....They had a fountain of water coming out of the center, my guess a 4-6-inch main water line....
Could you make heads or tails if this system was running during the quench, did it appear to create significant aggitation to the water?
Many tutorials recommend aeration for varying lengths of time, but then to shut it off prior to quenching. Then temperature of the water would likely be uniform, but I wonder if only so much air can dissolve in the water. It's curious to me that the water temperature that you settled on may be able to carry more dissolved air in it than at warmer temps.
The reason I think it might matter is because I suspect there might be vapor jackets that form and collapse around the hot parts, but not necessarily steam? The O2 that forms the oxides that eventually show as colors must come from somewhere, but too much doesn't seem to help. A prequench aeration likely has other benefits, too.
Just rambling around. I can't easily get to my little hobby setup right now, but it does make me want to play with it some more. Take care.
