I’m revisiting my Lansing Company Inc catalogues from 1951-1961. I thought they might help with indentifying the types of plastics used. I immediately hit a problem; they are describing as bakelite many buttons that test negative to simichrome polish, are light weight and also include white examples! Perhaps they are a phenolic plastic, but they can’t be bakelite. Bakelite is weighty, turns simichrome from pink to yellow, and white oxidises quickly to yellow.
Polyester (or not?)
These below were labelled as polyester in my catalogues: they all have a glistening, oily, slightly translucent appearance. As light plays on the surface, the colour varies in shade.
This site explains how polyester buttons are made. http://www.madehow.com/Volume-2/Button.html
According to https://www.popoptiq.com/types-of-buttons
“Polyester is a very common material for buttons because it is a type of plastic that makes it perfect for all types of buttons. Polyester is inexpensive, looks great, and can be dyed a variety of colors. Sometimes, red carbonate is added to polyester to make buttons that have the pearlescent sheen of shell buttons, but the truth is, polyester buttons offer so many options that it is all but impossible not to find something you love when you choose buttons made of this material.
Polyester buttons make it easy to button and unbutton a dress or blouse, and if you choose polyester buttons, they can even mimic other button materials, which means you are always guaranteed to get what you love without paying a fortune. Polyester buttons can be made to look like wood, pearl, or any other type of button, thanks to their versatility and the fact that they come in so many designs and colors.
For most non-professionals, therefore, it is virtually impossible to look at a button and determine whether it is made of polyester, wood, or any other type of button-making material. Most polyester buttons vary greatly when it comes to shading, luster, and brightness, so they can be light or dark, formal or casual, large or small, meaning you are always guaranteed to get something spectacular in the end.”
I confess that these above buttons look like many that were sold on Leda branded cards, which I thought were acrylic (Lucite). It’s a tricky business identifying plastics as they can mimic other substances and each other. According to https://www.sbs-zipper.com/blog/resin-buttons-vs-plastic-buttons-understanding-the-differences/ the term ”polyester” most commonly refers to a plastic subtype called polyethylene terephthalate (PET). Wikipedia tells me that polyesters are a family of plastics that can be both themosetting or thermoplastic, which doesn’t help me with hot needle testing, although my polyester buttons had no smell with hot water testing and were resistant to a hot needle for what its worth!
According to an article in the Pioneer Button Club, July 2018, polyester has taken over from acrylics for high end buttons being produced today. The author also bemoaned the lack f a “foolproof, non-destructive way to tell acrylic from polyester 100% of the time.