Chipped Volcano Bowl Repair

I thought I remembered a thread about repairing chips in a volcano bowl, but I can't find it now.

My wife found me a volcano bowl for $3 at the local Sal Army. The bowl is relatively craze-free, but it has several 1/4" x 1/2" chips out of the glaze on the side of the volcano. Does anyone have suggestions for coloring & protecting these areas? I'd love to be able to use it as a volcano bowl, but at the very least I'd like to protect the chipped areas from dirt & moisture.