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Originally Posted by CMIZ5290
Michael- I'm a bit confused. On cards with definite color variations, if they were in the presence of chemicals, wouldn't the borders of the card be off as well? Also, if the color was altered by the sun, wouldn't there be discoloration or toning on the borders?
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The inks were and are colored by a variety of pigments. Some are more stable than others.
A chemical that changes the color might only affect one of the colors. That would depend on the chemistry of the chemical and the pigment.
Other chemicals could affect the carrier, usually some sort of oil or grease with lithography inks. Some oils like linseed oil eventually harden, others don't. Modern environmentally friendly inks are often based on vegetable oil and can be smudged or removed in normal handling if your skin isn't especially dry. Sports illustrated used inks like that for a while.
I'm not really up on the exact pigments for most colors, but know a little about a few of them.
Most black ink is colored with carbon, either carbonblack or lampblack. (A fine distinction of the process used to get the carbon pigment. And usually one that doesn't matter. ) Carbon won't fade, and isn't affected by most chemicals.
Reds are sometimes done with Cochineal. And while it makes a nice bright red dye that resists fading from soap, it will fade with exposure to light.
Many other colors don't fade.
That's why I bought a small lot of cards with no bright red, but a known history of light exposure of around 40 years. Unfortunately a few other cards from the same batch have been slabbed as missing colors. The good look I've had at mine is to me inconclusive. One shows gloss where the bright red should be, the other doesn't.
On both, none of the other colors have faded much if at all.
The borders on T206 fronts won't be affected by light. Backs exposed to light might be affected a bit, but I don't have any examples. The good news is that the cardstock is probably not particularly acidic.
A lot of lithography stock is coated on one or both sides. The fronts of T206s are coated stock. Probably a clay based glaze. The coating makes the inks appear a bit brighter and helps them adhere better to the surface without getting into the paper itself. The backs are uncoated. So stock that's more porous than usual will absorb more ink. I should also make clear that the ink is very thick, and won't bleed through. The depth it penetrates porous uncoated stock is very small. Maybe a layer or two of fibers.
Many T206s under a lot of magnification will show a bit of fine cracking to the glaze coating on the front.
And, over three years the exact cardstock and inks may have changed.
As Kevin pointed out the press operators have formulas they follow. But they don't always follow them as precisely as they should. Other things during printing can also change how a color looks. The amount of ink put onto the plate can be changed, as can the amount of water. So a color can be overinked or underinked, making it darker or lghter. Or printed drier leading to small areas being filled like the drame lines on Piedmonts, or printed wet, which can prevent some areas from printing at all. Dry prints are pretty common on T206 backs, wet prints aren't common at all. I can't recall seeing one, but there's probably a few.
Steve B