Pen to mark molecular weight standards on radioactive blots ???

[Dr Engelbert Buxbaum]

josmarlangner at yahoo.de wrote:

> Hi there,
> could anyone please give a hint where to purchase pens to mark
> unlabelled molecular weight standards on radioactive blots? I don't
> think the ink is radioactive but it somehow gives a signal on the film
> (chemolumi?). I remember that I ordered such a pen about ten years ago
> but I don't remember where.

I got mine from BellArt Products, California (usual disclaimer applies).
The thing is non-radioactive, but contains a phosphorescent dye instead.
After exposure to ambient light it will glow for a while, long enough to
leave a "lasting impression" on X-ray film.