Red to Orange in c. 1910 T and E cards.

[bnorth]

Cool thread. Was told years ago this is why there are orange T206 Cobb cards. As soon as they started selling at a premium magically several showed up.

[G1911]

Here's another kind of color change that occurs naturally, without need for a card doctor.

These are C52's, which does not have a stock variation. The card on the left bears evidence of having been affixed to something, but appears normal, with the light cream stock and clearly black ink. The card in the middle is heavily toned, its back ink starting to lighten, but still mostly black. The card on the right is heavily toned, and its back is no longer black, but an almost teal green.

The cards in middle and right were from a very old (possibly original) outside the hobby collection, stored in an album for at least several decades until I acquired it, where cards were slotted in between two sides of thick paper. These aren't rare teal backs or a different stock, it's the back changing tone and ink color from its very long contact with the album pages. This is most commonly seen on Canadian cards, where this particular type of album storage was clearly more popular, but it is encountered on T cards as well. I hope Steve can explain why exactly this is so, because I can only speculate.

If an odd colored back is also toned, beware. It's almost never actually a rare printing error.

[steve B]

There's a lot going on there. A few different things all at once.

The typical scrapbook or album years ago had pages that weren't acid free if anything they were pretty acidic.
Products of the fibers in the wood pulp breaking down over time. Some huge percentage of books produced around the 1890's -1920's are mostly doomed if they don't get deacidified. So much so that LOC tried building a machine to deacidify books in bulk.
That acid makes the paper turn brown and brittle. It can and will transfer to paper that's held against it, even staining acid free paper.
I don't know for sure if those cards are also acidic, or if that's just staining from the acidic album pages. It could be either. The T220 and T218 cardstock is actually pretty good, I haven't looked at it super closely, but some older paper - pre optical whiteners had a high rag content. So It's got fewer (Or no) wood fibers, instead having flax, wool, cotton and maybe silk. Once bleached, it's hard to tell. I believe at least some T card cardstock is at least as acid free as the stuff you can get in the craft store.

The second thing is related to the third.

The inks could be darker or lighter depending on how much colorant was used. What the hardening agent/carrier is affects it too.
Black was usually carbon, which won't fade, and isn't really probe to chemical changes either. But it could also be a chemical dye, and those are changeable. My kid chemistry set had a way to make black ink, then to change that ink to blue. And the cool part was also being able to change it back to black.
So it may be the acid in the paper changing the ink
OR
It may be the ink being slightly translucent, and the color you "see" is the paper color darkened by the overlaid ink. Everyone will see this differently. I see the right one as a gray with maybe a bit of overtones of blue or yellow. If you're seeing teal, it may be that you are better at seeing yellow shades, and that the ink I see as Black/gray is actually a very dark blue. Mixed with a bit of enhanced yellow... might = teal. So we could see a color totally differently, and both be "right" (And yes, that's effin confusing!)

And there's a good lead in to the third possibility.
Since we all perceive color differently, that color difference could be from the "black" being seen against a yellowish background.
That sort of thing is the underlying thing in modern cmyk printing, the four colors mix in perception to produce ALL colors.
I was going to write up a thing about this for more modern cards, where two of the same card have slightly different shades in the sky it's often a slight registration problem.

All this could be put to rest by identifying the ink composition etc. But it would take access to some really involved equipment.

[G1911]

Originally Posted by steve B

There's a lot going on there. A few different things all at once.

The typical scrapbook or album years ago had pages that weren't acid free if anything they were pretty acidic.
Products of the fibers in the wood pulp breaking down over time. Some huge percentage of books produced around the 1890's -1920's are mostly doomed if they don't get deacidified. So much so that LOC tried building a machine to deacidify books in bulk.
That acid makes the paper turn brown and brittle. It can and will transfer to paper that's held against it, even staining acid free paper.
I don't know for sure if those cards are also acidic, or if that's just staining from the acidic album pages. It could be either. The T220 and T218 cardstock is actually pretty good, I haven't looked at it super closely, but some older paper - pre optical whiteners had a high rag content. So It's got fewer (Or no) wood fibers, instead having flax, wool, cotton and maybe silk. Once bleached, it's hard to tell. I believe at least some T card cardstock is at least as acid free as the stuff you can get in the craft store.

The second thing is related to the third.

The inks could be darker or lighter depending on how much colorant was used. What the hardening agent/carrier is affects it too.
Black was usually carbon, which won't fade, and isn't really probe to chemical changes either. But it could also be a chemical dye, and those are changeable. My kid chemistry set had a way to make black ink, then to change that ink to blue. And the cool part was also being able to change it back to black.
So it may be the acid in the paper changing the ink
OR
It may be the ink being slightly translucent, and the color you "see" is the paper color darkened by the overlaid ink. Everyone will see this differently. I see the right one as a gray with maybe a bit of overtones of blue or yellow. If you're seeing teal, it may be that you are better at seeing yellow shades, and that the ink I see as Black/gray is actually a very dark blue. Mixed with a bit of enhanced yellow... might = teal. So we could see a color totally differently, and both be "right" (And yes, that's effin confusing!)

And there's a good lead in to the third possibility.
Since we all perceive color differently, that color difference could be from the "black" being seen against a yellowish background.
That sort of thing is the underlying thing in modern cmyk printing, the four colors mix in perception to produce ALL colors.
I was going to write up a thing about this for more modern cards, where two of the same card have slightly different shades in the sky it's often a slight registration problem.

All this could be put to rest by identifying the ink composition etc. But it would take access to some really involved equipment.

Thank you for this, great stuff. I would suspect the T218 and T220 card stock is not acidic itself, just from handling tons of them and from noting which ones have such problems and how they were stored when acquired from finds. Thank you for sharing