One way to get the water out is to steam it out: If you are 100% sure of all of the materials - including glue, paint, and lacquer - then you might try oven-drying it. Water turns to gas at 212/100 degrees F/C, so, if you have an oven big enough to do this, turn it on to a low setting of no more than 215 or the closest you can get to 212 without going below it. Bake it for 15 mins.
If you are unsure of the materials to make it - or you are, but you know the material won't survive 212/100 F/C, then you might try leaving it in the hot sun for several days. The caveat here is to take it inside when the sun goes down and bring it out at midday the next day.
If you are lucky enough to be near a beach, then you can bury it in sand - rather than leave it in the sun. The sand method is better because sand is made primarily of silicon dioxide, which absorbs moisture (hence the reason they put silicon dioxide tablets in vitamins, medicine, etc).
If you use any of these methods, then, you can insert the katana and repeat the process if the katana comes out rusty. You may have to repeat this for months, so don't give up.
WD40 works wonders, but, it is a water displacement (hence the "wd" in its name). But, it doesn't chemically change the water, nor does it get rid of the water - which still remains in the scabbard. Further, moisture - whether from water or from oil or from WD40 - could cause the scabbard material to swell, making it difficult to remove or insert the katana. If water enters the scabbard, the material might return to it's natural state once the water dries out (and it's entirely possible this won't happen either, depending on the wood or leather used to make it). And any oil will not dry out, so, permanent swelling is bound to result. WD40 will evaporate in time, so, in this regard, it would be like water.
A hair dryer will not work at all, unless you have an open end of the scabbard at the other end. Without air able to freely flow through (even if forced), incoming air will NOT enter the scabbard.
Dry it out with a blow dryer or something and clean it after use.
after its dry wd40 will help get rid of any moisture
...dry it out?
And now when I put my katana in, it comes out rusty later. I'm able to remove the rust but I'd really rather not have to do that, I might end up making a permanent blemish on my katana. Is there any way to fix this, or do I have to get a new saya?
