Anyone know where the CRC gets this from?
“The other issue is that due to the weight and thickness of cast iron cookware, the metal will not get hot if one m erely dips into the hag’alah water for a few seconds. Rather, the items should be put into the boiling water and left there for l ong enough tha t the water itself comes back to a boil, which indicates that the cast iron itself has become heated to hag’alah temperatures.”
You can kasher stone and wood which are much poorer conductors of heat than cast iron, and these things take a long time to conduct heat. (Just think- If you put a decent sized potato in boiling water it will take close to 30 minutes for the center of the potato to reach 200F). One would have to leave the stone or thick wood utensils in the boiling water for ages to get the center of the material to hagalah temperatures. Presumably as long as the water maintains its bubbling and it is al ha’aish it has the ability to draw out beliyos regardless of the utensils internal temperature. The same should hold true for cast iron. I get the need to bring the water back to boiling part since that is necessary for the hagalah to work, but that should have nothing to do with the cast iron utensils temperature. It’s been a while since I’ve gone through the sugya. Is there something I’m missing?
I'd assume, just based on your excerpt:
If they were worried about the internal temperature of the pot, their guidance is pretty weak, as you point out.
more likely, potato/wood etc., being bad conductors, don't much cool the water even while remaining internally 'cool', hence the boiling will resume relatively quickly. Heavy cast iron, being a better conductor, will actually perceptibly cool the water, requiring a short wait until the water returns to boiling. Once the water is back to boiling, we no longer 'care' about the internal temp
seems in psak they agree with you in any case, perhaps just poorly written explanation of the issue