• Casein: high polish on front

    Casein identification guide: casein is a thermoset semi-synthetic polymer made from milk, hardened in formaldehyde

    8. Takes a high polish, but the back may be unpolished or less polished, helping to differentiate from Bakelite, which is tumble polished on all sides.

    source: Button Materials A-Z: Identification Guide
    by Jocelyn Howells

    Button Specs