Casein
Casein plastics were introduced at
the beginning of the 20th century, their starting
material being the protein in cows milk,
precipitated by the action of the enzyme rennin.
Although casein is readily moulded to shape under
moderate heat and pressure, it does not produce a
stable material for manufacture until it has
become hardened by soaking in formalin (5%
solution of formaldehyde in water) for a long
period. Unfortunately, this causes much
distortion so casein plastics are almost always
produced by machining stock material such as
sheet, rod, tube or buttton blanks (small discs).
After machining, casein may be polished either
mechanically with abrasives or chemically with a
'dip polish'.
The material readily takes a surface dye, so
coloured items can be quickly made from pale
coloured stock items. This was especially
important for the button trade which was the
principal consumer of casein plastics.
As well as buttons and buckles, casein was also
used for knitting pins, fountain pen and
propelling pencil barrels, dressing table ware
and a host of other items.
For a more
detailed account click here.
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