Humidity can cause a lot of issues in your sublimation printing. It can affect both printer and paper. If it’s too dry, your printer has a hard time keeping its heads free and clear as the ink could dry and clog up nozzles. It only takes some cleanings to get them back but is still an unneeded headache.
With too much humidity, your paper acts as a sponge. You’ll notice when you arrive in the morning that the edges of your paper are curled up. This can be a big problem if you start to print. Your head can catch on the curl and damage itself, causing an expensive repair.
If you do notice a curl, cut the paper yourself before engaging your printer.
Too much humidity can also cause major gassing once pressed, possibly causing out gassing in your image and ruining it.
-Kevin Lumberg, Johnson Plastics Plus