Many of the Leda buttons I received in my last batch were clearly a different plastic to the casein types so commonly used by general Plastics and G.Herring in the 1940s-1950s. I don’t often ‘hot needle’ test my buttons due to the damage done to the buttons, but I decided to ‘sacrifice’ a spare button to science. Using http://www.thebuttonmonger.com/content/button_identifying.pdf as a reference, and other websites, I decided they were polymethyl metyacrylate, better known by the trade names of Lucite, Perspex, Plexiglas, Acrylite, and others, but more easily referred to just as ‘acrylic’.
Developed in the 1920s and first marketed in the 1930s by several companies, it would be widely used during WW2 for airplane turrets, windscreen and the like. Du Pont had licensed this new product to jewellery manufacturers early on, which is why the name Lucite (their trade name) is used generically for acrylic buttons. It proved a valuable and flexible product, highly suitable for the manufacture of jewellery, beads, buttons and many other products. Although Naturally clear, it could be coloured, clear, translucent or opaque. It was lighter than glass, strong, and did not yellow with age. Its peak popularity was post WW2 into the 1960s, although it is still used. Vintage plastics with embedded glitter or other objects are usually acrylic. My buttons are the ‘Moonstone’ acrylic variety, with a slightly greasy feel and a glossy, glowing, variable colour tone.