Coagulation is the result of cell desiccation, where the cells are not allowed to be heated to the point of "explosion". The cells are instead heated to a point where the fluid content of the cell evaporates through the outer cell membrane resulting in cell collapse.

Fulguration is a type of coagulation in which only the surface cells are desiccated so forming a layer of eschar which seals the operation area. It does this by using sparks, similar to those used in the cutting techniques, but with the difference that the sparks do not "explode" the cell but "squeeze" the water out.

The important feature of the coagulation wave-form is that unlike the cut wave-form which is continuous, the coagulation wave-form is switched on and off. This applies the power for only a limited time (approximately 2:25) with the effect that the water is not heated instantaneously, but slowly enough to allow dehydration, without cell wall destruction.

Fulguration should be contrasted with desiccation as each type of coagulation is vital to various kinds of surgery i.e. fulguration for urology and cardio-thoracic surgery and desiccation for neurosurgery. Fulguration always produces necrosis where ever the spark lands, due to the very high amount of energy in each spark. Desiccation on the other hand does not have this concentration of power, as the power load is limited by the area of contact between the electrode and the tissue. As a result, desiccation may or may not produce necrosis depending on the current density at the contact point.

The term "crest factor" has been used by one American company to quantify the on/off characteristics of this type of coagulation wave-form In technical terms this is defined as the ratio of peak voltage to RMS voltage and in a good generator will be constant over the total control range.

Fulguration	Desiccation