Strop not staying flat

[Christian1]

I have 2 strops, Illinois 127 and SRD premium IV. Illinoise 127 was first strop I have had since 2012 I believe. It had a nick or two and I repaired it recently and started using it more. My SRD strop is only sort of flat when I strop with it even if I pull it back really tight. I have put it under flat even surface and then heavy books on top of it twice now to flatten it out. I use to use my hand and rub the strop before using it but after first time I flattened it I stopped doing that thinking it had something to do with making it not flat.

Anyone have a similar problem? never had this happen to Illinoise 127 but it is smaller in width.

Also strop is in same spot as Illinoise, in my bedroom so temperature wise and staying dry wouldn't be a problem I would think. It is just hanging up as well

[Jnatcat]

Leather cupping can happen is the leather gets wet and also depends on how it was cut to make it along with the quality of leather, also depends on the width of the leather, some 3" strops are more prone to cupping due to there width, you can control this to some degree by squeezing the sides in and force the middle to go up or down.

[Christian1]

Will try messing with sides a tad then next time I am stropping. Thanks for info

[Geezer]

You can also wrap the strop around a table leg and pull it back and forth ( shoe shine) to free up the fibers within it; back side to the leg. Worked for me a few times as I got older strops top renew.
~Richard

[JP5]

You can also wrap the strop around a table leg and pull it back and forth ( shoe shine) to free up the fibers within it; back side to the leg. Worked for me a few times as I got older strops top renew.
~Richard

Interesting suggestion Richard.
Not cupping, but I have a strop I made with a slick/firm surface (got scrap leather from bridle shop). If I ever did this, wouldn't it cause the leather to wrinkle or break up on the surface? Thanks

[Geezer]

If tour strop is supple, no harm will come of it. I have used it in a partial bend to begin the time consuming rehab of old dry strops where I had to use one finger dipped in neetsfoot oil to rub in about 2 square inches of hide per dip.
~Richard