-317-8400
   Fax:  703-317-1148
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