Roller Compression

Humidity, heat or cold will make the rollers shrink or swell. Dick G.

In the days when Letterpress was king you placed your order with the roller companies and specified “Summer” or “Winter” use——they then formulated the composition
to fit the season and guess what——you RARELY had a
problem if you took care of the rollers by cleaning them
(including the sides) very carefully after each use and
storing them in a wooden box if they weren’t going to be
used for an extended period of time. There is also NO
need to “tape the rails” if the rollers were cast to the
correct diameter of the trucks.

Composition rollers would print really well, but they didn’t seem to last long. The other problem was mice, i still have a pair that a mouse ate clean down to the core . Now i stick to the softest rubber rollers i can get. Dick G.

On the other hand, in the old days the tracks were less worn than now, and photopolymer plates were not used, and they require a much lighter roller contact than do metal type and plates. And today any beginner online can be assumed to use photopolymer plates, unless otherwise indicated.
The original post says nothing about comp rollers, and the only manufacturer of comp left in the US does not recommend comp with photopolymer. Rubber may shrink and harden with age, but not quickly.
The point is that what was correct before photopolymer is not necessarily correct today because of wear, and the specific requirements of photpolymer.
I would check the rollers with a roller-setting gauge to see if anything has changed. Many tapes can compress.

Thanks, guys!

The shop is pretty humid these days, so that’s probably the cause.

I’m running rubber rollers on photopolymer and the rails are quite worn…

Humidity will not affect the diameter of a rubber roller. The previous posts assumed compostion, which does swell or shrink to changes of humidity.
Humidity can also affect photpolymer durometer.