I'm having trouble getting even skies using pyrocat-hd at 1:100, 3 liters per 11x14 tray, and foma film in 8x10, and am curious whether this is a problem of technique or materials. I should say that I'm tray processing and developing by inspection, and that my dev temperature at present is around 74-75 deg. Not every neg w skies shows unevenness, and negs without skies show none, at least that shows up on a print. The kind of unevenness is of 2 types. Either along the edge of the sky, when there's a small amount of sky at the top, and it looks like a sine wave (loosely speaking) alternating areas of lighter and darker sky. The other type is where in a large expanse of sky, there'll be blotches or spots in the middle.
So, would cooler developer make a difference, or is it a matter of especially finicky materials when it comes to sky tones? Any and all pointers are appreciated.