The Photographer's Formulary DK-25R Replenisher is used to extend the capacity of D-23 or D-25 film developer from 4 to 25 rolls per liter. As a developer is used, its action is weakened by the chemical reduction of the silver halides in the emulsion and by the release of bromide ions in the solution. The result of these activities make the film lose its effective film speed and lowers its contrast. The DK-25R replenishes D-23 or D-25 back to its normal activity and counteracts the effects of bromide build up. Shelf life of the replenisher is approximately 6 months.