Speaking from the position of a guy that used a gas hotplate for his entire refining career-----you can break beakers, regardless of the type of heat you choose.
One of the problems I encountered on a regular basis was when refining polishing wastes. After thorough incineration and screening, they were subjected to a heavy boil in dilute HCl, to remove base metals and other substances that often make filtration difficult after the values have been dissolved.
Unlike Lou's scenario, bumping was rarely a problem in this operation, but solids accumulating on the bottom of the beaker, isolating the solution from the glass, was. The isolated area would get over-heated, then when the lot was stirred you'd experience an instant cracking of the beaker.
To solve the riddle, I got in the habit of stirring almost constantly, but that destroys the beakers in short order. The polishing wastes are generally filled with abrasives that erode the glass surface of the beaker as they're ground between the glass rod and beaker during stirring. Bad part was that the beakers were always large---3 or 4 liters.
I used gas because my hotplate pulled double duty, and, I must say, it served me very well. The left burner was set extremely high, so I could incinerate. The burner could still be used for evaporation and other processes, so I found myself running three burners almost constantly, unless I was incinerating.
Can't speak for the habits of others, but I routinely used a gauze pad, or an asbestos pad under my beakers. It provided the small amount of cushioning that helped prevent breaking beakers that were set down hard on the hard surface, plus minimized localized heating.
I'm not convinced I'd use the surface of any heating device without a pad unless it was one like Lou described, where the temperature was not excessive. You can't rely on that from gas or electric.
Harold
