| The early glass makers were really
not that bothered about the quality of thier glass,the iron
oxide in the sand they used produced a light green glass
which ideally suited the wine bottles they were producing.But
as demand for goods packaged in glass increased manufacturers
began to demand darker colours(often to disguise impurities in
the contents,ie sediment in beer or wine).To accomodate these
wishes the makers added more iron oxide to the melt to
produce dark green glass.Even larger ammounts made brown glass(often
used for early medicines,poisons).Even darker brown(or black
glass)was produced by adding small ammounts of coal or charcoal
as well as the iron oxide.Blue glass often used for later
poisons and medicines was produced by adding cobalt(dark
blue)or copper oxide(lighter blue).It is likely that the
copper oxide was of most use to the glassmaker as by varying
both the ammount used and the temperature of the melt blue,light
red or emerald green glass could be produced.Milk glass(white)
was popular (and still is) for creams and other cosmetics and
was made by adding either tin or zinc oxide to
the melt.Small ammounts of either sulpher,silver or chromium
produced varying shades of yellow(also popular for cosmetics/perfumes.Ruby
or red glass was made by adding 1oz of gold to 60lbs of
glass.Consequently it is very rare to find a commercial bottle
in ruby glass.(due to the expense).These days ruby glass is made
by adding selenium to the melt.Clear glass became more
popular from the start of the 20th centuary and was produced
by adding manganese.(an added benefit/hindrance to this
is that early clear glass can often be subjected to ultra violet
light to produce a light purple colour bottle/or cooked to make
a fairly common bottle a bargain(expensive buy) for the novice
collector,of which I am one,I havnt bought a purple bottle yet
though.From the 1920s on selenium replaced manganese,these
bottles are unaffected by UV light.Though in very VERY hot climates
they have been known to turn a very pale yellow if the glass
contains large ammounts of selenium. |
