I manage a neuroscience centre. We have a host of neuroimaging facilities including MRI and EEG. Electroencephalography (EEG) is a technique that measures the electrocortical activity of the brain. (Bear with me knitters, I have a knitterly point to make here.)
When doing an EEG recording, electrodes which detect the electrical activity generated by the brain are arrayed across the scalp. The electrodes are embedded onto a cap, sort of like a swimming cap, which comes in many different sizes to reflect head sizes. (For the geeks out there, these are 64 channel EasyCaps, supplied by Brain Products GmbH.)
EEG caps are extremely expensive pieces of high tech equipment. They are fragile and must be treated with care. The conductive gel which is used to guarantee a good connection between the electrodes and the scalp is sticky and grainy. After using the caps, they must be very carefully washed, dried and stored. The caps are gently scrubbed using a soft toothbrush and baby shampoo. They are then left to dry. In the lab, we have a series of glass heads, in different head sizes, which are used for drying and storing the caps. The washed cap is stretched over the appropriate size glass head and left to air dry.
I was intrigued when finishing my Peerie Flooers hat by the suggestions knitters made for the best way to block a hat. Some people found a vaguely head sized bowl to dry the hat on; some (rather ingenious) people blew up balloons to the right size and dried the hat on the balloon; many people, I suspect, put the wet hat upon their heads and let it air dry. I, however, have a laboratory full of glass drying heads in every imaginable head size…….