The chochmas adam in 48:16 rules that if one cooks a davar charif in an eino ben yomo meaty pot the davar charif becomes meaty but the pot remains eino ben yomo due to not bar not. In Chapter 49 the Chochmas adam rules in a case by a meaty knife cutting a davar charif and then a parve knife (or meducha) afterwards cuts the same davar charif. In that case he rules that the parve knife becomes meaty and anything else cut with that knife that is charif would also become meaty. My question is once we say not bar not from the now meaty onion into the parve knife isn’t the knife really considered parve and now the next davar charif cut should be also parve. It seems strange to me that the same knife on a certain level is parve and even if one cut hot cheese with it the food would be kosher be’dieved but at the same time the knife would cause a davar charif to become meaty if it cut the charif. Do we really say the not bar not taste from the meaty onion into the knife would be reawakened by a davar charif and make the next charif meaty?
The principle of the Chayei Adam (48), which is based on the Shach (122:2; 97:7), is that the ‘enhanced’ taste within a davar charif (which was received from taam that was original pagum) is kalush, a weak taste, and it does not impart taam meshubach to other items. Therefore, the taste in the pot remains pagum, and only the taste within the davar charif itself is ‘reawakened’ to become meshubach.
Therefore, we have a situation whereby the pot is meaty but only on a level of taam kalush, or nat bar nat (as Chochmas Adam writes at the end of 48:16).
In 49:10, Chochmas Adam states that the a parev knife cutting an onion that became meaty by being cut with a meaty knife, itself becomes meaty. The implication is that it becomes totally meaty, not only on a nat bar nat level. However, this does not contradict 48:16, because it would seem that the meaty knife that originally cut the onion was a ben yomo knife, and therefore the taste in the onion does not require the special effect of davar charif to make be mashbiach it, but was rather meshubach to start with. This type of take is strong enough to be inparted back to another knife when cut (and would also be strong enough to be imparted to a pot, and so on), and the knife is therefore meaty for all intents and purposes.
Sorry for the delay in replying.