I've benn making several kalimba's in the last couple weeks. One of the side effects of tuning a new kalimba, or even playing the kalimba for a long period of time, is that the keys either give you a blister on your thumbs or it wears the skin thin. This is especially true when the ends of the keys are rough cut and not finished, as during the pretuning of a new kalimba.
So, I went back to a trick that I learned from Stevie Ray Vaughn. That's right I learned this trick directly from the blues master himself. You see in college I worked security for concerts. It was a great way to make some extra cash and get a great spot to hear the music. The evening that Stevie Ray Vaughn was in town, I was given the detail to guard his bus. I got to spend a few minutes with Stevie before the show while we were waiting for the super glue to dry on his fingers. That's right, Stevie played so hard every night on tour that it would literally rip his finger tips apart, so he applied super glue in layers to his finger tips. During the show, it would wear through the super glue rather than his skin.
I tried the same trip for my "kalimba thumbs" and it works great!!