i agree that nomex is hydroscopic in its bare form jowever when it is used with a standar resin system it wick the varnish very nicley to give the material a very high resistance to moisture intrusion. Sealling it ou if you will. Most of todays transfromers are also varnished using a vacuum impregnation insulation system which further gaurds against intrusion of moisture etc because it drives the varnish deep into all the little tiny crevasses in the lamination stacks and the winding itself. Anyhow a good cleaning and a bake out to dry these items along with a redip and bake can bring a lot of these units back to very good condition in my opinion. of course any questionable megger reading after the unit cools from the oven then dont hesistate to scrap it..