Did another test print. "Hello world" exposed with a transparency film onto the case of a hot glue gun.

The exposure time was 18 minutes. Slightly longer than usual, i am still experimenting with the timing. However such a long time was not necessary, the text came out slightly overexposed - the letters are a bit thicker than in the exposure mask, because the longer you expose, the more the edges of the artwork expand. Staying around the 10 minute mark seems to be optimal. The artwork expansion could also be accounted for in the design stage.