John, here is XTOL quotes found in The Film Developing Cookbook, By Stephen G. Ancell and Bill Troop.(posted 8987 days ago)With the introduction of Kodak XTOL in 1996, still photographers became universally aware of ascorbics acid's potentialas a low toxicity developing agent. XTOL is the current state of the art in solvent developers XTOL 1:1 and more give a 60% speed increase without losing much latitude Kodaks XTOL can be seen as a radical update of the D-76 developer type. Recognizing the problems inherent in PQ developers with regard to environmental and image quality, Silvia Zawadzki and her co-workers replaced the hydroquinone with sodium isoascorbate (vitamin C derivative). Ascorbate has been characterized as a very sharp surface-acting developing agent. That, in combination with the low pH, results in negatives that achieve a better speed/grain/sharpness relationship than is possible with traditional developing agents. Fine grain and sharpness are also improved when compared to D-76 and T-Max developers. XTOL is now the developer most highly recommended by Kodak for T-Max films. It has been observed that dilution increases speed and sharpness with XTOL. Dilutions of 1:3 ....XTOL is effectively a nonsolvent developer, but because of its careful buffering, grain is still fine. ...ascorbic acid cannot be used as the sole developing agent unless fairly high contrast is desired. ...ascorbates are the safest developing agents both for humans and the environment yet discovered. There are many phenidone-based developers which increase speed by 60%, including XTOL, T-Max, FX 15, FX 37, FG7, Acufine and Microphen.