While in Caffenol CS I adopted the philosophy of having a stock solution with both developing agents that will be activade in a 5% alkaline bath of soda, in Caffenol C21 I prepare first 1 liter of the 5% alkaline bath of soda and I add then 2 grams of coffee and 1 gram of Vit C and that's all. This developer can be used in stand development (agitation during at least 1 minute) and it doesn't need potassium bromide as anti-fogant or as restrainer. As restrainer it may extend the development time to not acceptable times. Even so, it takes 1 hour minimum, at 20 ºC to develop. I used it already with Ilford Pan F+ and gave fair results.