Marking dark glass

I like to use strong colours in my work, such as black, dark blue, crimson and dark green to contrast with lighter colours or clear glass.

Way back on my NVQ course we were told to use permanent markers on glass, and I've never really thought much about it, coping with dark glass as best I could and then forgetting about the problems with it until faced with another piece of dark glass on the bench that has to be cut to shape. I've generally used a black 'Sharpie' pen to mark up glass, which are easily obtainable and leave a permanent line, but I've found it very difficult to see the line on some darker coloured glass.

I took an offcut of Wissmach Midnight Blue English Muffle into our local stationers - Howells of Biggleswade - earlier this week, and tried a couple of pens.

I found that ballpoint gel pens (available in gold, silver or white) work quite well - certainly clearly enough to see the line to cut, and the line left by the gold pen is narrower (perhaps 0.2mm) than that left by a slightly worn Sharpie (which could be upwards of 0.5mm). The gold line may not be quite so permanent as that left by a Sharpie but it's more than adequate for the temporary marking needed to cut a single piece.

The gold line stands out much better than the black on red water glass (the black line can just be seen, to the left of the gold one):

I think the gold gel pen cost £1.49 so didn't break the bank, and the shelf over my workbench now has one ready for when I need to mark some dark glass.