Ilford Microphen is a fine grain developer recommended for obtaining the maximum film speed with films that can be push processed. It is optimized for use at the faster end of the exposure range. Grain size is reduced and grain clumping is prevented because of the low alkalinity of the developer.
The majority of developers which give an increase in film speed usually produce a corresponding increase in grain size. Microphen, however, has been specially formulated to overcome this disadvantage, and therefore has a high speed to grain ratio. That is, there is a speed increase while giving the type of grain associated with a standard developer. A speed increase can be achieved with many films and meter settings up to EI 3200/36 can be used with Ilford HP5 Plus film.
Microphen is supplied as a powder and shows exceptional consistency in performance throughout its working life. It is made up to a stock solution for normal tank and tray use, and can be further diluted 1+1 or 1+3 for users who prefer to use fresh solution each time.
Ilford Microphen Film Developer datasheet.