The best old glass like that found in religious panels was blown as a
cylinder, with additional colours added or with colour flashed on to
it - red was made with gold so only a thin layer was applied to save
money. Modern red is based on selenium but lacks the rich, ruby tone.
Flashing also allowed selective removal of the colour by cutting or
etching. (Fluoric acid - nasty).
The cylinder was opened to a tube, slit and laid flat. Even with
rolling, thickness was highly variable. Leadlighting was developed to
make large windows out of the small pieces that were available, as
large panels of glass were difficult and expensive. There would also
be a tendency to place the thickest edge of a bottom piece towards
the base as the large edge came was better able to accommodate the
extra thickness. If someone were to measure the glass in the window
by looking only at the bottom pieces - which might make sense to a
'scientist' who had never actually faced the decisions of those who
cut, grind, solder and putty, then they may well find that those
pieces were thicker at the bottom than the top.
I suspect that no-one who has ever had to cut and shape cathedral
glass has EVER mistaken it for any kind of liquid, fast, slow or
bloody glacial.
Andrew Fildes
afildes@xxxxxxxxxxxxx
On 02/05/2006, at 8:04 PM, Terry and Tracey wrote:
> I've often heard that glass is a liquid. The reason the old glass
> is fatter
> at the bottom is that is the way way it was poured in the olden
> days. It was
> easier than trying to make the glass flat. Times have since changed.
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|