I've been given a number of old B&W photos to scan and restore. Many date from the 30's to the 60's although some may be older still.
A number of them have been drawn on in biro(ballpoint pen).
Can anyone suggest a method for removing the biro ink that won't damage the print?
If restoration of the original prior to scanning is the aim, that's a tough one. There are a couple of complications that make this more difficult with photographs than it would be with ordinary documents or paintings in common media (watercolour, oils or acrylics).
There are essentially two ways to remove the ink: using a weak solvent in combination with local suction (think a vacuum cleaner the size of an airbrush nozzle) or non-abrasive absorption (usually some variation on the Q-Tip theme made from skewers or toothpicks and cotton wool, rolled or dabbed rather than swiped); and selective laser evaporation. The second is probably beyond your means as an individual, although you may be able to hook up with a university lab or a major art/document conservation shop.
The first complication is that the ink is not nearly as easy to remove after it has cured (oxidized); ink that is relatively fresh responds well to solvents (you merely need to dissolve the binder), but fully-cured inks will have polymerized and need to have the chemical bonds weakened and broken. That means more solvent action, which brings us to complication number two: there is a strong likelihood that some, even most, of the prints were done on resin-coated papers. If everything below the ink is water-soluble or hydrophilic (the emulsion, the paper sizing, etc.), then selectively dissolving the ink is tedious, but relatively easy work, even if the solvent penetrates the emulsion. If the paper is resin-coated, you need to be very, very careful to lift only the ink and avoid delaminating the paper and emulsion while the coating is soft.
The work is delicate and would require testing, and would probably amount to tens of hours per print. Unless the original prints are of historical significance (say they were printed by Ansel Adams or Edward Weston or somebody of that stature), I would leave them in their current condition and attack the restoration problem only at the reproduction stage. Scanning in full colour will help considerably to identify and remove not only the ink, but other environmental damage. Scanning with different settings (assuming your scanner/software supports it) can help to isolate known damage, automating its removal somewhat (though you'd still need to fill in the blanks).
I would seriously suggest reading Ctein's Digital Restoration from Start to Finish for a thorough overview of the subject. There are very few real shortcuts, I'm afraid, but there are a lot of things that can make the job easier than it might otherwise be.
