This particular filament (Sunlu matte HS PETG) is one of the absolute worst I've ever used WRT being hygroscopic. It arrived so wet that I had literal steam from the extruder the first time I wanted to use it. It took almost 48h in my drier to dry it completely so I could use it. Its been sitting in an airtight box with dessicant for 5 weeks and I needed to dry it for >16h for it to be usable again. The wet part in this print was in the bowden tube between dryer and printer, I restarted the print after took this image.
Sure it prints well at 300mm/s, but it is by no means matte at the temperatures that allow printing it at high speeds, it is actually very glossy. A huge bummer.
smooth first layer...so nice
This is the only PETG I've ever had this issue with, normally I can just store them with dessicant and it's fine.
Right now RH is fairly low around 30-40% because it's cold and winter, summer its usually around 60-80% here.