Perfecta-D is a highly concentrated, neutral tone Phenidone-Hydroquinone formula. Unlike other liquid concentrate developers, Perfecta-D Print Developer will obtain the maximum black of the paper. The standard dilution is 1:7, and the shelf life of the concentrate is at least 2 years Amazingly, this developer is both stable, long lasting, and a superior performer. Sequestering agents are added to developer to help them mix well - they isolate things in water, like magnesium, calcium, iron, etc. They usually impair the developers ability to produce a strong black, as will the addition of extra sulfite. Perfecta-D Print Developer contains sequestering agents as well as the additional sulfite, yet it will still obtain maximum black and yield a clean, full tonal scale. How? The chemist that developed it says "...the formula is better." Really? -- Why haven't Kodak and Ilford done this? "Because they don't have me" (the chemist). Modest, aren't you? "No," says the chemist, "modesty is like virginity - it's no fun." Perfecta-D developer can be diluted up to 1:14 and used with longer development times, or used in more concentrated dilutions. Fine Art photographers tend to try different dilutions and times with print developers and Perfecta-D will respond well. Perfecta-D is, amazingly again, quite good with old technology papers as well, like Elegance, although it does not provide the glycin "glow" of VersaPrint II, nor the flexible development options.