If
one gives wool to the dyer, and it got burned in the cauldron, the dyer
pays the value of the wool – because he is a paid custodian,
responsible for accidents.
If he dyed it poorly, the dyer gets
the lesser of the improvement to the wool and his expenses. Since he
knew that using inferior dye would result in inferior product, he is a
damager. His claim to compensation is that he did in fact increase the
value.
If he was to dye red, and he dyed black, Rabbi Meir says
that he pays the value of wool, but Rabbi Yehudah awards the claim as
above.
Test yourself