Thanx, I've found stamps and just about anything red do not like each
otherG, be it cancels or envelopes. I read somewhere one should use
cold water for that and to place the stamp face down to minimize the
water soaking into the colored envelope.

John Mycroft wrote:

I use very hot water on early Germany and early Canada with excellent
results but watch out for stamps that are printed with water-soluble ink
(not all catalogs tell you that which is a shame). Also, don't use very hot
water if you are soaking off coloured paper or you are likely to wind up
with a bowl of pink / yellow / whatever stamps. Particularly bad are stamps
stuck to the type of airmail envelope with red and blue stripes round the
outside.