Curled Stamps

Recently I got a box with mint and Cto stamps, some of them would be useful, but they`re curled. They were kept near a stove (probably that`s why?). What can be done with them, without harming the gum of the mints?
Thanks

Not much. I happily soak my CTOs. I would soak the mint stamps too depending how now badly curled up they are. Trying to straighten them by force if they are badly curled will also damage the stamp in the long run.

Wadmalatz
For sheets that are curled a little I put them under a pile of catalogue for 1 day. They seem to become more flat. With stamps I never tried.

What are the best condition so stamps don't bend, curve or curl? For me some countries are worst than other for certain era. I think my Poland collection is the worst for that. Even in my album in his mount a polish sheet from the 60' 70' 80' will not stay flat. My stamps are in the basement but I don't think it's too humid, certainly not in winter the furnace heat dry the place or maybe it's to dry...

Depending on the stamps, it think's there's a few factors that can cause stamps to curl. Of course humidity, but can the gum of the stamp contract with age? I've had this problem with sheets and partial sheets of German inflation issues that would curl up to the point they were in the shapes of tubes. No manner of pressing them flat with objects over any period of time worked. I have some Romanian cto stamps in sheets that have done the same.

My `problem` stamps are Romanian, Afghan & Emirates (esp. Sharjah), from the `60s,`70s. Only a few mint Polish stamps I have, but with Cehoslovakian mint stamps I have a lot of trouble. Thanks everybody, I give an 1-2 day try & press, then comes soaking.:(

I am not sure, I have not tried this myself, but for dried stamps would a sweat box, perhaps modified with less moisture) give the curled stamps back their moisture content so when flattened and pressed they would stay flat?

just place them in between two albums are two heavy books, then will straighten automatically.

warm wishes.