3. resin ctd 'paper' is not paper-the reason for using it as a neg is that there is no fiber grain that will intrude into the print--HOW-EVER- the brighteners that are put into it flouresce very strongly under uv, and it may be that with such long exposures the very bright glow of the support(this would be visable under uv only ) is causing the 'bluring'
Are you sure, z-man?

Kentmere describe VC Select as "...The paper is 190 g/mē coated on both sides with 40 g/mē of polyethylene..."

Forte describes its RC range as "...Fortespeed is graded, resin coated (RC), black and white enlarging paper with a neutral
black image tone. Fortespeed papers are manufactured on a medium weight (175 g/m2)
paper base..."

Ilford, Kodak and Agfa spec sheets that I've read all say much the same - that RC is paper that is Resin Coated on both sides, plus other layers, like emulsion, etc.

Sounds like a lot of paper in 190 g/sm to me!