Make up a small amount of solution daily or every other day.
Make up enough solution to last for one week and store it in the refrigerator when not in use.
Make up enough solution to use for 1-2 weeks and add either natural or synthetic preservative drops to it in an amount specified in the literature. (Synthetic preservative mixtures, such as
, can be purchased from a chemistry or cosmetic ingredients source, and natural preservatives such as grapefruit seed extract can be found at most health food stores). I would personally still store this mixture in the refrigerator when not in use and discard after a couple of weeks.
It looks like you're new here. If you want to get involved, click one of these buttons!