Since I'm out of town I figured we'll cover some basics that I was going to explain later, but now's as good a time as any. Someone recently commented that they want the things that are bad for your marker to be bolder so they are easier to avoid. Here's a list of things I would try to avoid coloring over:
1. White Out- No way should you color over white-out. Besides looking bad on paper it leaves a white spot on the marker tip. the photo shows how coloring over white out shows up worse than ever, and it can leave gunk on your marker tip.
2. Unfired Clay- this will discolor the tip because bits of clay are clogging the fibers. Also avoid plaster. Clay coated papers also should be tested, some will work and some won't.
What is OK: Ceramic paint-it-yourself ornaments are great. Sculpey, after it's baked looks real neat. Glazed Ceramics are Ok too, though those are pretty slick surfaces.
3. Acrylic paints- You can get away with some quick work but if you try to color over most acrylics they will clog your marker tips/discolor your tips.
4. Chalks/Oil Pastels- Nope. Do these after you color with marker, not before.
5. Untested stamping inks- These will stain you tips and it may come back off when you least expect it. See the post on Testing stamping inks for more info on how to throughly test an ink.
6. Solvents or oils: These are just a bad idea to color over. They are fine to use over the top of your marker drawing though, and won't hurt it unless they contain Alcohol, Ethanol, or some other similar chemical.
Rule of thumb- If it is something that when it gets wet it smears and is opaque, STAY AWAY or test it first.
Things that won't hurt your marker, just make the tip look UGLY:
1. Pencil- I once had a colorless blender that I didn't change the tip on for almost 4 years. The tip was grey and people thought I was coloring with a light gray marker. The tip was fine, and the blender ink was clear, but it had become gray from all my years of going over pencil lines. If you go over a thick pencil line quickly scribble onto some scratch paper to get it off your tip. Same with Colored Pencils. They won't hurt your marker, just make the tips ugly (see photo)
2. Watercolors- These are so thin that you usually won't have a problem, but they might discolor the tip. If you want to use watercolors, use them AFTER you use markers.
Rule of thumb: In Japan Copic markers are commonly used with watercolors, pastels, colored pencil, acrylics. However, they use them AFTER the marker work has been done. Also, any other inks that are not allowed to dry enough that usually work with Copics will discolor the tips. Your pale colors will show damage the most.
It's easy to switch out a tip if you have ruined it beyond help. Get a pair of tweezers (Copic tweezers have little gripping teeth that make removal easier) and pull the tip straight out. Then, insert the new tip by pushing it straight in where the old tip was. Let the marker sit for a few minutes so the ink flows evenly.
This is not a complete list, but I am hoping that if any of you have run into other marker no-no's you can share these with us.