When you boil this frilly-leafed green veggie, don't let the liquid leak out of the pot
[DOC] [TLE] Blanching Veggies with the Lid On or Off: Does It Make a Difference ... [PAR] Apr 8, 2009 ... Their explanation that acids trapped in the covered pot would turn the ... Well, it's 
a good thing we have Cook's Illustrated... ... "trapped" in both pots), but the 
vegetables all turned out bright green and tasty regardless of being covered.