Wayne Boatwright wrote in
. 190.14:

Ever notice how quickly the signature space on the back of your
credit/debit card smears or fades beyond recognition, and how difficult
it is to re-sign it? It usually happens because of moisture on the
fingertips or natural skin oils.

A few months ago when I receivd a replacement card, I masked off
everything but the are where the signature is signed. After signing it
with a ball point pen, I sprayed two light coats of Krylon Matte Finish
(suitable for plastic) over the siguature. The signature still looks
like the day I signed it.

Other brands of similar sprays will certainly work, but it should be a
matte finish (you can't tell it's there).

HTH


Clear duct tape. Done.