1951 Bowman Mantle PSA 7(OC) on PWCC tonight

[steve B]

Originally Posted by Goudey77

I heard that the old slabs had some issues with their seals. So if you lived in a humid climate the cards could shrink up to %5
If you study paper fibers used in the 1950's you'd understand the risks involved with post war era cardboard.

So all the cards that measure full size were oversize when they were made?

Also- That card is most likely more than 5% small both ways.

The fibers are mostly wood pulp, maybe with some rag content and additives like clay, plus some seizing. Except in the cards that are multiple layers, where the white front surface is either bleached wood fiber, or may have a high rag content, linen, cotton, maybe some silk or wool Plus some seizing.

What are todays cards made of?
The exact same stuff, except that the white paper/cardstock is now the entire card since 1992 for Topps, and earlier for the other companies.
30's cards?
Guess what?
yeah, the same stuff.

Paper shrinkage generally happens soon after the printing process. And it's less normal on things produced by offset lithography.
Stamps which are intaglio printed do have shrinkage immediately after printing under some conditions, which is why the BEP used experimental papers in the 1920's as well as different spacing on some sheets a bit earlier. Then changed to a "dry" printing process in the 50's. (The sheets are printed "wet" to help the paper get forced into the recesses in an engraved plate and then to retain ink. The edges shrunk faster than the center making the spacing and thus perforations uneven. With more force, less wetting was needed. )

[Goudey77]

Steve B, Glad that my sarcasm resulted in some real world information. Thanks for the knowledge drop.

Not so kidding aside does extreme fluctuations in humidity/drying in the air potentially cause warping and or shrinkage in typical card stock?

Let's say even a good old soak job?

Originally Posted by steve B

So all the cards that measure full size were oversize when they were made?

Also- That card is most likely more than 5% small both ways.

The fibers are mostly wood pulp, maybe with some rag content and additives like clay, plus some seizing. Except in the cards that are multiple layers, where the white front surface is either bleached wood fiber, or may have a high rag content, linen, cotton, maybe some silk or wool Plus some seizing.

What are todays cards made of?
The exact same stuff, except that the white paper/cardstock is now the entire card since 1992 for Topps, and earlier for the other companies.
30's cards?
Guess what?
yeah, the same stuff.

Paper shrinkage generally happens soon after the printing process. And it's less normal on things produced by offset lithography.
Stamps which are intaglio printed do have shrinkage immediately after printing under some conditions, which is why the BEP used experimental papers in the 1920's as well as different spacing on some sheets a bit earlier. Then changed to a "dry" printing process in the 50's. (The sheets are printed "wet" to help the paper get forced into the recesses in an engraved plate and then to retain ink. The edges shrunk faster than the center making the spacing and thus perforations uneven. With more force, less wetting was needed. )

[steve B]

Originally Posted by Goudey77

Steve B, Glad that my sarcasm resulted in some real world information. Thanks for the knowledge drop.

Not so kidding aside does extreme fluctuations in humidity/drying in the air potentially cause warping and or shrinkage in typical card stock?

Let's say even a good old soak job?

Warping - Sort of. The non- coated side would expand more because it isn't sealed. Measuring a pretty serious warp and doing a bit of math, if the center is warped up by .61 (measuring a warp similar to my worst by bending a junk common and measuring how high the center is. )
Then the difference in length between the front and back is only about .005 Inches. Or about 1.6% And that's equivalent to the most warped cards I've seen.

Soaking should do that, but what usually happens if you soak and just leave it out is that the fibers expand in a somewhat random way, leaving a wrinkly surface that we'd all recognize as water damage.
Pressing flat to dry usually fixes that, but by forcing the fibers into sort of their original locations - Unless the soak removed too much seizing, or glue from between layers.

Excess humidity would expand a card slightly. I'd have to see about borrowing the moisture content meter from the makerspace woodshop, or buy my own to get some reliable numbers.
The Stamp sheets that they tried different spacing on were about 2 ft across, and they expanded the spacing by 1mm on four rows. (It didn't actually work, probably because the drying was dependent on the ambient temperature and humidity so the sheets shrunk sort of randomly. )
so you can see there wasn't much shrinkage expected in a paper that had a decent rag content.

The card in question is visibly short both ways, even going on a conservative 1/64th of an inch that's roughly 3x what I'd expect from humidity.

I've never tried shrinking a card. If it's very humid and I bake it, maybe. But I'd expect about as much as the warped cards.
Sounds like an experiment that should be done.

[steve B]

Another data point is that I've had a couple boxes of junk cards in the carriage house, which was for a time pretty damp. For maybe 22 years? They aren't warped at all.