Ah, I see, thanks.
We keep whatever medium we're using wrapped in damp cloth and spray it from time to time. Traditionally the rushes or other straw were thrown into a water source - pond, puddle, stream ... that was probably easier in wet Britain than in the desert :-)
That reminds me (coming back to sewing, loosely) that a friend who's regarded as The Authority on mediaeval fabrics including spinning and weving says that spinners of long ago developed a notch in their front teeth where they drew the spun linen through their spit. She doesn't do that, she keeps a tiny pot of water on her distaff but I like the image :-)
Mary