Flattening a rubber board?

[agp]

I got a Japanese rubber board and it's starting to arch in the center... not sure why. Does anyone know how to flatten it?

 

[M1k3]

Warped or worn?

 

[SeattleBen]

Might try and press with more weight and then you’ve got to store those boards flat.

 

[McMan]

Some can go in the oven at very low temp--Hasagawa (I think) has this in their instructions. Someone brought it up a week or two ago in a thread where there was a recommendation for the brown Hasagawa.