This is a follow-up to my earlier question about steaming using the Instant Pot. The answer there said that the "steam" function of the Instant Pot was only for pressure steaming; for ordinary steaming, one needed the optional lid that has a small hole for a steaming vent.
I have a lid that fits the Instant Pot exactly, but it lacks the steam release vent. How much does this matter? This question suggests that the venting holes in lids are generally too small to make much of a difference; but that was in the context of slow cooking, which generates far less steam. For steaming, would the absence of a vent cause too much steam to remain in the pot? Would this in turn affect the food being prepared?
As an experiment, I tried steaming idlis in the Instant Pot using the lid I have. I used store-bought batter that simply needed to be poured into the idli molds and then steamed for 7–8 minutes. I steamed the idlis for 8 minutes. During the steaming, the lid "danced" a little on the pot rim and steam was noticeably escaping. The idlis came out okay, but were a little sticky on the bottom. I'm wondering whether the lack of a vent hole on the lid could have caused this, or whether I should look elsewhere.
Best Answer
If a lid doesn't have a vent and the pot does not have any sort of locking mechanism like a pressure cooker, then the pressure of the steam inside will lift the lid off the pot and steam will escape. That was the "dancing" of the lid that you experienced. Venting holes in a lid just let some steam escape so the lid doesn't bang around, having a vent hole or not wouldn't make your idli's sticky.