How Do You Clean Weathering Sponges?

[Kombi]

I've only recently attempted to use the Tamiya weathering master kits and it's pretty neat what can be done. However, there's one thing that I'm a bit baffled on. Can you clean the sponges off and if so how?

I've noticed that they don't exactly wipe off clean, but I'm not willing to try water or solvent just yet. I can accept that I should buy one per color, but I figured I would ask.

Thanks!

[Kombi]

I appreciate the reply, and it seems like an easy enough solution. I'll have to pick up a few more now. Pity about them being in the cosmetic section though.

[935k3]

The weathering kits are based on the acrylic paints. I clean mine with ammonia. Also the can easily be removed with windex or ammonia. Alcohol would work but it's probably harder on the applicator.