I am going to attempt to use ferri bleach on some of my images to bleach back the image and then continue development in lith developer. I will be using PF ferri powder and wanted to know how much to use to make a solution. How much powder per litre of water to mix? Also, how long does it last? Is it something that can be reused, or is it really just a one shot deal? I have an accurate scale I can use to weigh the powder.