Pesachim 16 - What did Rabbi Akiva add?

Rabbi Akiva added to Rabbi Chanina’s testimony  by stating, "Kohanim had no problem burning oil that was only slightly ritually impure in a lamp that was more ritually impure." How is that an addition to what Rabbi Chanina had said? Both state that one can add to the already existing impurity when the food is anyway being destroyed? And actually, what new did Rabbi Chanina say in the first place? A food can not make other food impure anyway!?

In order to answer this, the Talmud has to introduce two new concepts. True, by Torah law one food cannot convey impurity to another. However, the Sages, out of love for the purity of holy foods, added a law that food can (as if were, by this new decree) convey impurity to another food. We thus see what Rabbi Chanina is teaching us.

Rabbi Akiva seems to be adding nothing: if you count the degrees of impurity in his example, they are the same as in Rabbi Chanina’s. We are forced to say that the lamp that Rabbi Akiva is talking of is made of metal. Metal has the law of impurity different from other materials: it acquires the same level of impurity as the person who touches is, not the usual one-degree lower. Thus, Rabbi Akiva is teaching us that the oil was acquiring two degrees of impurity in the process, and that this nevertheless was permitted.

Art: The Metalworker by Rudolph Ernst