I have a little problem with decals. I set decals to my hasegawa B-17 and afterward bottoms of the decals turn out white. whats the reason for that? i´ve had that problem only with Hasegawas decals.

If it's just the bottom of the decals turning white then I would suggest it's the excess water carrying the adhesive down and then evaporating leaving the adhesive behind. Try blotting more of this excess water away whilst placing the decal, and pressing the decal down with some clean tissue.

Vinnie