salt precipitation (for protein/collagen) - (Sep/09/2007 )

how does exactely the procedure of collagen (or any protein) salt precipitation go?
any protocols?
i just know that i can precipitate the collagen in my sample using 4M NaCl. i just added it and centrifuge i have got some pellet but still in doubt ..cuz in some places they say about slowley adding and waiting for some time and stirring...

so please i appreciate your experience and knowldge sharing..

thanks

Try Googling "protein precipitation salt" and see what comes up.