New & old 1991 Topps variations scarcity including backs (personal experience).

[Pat R]

Hi Steve,

Yeah there is a lot of differences especially under a black light. I haven't figured out a good way to capture some of them in a photo under black light.
The glow backs that were printed late after the corrections have a different look. I don't know if it's different fibers in the paper but they have almost a "dirty" speckled look.

My replies in blue.

Originally Posted by steve B

Don't forget the other glow backs, which are a very dark red under UV.
From the smallish sample size I have, they're not at all common.
I'm not sure what you're referring to here do you have an image you can post?
There's a few other UV oddities, but so few I can't rule out something post production.
I don't know if this has anything to do with what you're talking about but I've noticed the gum can have an effect on the backs under black light several cards in.

Cardstock that either reacts or reflects UV, showing sort of blue white ish, or with white fibers. Only a couple of each, and they could be fiber transfer from a reactive paper.
There's definitely different cardboards found in the same packs usually it's only two sheet codes either the A & B non bold logos or E & F sheets. If it's a full box all the packs in the box follow the pattern.
A glosscoat that reacts green under UV. Only one so far, but I haven't spent hours doing the fronts with the blacklight.

I come across a few cards that have a glossier feel than the rest I'll have to check one under black light next time. I've also had a couple of boxes that had several cards that have a matte finish (all with the same sheet code or codes) with almost no gloss or what seems like no gloss at all.