I guess I'm slow today. Are you asking when you'd need to wash an old sock so that it could be used again for polishing? If so, I would say never! Why would you want to get polish on other garments? Just throw it away when you think it is no longer doing the job.Do socks have to be 100% cotton to polish shoes? Or can any old socks do the trick? After how many polishes would you need to wash the sock to re polish?
Everyone wants to know these answers but im the one to ask.