I just made a test with a no name metallic gel roller pen. It blocks the light completely. It is a 2 USD pen that was bought for my 3 year old daughter at the postoffice. I think Your should be able to that kind of pens everywhere. It takes some time for it to dry. Another possibility is to ask at an artsupply, they might have a pen that is better suited.
I talked to a local artist supply and they sell a "lead" grease pen, that can be used on glass and other smooth surfaces. They said it will block light. You can remove with any de greasing agent (whatever that is). I have ordered one and will test if it works.
You could also do this on the computer, if you wanted to have your sig in back, and a nice border around it.
Just sign a black peice of paper a few times, scan in the one you like with a cheap flatbed, adjust your size in MS paint or whatever, and add a border. Then print it off in a transparency like a teacher uses for overhead projectors, (any university/community college library copy machine prints transparencies), usually about 50 cents each.
If you want a black signature on a white background, you can print the transparencies in silhouette.
I've use transparencies, for particular effects when helping my little girl make photograms.
More than a decade ago I had an embossing die made and I have used that on all Cibachrome prints. I also emboss B&W proofs and finals like this, specifying a deep white or black border (for fibre paper or Cibachrome, respectively). Why? Because I could never agree as to how I should sign my name, so an emboss settled the argument for all time — for me at least!! :rolleyes:
I never sign anything on mats, framed or unframed. Just the hidden emboss for perpetuity and let the image speak for itself.
“The photographer must determine how he wants the finished print to look before he exposes the negative.
Before releasing the shutter, he must seek 'the flame of recognition,' a sense that the picture would reveal
the greater mystery of things...more clearly than the eyes see." ~Edward Weston, 1922.