Oscar asked: I've been playing with the technique of an early cartoon layer to start an oil painting, and, since drawing's my druthers, I've been trying out Sharpies and similar pens as a replacement for ink/thin black paint. Do you have any tips for this? Are markers likely to cause trouble in terms of paint reaction, color fastness, etc?
Oscar, Yes, beware of markers for underdrawing. You are safest with pencil, charcoal, or India ink. Once a long time ago, I used a black Sharpie marker for a preliminary drawing under an oil painting but I discontinued that idea because the dye had a nasty habit of bleeding through to upper layers. Covering the drawing with clear-coat layers doesn’t necessarily cure the problem of dye migration.
Markers are also prone to fading and color shifting. This is often a problem with drawings done entirely in markers. If you use different brands in the same drawing, they often shift in different ways. I did this marker drawing of a horse drawn milk wagon in 1981 but luckily it hasn’t faded too much because it was kept in the dark. Cool, dark storage slows down these processes, which happen at a molecular level.
Markers vary a lot in their dye and vehicle formulations — some are pretty stable— so the best thing to do is try out all kinds materials and procedures on scraps and put them in a hot, south window to test how they fare over time.