Okay, so someone wants to be a smart ass on a Friday; that's cool, Milo. Just do you, man. I thought it obvious that the statement he made and I shared was in reference to heating with an oven or other dry source, but I suppose I should've made the distinction clearer. My bad. Thank you for taking the time to point that out.
Yea, I figured it was just an omission, but couldn't pass it up.
If thermal fatigue is actually an issue, then water should be more damaging than heated air as it has a much higher specific heat value and would transfer energy into the ball at a much faster rate than air.
A hot water bath would probably vary in temperature(thereby increasing the volatility) more than a dry heat source as well,
increasing the thermo-mechanical fatigue factor. Unless of course, the water bath had a constant heat source.
I suppose the argument could be made that water would transfer heat more evenly around the surface of the ball since it is in direct contact with the entire surface of the ball, but the air ovens all seem to have a fan that circulates the air around the ball.
Having said that, I have tried multiple methods. Hot water bath, covered bucket in the summer sun, trunk of a car on hot day, pro shop ball oven, dishwasher and currently use the Nu-Ball "Food dehydrator" ball oven. I've yet to have a ball crack from any of the aforementioned oil extraction methods. But I have had them crack in a controlled temperature environment just sitting on a shelf.