A patient asked me today why her lenses were called CR‑39, and it reminded me of the 1940s origin story — who here can name the company behind it and what the “39” refers to? I share this tidbit in rehab sessions because understanding materials empowers folks to choose lighter, safer, glare-friendlier options that support their reading goals.
Columbia Resin ‘No. 39’ from PPG’s Columbia Southern Chemical — 39 was the 39th formula that finally worked. I tell patients it’s lighter than glass for comfort, but if safety’s the priority I steer to poly or Trivex — the 39th recipe wasn’t the toughest.
And fun add-on: the monomer is ‘allyl diglycol carbonate,’ and it first hit ophthalmics via Armorlite around ’47 after PPG’s WWII fuel‑tank work in the 1940s. My patient‑friendly tip is a quick dye dip demo — CR‑39 soaks color faster than poly for glare control, but I do warn it needs a hard coat or it scuffs. Do you ever call out its high Abbe (about 58) as the comfort angle?