Callosity, like all biological processes,works at different rates for different people. I myself within a week had developed decent enough calluses to play for a while, andwithin a month I had full thick hard calluses. Right now I've no feeling in my fingertips, which is the only draw back. It's just like tan; some people get a whopper tan within two days, while for others it takes two
weeks.
I've got callus on my strumming thumb now![img]smileys/smiley4.gif[/img]I can smack acoustic steel strings as hard as I want with no pain whatsoever! That took me ages to develop; I think you actually
have to give yourself blisters for that to develop.
You can get callus on any part of your skin; for example Thai Boxers have callus on their knuckles, shins, elbows and knees.
All medical practitioners will tell you thatcallus is a bad thing, because:
A) It leaves you wide open to infection
B) Your skin is effectively left numb
It's interesting to read up on it:
http://en.wikipedia.org/wiki/Callus
Here's a random little excerpt:
Deal portering is heavy and dangerous work which cannot safely be undertaken by any save experienced men. The shoulder of an experienced deal porter is said to develop a callosity which enables it to bear the weight and friction of a load of planks. But even with a hardened shoulder the deal porter has an unenviable task. To carry over a shaking slippery plankway a bundle of shaking slippery planks, when a fall would almost certainly mean serious injury, is work for specialists."