Cardboard storage boxes - problems with discoloring?

I am in the process of re-organizing my collection and as I was checking my 600 and 800 count cardboard storage boxes of 60's baseball cards (stored just in the boxes without any sleeves) , I noticed that the outside of three of the boxes had discolored. What I mean is that instead of being a pristine white, they had almost picked up a dingier, grayish look. Here's the old box (left) next to a new box (right):


I have dozens of storage boxes that I've purchased at different times through the years and these were the only ones where I noticed a different outside color. When I looked at the cards inside, they also seemed dingier and maybe a little yellowed. I don't know if that's what 40 year-old cards normally look like, so I can't be sure if the boxes changed them. What do you think? Here's a Tiant that was in the boxes:

I purchased these three storage boxes in the early 90's and they have been stored in brand new, completely dry Rubbermaid plastic tubs in a dry closet ever since, so I ruled out any environmental effect. I got to thinking and the only thing I could come up with was maybe these boxes that were made during the sportscard boom of the early 90's had more acid in them than the boxes do nowadays. Does that sound possible to anyone? Do you think that would affect the cards?
In any case, it scared the heck out of me and I ran to the local card shop and bought new storage boxes and a couple thousand penny sleeves. I am going through and putting the cards in the penny sleeves in the new storage boxes. I am hoping this will be a good long-term storage solution. I know everyone on these boards has a lot of knowledge and experience about vintage card storage (I've read many good storage topics in the past), so I wanted to get your thoughts.
Thanks


I have dozens of storage boxes that I've purchased at different times through the years and these were the only ones where I noticed a different outside color. When I looked at the cards inside, they also seemed dingier and maybe a little yellowed. I don't know if that's what 40 year-old cards normally look like, so I can't be sure if the boxes changed them. What do you think? Here's a Tiant that was in the boxes:

I purchased these three storage boxes in the early 90's and they have been stored in brand new, completely dry Rubbermaid plastic tubs in a dry closet ever since, so I ruled out any environmental effect. I got to thinking and the only thing I could come up with was maybe these boxes that were made during the sportscard boom of the early 90's had more acid in them than the boxes do nowadays. Does that sound possible to anyone? Do you think that would affect the cards?
In any case, it scared the heck out of me and I ran to the local card shop and bought new storage boxes and a couple thousand penny sleeves. I am going through and putting the cards in the penny sleeves in the new storage boxes. I am hoping this will be a good long-term storage solution. I know everyone on these boards has a lot of knowledge and experience about vintage card storage (I've read many good storage topics in the past), so I wanted to get your thoughts.
Thanks
"It's not so important who starts the game but who finishes it."
- John Wooden
- John Wooden
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WTB: 2001 Leaf Rookies & Stars Longevity: Ryan Jensen #/25
- John Wooden
1996 Select Certified Mirror Gold Ozzie Smith
2006 Bowman Chrome Orange Refractor Chris Carpenter
You can read about "foxing" via google.
The RubberMaid boxes seem to work pretty well.
Many closets are much more humid than the houses they are in.
The stamp guys use heat lamps to help mitigate the problem.
Cards that are valuable/liked should be in penny-savers.
I ended up giving most of the collection away, but the stuff that I did keep got re-boxed in fresh new boxes. I even wrote the date the boxes were purchased on the boxes.
So far, I haven't noticed any problems with the re-boxed cards, but time will tell.
Sleeving eveything is a good idea. It keeps the edges and corners nicer (if you get a big enough box), and it also keeps the newer glossy cards from self-gluing themselves to each other.
WTB: 2001 Leaf Rookies & Stars Longevity: Ryan Jensen #/25
It's more or less common sense, but sometimes easier to say than to fully achieve - dark, dry and cool (stable) temperature is what you want. This and as little exposure to air as possible.
As an example, with comics, still the most famous high-grade collection to come to light are the Mile High books - found in the dry storage room in the basement of a Denver home - sitting in stacks some ten feet high that had been started in the '30s-'40's.
Through sheer luck, the books were away from any light source, rarely disturbed, were spared vermin and the ambient temp of the climate was perfect in preserving their inherently acidic pulp paper.
One other interesting thing noted by the ultimate buyers of the collection, was that the top of the stacks had books with the most browning to the edges (air could get in) - those at the bottom were fully compressed, and snow-white in quality as the day they were printed. HTH!