by gently heating NH4NO3

Duralium, the alloy from which it is made tends to get brittle when it is hammerred.
You have to temper it back by gently heating and cooling with oil.

If your honey crystallizes, you can easily re-liquify it by gently heating the jar in a pan of hot water, stirring while heating. Do not overheat as heat may alter flavor and color as a result of carmelization of the sugars source: http://homecooking.about.com/od/foodstorage/a/honeystorage.htm

Heating Copper Sulfate gently drives off the water of crystallization leaving an amorphous white powder. This is purely a physical reaction. Heating this powder strongly will cause a chemical reaction liberating sulfur dioxide and oxygen, leaving black copper(II)oxide:

2CuSO4 >2CuO + 2SO2 + O2

more gently, most gently