Kirk, I can show you some pictures of my handwriting. But my handwriting sucks. These were drafting pens that I used to use 42 years ago in high school. And I sold my whole set away. Found out later they were useful for what I do now. I don't think you'll have a problem writing on glass. I would least go the next size bigger , or two sizes bigger. And stick with their ink or the one of the white that I posted earlier. No problems with smearing after it's dry under a clear coat. JF p