This idea is for "all purpose" cleaning concentrates which are meant to be used very concentrated for heavy duty cleaning, and very dilute for light duty jobs.
For example, the strongest one is supposed to use Simple Green [link] is mixed with equal parts water for heavy duty cleaning (e.g., degreasing
engines), but it should be mixed 1 part simple green to 150 parts water for light duty cleaning (glass and mirrors).
If one mixes a particular concentration in a spray bottle, and doesn't use the entire bottle, you can't un-dilute it and pour it back into the original container for storage. And having several spray bottles, with several mixtures, takes up an excessive amount of space.
I propose a spray bottle which would have seperate compartments for water and concentrate, and a control knob to indicate what proportions should be used when spraying. This way, you can go from light duty to heavy duty cleaning with a twist of the knob.