I remembered that Piccolite resins are clear so they're probably not derived from pine stumps.
I called the distributor. The PICCO resins they sell now are polystyrene. The distrubutor thought that they might have made PICCO resins from coal tar in the distant past.
Polystyrene was around in 1960 and maybe 1950 but I don't think it was around as a commercial material before WWII.
So PICCO resins may have been made from coal tar, not pine stumps, in the distant past.
He told me they're still using the original PICCO factory in Ohio. Anyway tank cars of coal tar might have been delivered to PICCO.
