I have never heard about this seasonal change of the sizing.
Originally Posted by Vaughn
Arches platine is, however, for all I know not marketed primarily as a water colour paper, but, as the name indicates, for *alternativeprocesses*, foremost, of course, platinum prints. Now pt/pd is a rather easy process, but I have hade difficulties with some batches making pt/pd prints also. I once or twice got my money refunded, but not the hassle. Good batches generally work normally with pt/pd or kallitypes, though. New cyanotypes are more fickle, and here Arches Platine drove me crazy by once working and once not, until I discovered the citric acid precoating method. Chrysotypes also are less easily made on this paper than one might think; as often as not I ended up with some undesirable pattern of patches which only became visible when the paper was dry.
This Bergger paper is apparently a baryta paper without baryta coating, but cut to photographic sizes. This alone makes it uninteresting for me. I want to print on watercolour for the haptics and the subtle paper tones (I certainly don't need this pure, brilliant white), and tear the paper to sizes I want.