What are Polyester based gel types?

T35 – Akzo Nobel
Polyester gel coats are very porous materials. Each pore creates a relatively sharp transition with the surface, this sharp edge is subjected to increased photo-initiation. These holes are also collectors of micro-debris resulting in increased chemical reaction & degradation. Obviously keeping this to a minimum by polishing is essential.

Most gliders produced since the late eighties have been finished only in Scheufler T35. 
Before that date Grob, DG, and Glasflugel had used Schwabelack while the others used T35 Vorgellack and still do. Schwabelack is out of production.