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Have you ever wondered what your spectacle frame is made of? Of course not! it’s made of plastic, or more likely these days: metal. But what plastic and what metal?
Unfortunately, the manufacturers are a little reticent when it comes to revealing the nature of their products and there appears to be a wide variety of materials used in today’s frames, some possessing properties one could not even have dreamed about, a couple of decades ago. Anyone who studied chemistry to O Level probably heard of Titanium, somewhere in the depths of the Periodic Table of Elements, but would have been unlikely to know for what purpose it was used. The local Clairvoyant could perhaps have foretold that in the future it would be used in the manufacture of spectacle frames but this piece of (at the time) useless information would have elicited a reply, no more emotional than “Oh really?”
But what sort of materials were used in former times? Metals, notably nickel and gold, have always been around, but what about plastic? What were Horn Rimmed Glasses, popularised by the late Harold Lloyd, of silent cinema fame, made of? Anyone old enough to be familiar with the comic antics of this cinematic genius, will probably have frequently referred to “Horned Rimmed Glasses” even after such items had long been made from plastics. The term was generic for any brown coloured optical appliance. In fact horn was very little used in spectacle production. Before the age of plastics, most spectacles so described were made from turtleshell, normally misnamed “tortoiseshell” and in the trade known by the shorter term “shell”. This beautiful material, provided by the slaughter of gentle creatures from exotic locations, came in colours blond, demi blond, light mottled, dark mottled and dark. Blond was a light gold colour and came from the belly of the turtle. Consequently, there was less of it and it was much more expensive. The dark tortoiseshell came from the larger back of the turtle and though not exactly cheap was considerably less costly, the other colours, pro rata.
Other materials were horn and a substance called casein which was somehow concocted from ingredients including milk. Both were used in the making of horn rimmed glasses. Later of course, plastics appeared on the scene, the most famous of all, being cellulose acetate. Famous? This humble material along with nickel and gold filled were used in the manufacture of frames selected for provision under the National Health Service in 1948. Cellulose acetate frames however were the nation’s favourite choice, the most popular being frame number 524 which later evolved into the 524H/J (high joint). There was a choice of colours, light or dark. The light was a colour called “flesh” and the dark “B/M” (brown mottled). The colour range was later extended. How many millions (or should it be billions?) were produced, who knows?
Cellulose acetate was for many years the first choice material of manufacturers throughout the world. At the same time, cellulose nitrate was also available and had some advantages, but one big disadvantage, it was highly inflammable. Later there was limited use of PMMA, polymethyl methacrylate, sometimes known as “perspex” but generally known in the trade simply as “acrylic”. Another spectacular (no pun intended) addition to the range of materials was a substance known as OPTYL, developed by an Austrian company, Viennaline, later known as Optyl Eyewear. Optyl was a plastic which was suitable for injection moulding, enabling a vast range of wonderful designs to be produced, subject to heavy investment in tools, and a colouring process which produced a vast range of beautiful colours, but this process remains a secret to this day. It was also extremely durable, which pleased the wearers, but was less welcome to the vendors of eyewear.
Perhaps dear reader-with-a-much-higher-boredom-threshold, you will wish to hear about the history of metal frame making. WATCH THIS SPACE.
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