[quote="Jorge"]If you are printing with borders, lith tape will hold the paper and negative together and give you a white border.
I have observed that when printing pure Platinum, rubylith tape does not block all the uvies and a smudgy gray border is produced. I like my images to float in the middle of the paper, so I have taped the negative to the paper with rubylith and then taped over that with Mylar silver tape, taking care to keep the very sticky Mylar away from negative or paper. My experience with masking tape is that it is generous with its adhesive and gives it up to the negative and the paper. This is more apparent during a one-hour stint in the printing box with a PMK developed negative. After an hour the printing frame (and any tape) gets warm.