Reforming
From The Glossary of Digital Photography
The process of resetting the capacitors on an electronic flash so they can be fully charged. If a flash is not used for a long period of time, recycling during operation can take a long time and the resulting flash output is lowered. Reforming the capacitors can help. Reforming is done by inserting freshly charged batteries, letting the flash charge, firing it off at full power, letting the flash charge again, and firing the flash at full power again. Continue this process for a number of cycles. It is often necessary to let it cool down for a few minutes every five to ten flashes.
