*Update: I ran these mugs through the dishwasher and they held up! The blue almost faded away completely but the black and the red are going strong! Hooray!
>> Draw on your design with regular old Sharpie. The oil paint marker will definitely last longer. That's just the way it goes. But since I usually hand wash my dishes, I didn't worry about it. You can print off a design and transfer it by rubbing pencil on the back of the picture and tracing it onto the mug (like this). You can also (sort of) draw with pencil on the mug first.
>> If you make any mistakes, dip a cotton swab in some rubbing alcohol and it comes right off!
Mug Baking Tips:
- In order to make the mug (at least hand) washable, the glaze on the mug needs to melt a little and incorporate the Sharpie ink so it sort of becomes part of the glaze. Then when you wash it, the ink doesn't just smear off. That's why you should use a cheap (but oven-safe) mug. The glaze will be lower quality and therefore more likely to heat up the way you want it to.
- Bake at 450° F instead of 350°F. Place your mug upside down on a baking sheet in the oven, then turn the oven on. Once it's preheated, set a timer to 30 minutes. After the 30 minutes, turn the oven off and leave the mugs inside to cool with the oven. This will prevent cracking and/or exploding mugs. (They probably won't explode but I'm not a mug science expert.)
- If you use colored Sharpies on your mug, the color will fade. That's one way to tell if your mug has baked long enough: the color should be noticeably lighter. I only used a blue and red color. The red turned to a orangey-red, but the blue stayed pretty much the same although slightly lighter. So, I wouldn't really recommend using any color lighter than red. Of course you could, but it's more likely to fade away completely and more likely to come off when washing.