One tenth is a strange amount, isn't it? Like, who has a 1/10th teaspoon measure lying around?? What I did: I used my smallest measure, which was 1/4 of a teaspoon, and I filled it up a little less than full (guessing it was about 1/5th of a teaspoon, and then I halved that. After a time or two you can just eyeball it; you'll sort of know the amount just by looking at it.