Basically, you are doing the same process involved in transparency processing - you are creating a silver image that is subsequently bleached away, and the remaining silver is a negative of the positive image that was removed. This remaining silver is then developed in room light to create another negative image that duplicates the original negative. There is a good article on unblnkingeye :
http://unblinkingeye.com/Articles/NbyR/nbyr.html
that explains the process in detail. Also click the link the Liam Lawless article and read that article. The only thing i would recommend is doubling the concentration of the sulphuric acid in the bleach if you are using common auto battery acid to make it. And wear gloves and safety glasses whenever you mess with this sort of stuff!