Un-curling negatives

Hello,
so I'm in the middle of a printing session, and I just wrestled with some old foma 100, which was a huge pain in the butt. It is so curled that it literaly goes in a complete circle when I take it out of the archival holder. I have had this problem with 35mm before, and it just fixed itself by sitting in the holder for a week or so. It's going on 3 weeks since I processed the film, and it still will not stay flat. What can i do about this?
-Austin

Place the negs in archival clear sleeves, then place a between two phone books. Some may cringe, but I've been doing this with transparencies that occasionally curl for 30-odd years. The warmth from a lightbox can also cause curling.

Nudge: It's analogue (US) or analog (AU)

I find that fomapan 400 no longer curls like it did a year or so ago, but I would put the sleeves under weight, just like FB prints, for a few days and it would straighten out,
Richard

The Foma 120 I have curls pretty bad.
I reverse roll it quite tightly then keep rolled with a clothes pin then leave it in the cabinet for about a week, it really takes the curl out.