“Blias” in today's pots and pans

Question

Throughout all of Yoreh Deah Chelek Alef and Hilchos Pesach (and perhaps other places in Shulchan Aruch as well) we see the idea of "blias" ("absorptions") by celim. That is to say there is a "taste" that is left in a pot or pan after cooking in it. Therefore if someone would cook meat in a pot, then within the same day cook milk in it (even though there is no meat in the pot now), still there is a "taste" of meat that was left inside of the pot walls when it was first cooked. That taste will now come out of the pot when cooking milk in it and will prohibit the milk.

This is all true of a metal pot. However, a glass pot, according to the Machaber, doesn't take in any taste at all. On the other side of things, if one has a pot made of "cheres" (earthenware), he would never be able to expunge taste from it once it was cooked in (not like a metal pot which one could kasher by making ha'galeh on it).

I'm having a difficult time understanding how this din (rule) is still relevant to today's pots. Is there really a taste left inside of a metal pot? Once upon a time a metal pot that was cooked in over time would slowly become dirty, grimy, filthy, covered in black, clearly used. One could look at this and understand that there is a "taste" left in the walls of the pot. However, I don't see how this is true of a normal metal pot in today's market, which is smooth, finished off, and more or less retains it's original color and look and stays clean over time. Where is the "taste" in the walls of this pot? If someone would cook milk or meat in it and then cook water in it, would the water have any taste to it (assuming the pot was cleaned in between)? While I don't see any posek (halachic decisor) using this argument even as a "tziruf" (argument in combination with other leniencies) to be lenient in a question of issur v'heter (forbidden combinations), still, I'm looking for any poskim that perhaps spoke about this or entertained the possibility. Maybe today's "metal" pots are more like a glass pot, which the poskim say doesn't retain any taste of what's cooked in it.

Answer 1

From a Kosher Spirit interview with Rabbi Chaim Cohn:

KS: Can you share a unique experience that you had while working at the OK?

RCC: I once had an argument with a plant engineer concerning whether or not stainless steel can absorb or not. He maintained and brought extensive documentation to prove that stainless steel can’t absorb anything and therefore should not need kosherization. I told him, your proofs are impressive but the Rabbis decreed 2000 years ago that metal needs kosherization and I do not have the authority to go against them. We agreed to differ.

Approximately a year later, I was in the process of supervising the kosherization of a 1000 gallon reactor and after the workers had meticulously cleaned it we brought it to a boil. There was about a quarter of an inch of scum on the top of the pot. The engineer was passing by and I called him over to look at it. I said, “This was a completely clean pot.” I turned to the workers and asked, “Right?” The workers nodded their heads vigorously up and down. The engineer looked at it and said, “ I can’t argue with empirical evidence,” and walked away.

Six months later I got a call from the engineer. He said, “Rabbi Cohn, I now understand.” “Great,” I thought, and asked, “You now understand what?” He answered, “I understand why a stainless steel vessel will absorb.” I asked, “Why?” He answered, “You have to understand, when it leaves the factory it can’t absorb anything, however, when it is heated it expands and contracts and it will produce micro fissures. Your Rabbis were right, you can’t measure this and therefore have to assume the worst-case scenario that the entire volume has absorptions in it.”