Warped Sealed Sheets

I am assuming that warped sealed sheets are due to being stored in highly humid conditions, correct? What percent less is a warped sealed sheet worth vs one that lays flat?

American-made LPs used to warp because of the shrink-wrap in which they were encased, rather than humidity. Are you sure this isn't hapoening here?

I would be more worried about the humidity aspect of your post. It is very possible that the humidity has caused the sheets to stick together, or stick to the plastic that they are sealed in. If the gum has become stuck, or even disturbed, then this would have a great effect on value. If they are simply warped, with no impact on the gum, as long as they are not creased, or as long as the sheets aren't falling apart, I would think a little warping would have little impact.

I don't know if tight shrinkwrap causes warping or a high humidity environment does.

What sort of sealing wrapper is around the stamps? Is it tight to he borders of the sheets?
What happens to one of these warped sheets when it is removed from its sealed environment? Does it stay curled or warped?

Photo?

jleb1979: The listing in the link below is an example of what I mean by a warped sealed sheet.

https://www.ebay.com/itm/Marilyn-Mo...AOSwUwRfWsdt

What caused this sheet to warp? Should a sheet like this be worth less to most people than one that is also sealed but not warped?

I revert to my suggestion that the shrink-wrapping is the cause of the problem. Are you looking at these or similar to collect or use for postage? If the former, they should flatten. If the latter, it doesn't matter.

Seeing the link to the Marilyn Monroe pane reminded me of another danger of shrink-wrap. I had a USPS Marilyn Monroe "Stamp Folio" for years, still in the shrink-wrap. When I eventually decided to remove the shrink-wrap, it was already too late. The shrink-wrap had adhered to the folder and could not be removed without damage.

Hmmmm... I have NEVER had damage occur to my still-sealed US stamps... then again, they are all stored in flat locations.

I wouldn't think humidity would effect the shrink-wrap itself, UNLESS too much heat was applied when it was "installed" and the plastic has any sort of hole.

I used to have to shrink-wrap things when I worked at a print/copy shop YEARS ago, and too much heat could indeed make the plastic too tight, causing the paper inside to "warp"/buckle. If I remember correctly, that is the type of wrap the USPS first used when they switched to pre-packed stamps.

Today, they seem to use a simpler style of wrap, one that is simply a sheet with heat applied just to seal it.

If there are no "air holes", then humidity shouldn't reach the stamps or cardboard inside. If there ARE holes, then you may get moisture BUT I really don't think it will cause issues with modern self-stick stamps.

Just my 2-cents

I have seen examples of US stamps that were plastic wrapped where in places the plastic left behind a residue on the stamps (you could see it by holding the stamps at an angle to a light and you would get more reflective patches). This was 20 or 25 years ago. edited to add the places where the residue was left behind was here the plastic was lightly stuck to the stamps.

Thank you for your educational comments. Here are some additional examples of warped sealed sheets:

https://www.ebay.com/itm/CLASSIC-AM...114180155143

https://www.ebay.com/itm/T-039-US-3...163978952461


Can these sheets be flattened in a dry environment or are they permanently warped and best for postage only? Not interested in purchasing above listings, just examples only.

Such packaging is not archival nor for long term storage. I have even seen that on the back of some packaging. That is the bad news. The good news is if the sheets are removed from the packaging and place into a mint sheet file of most any sort, they will flatten. The exception is if the shrinkage has caused paper buckling in the perforations.

Parcelpostguy: Thank you for the explanation.