Drain off the excess water, blot, and then place the plant and paper in a single-folded newspaper sheet. Stack with blotter sections as for land plants, and remember to change the blotter newspapers frequently. Any plant material but not flowers that has become wrinkled during collection or temporary storage can be revived by soaking in water before pressing. For example, fern fronds which begin to curl around the edges will flatten in water. If the drying time was too long or if not enough pressure was applied even though the stems were flat, the leaves will wrinkle.
Some specimens can have brown discolourations.
This is because rot has begun because the blotter newspaper sections were not changed often enough. Sometimes your plant material will stick to its paper. It does so because it is not yet completely dry. Sometimes colours fade. The faster the drying, the less the fading.