Water, KOH (Kalium hydroxide).
Both antimicrobial and cleansing.

Use a pot (No aluminium, preferable stainless steel) with 50/50 ashes from hardwood and preferably rainwater (no chloric ingredients  which one can find in most of tap waters ). use a mesh to get only the finest ash and not the coal or other things. Cock this “soup” either on a high temperature for a short while like half an hour, or if you are using a woodstove which you probably have, hence the ashes!! – and leave it on lower temperatures something between 5-10 hours or over night. Remove what’s floating on the top. Let the ashes sink to the bottom and you will see a clear brownish ash water on top of the ashes. I use a deep scoop and remove the juice and filter it through a coffee filter though its not always necessary. Then cook it again to concentrate it, usually you need to boil it down to the half of what you had, if you had one litre you boil it down to 1/2, or boil it so long until you see crystals forming in the bottom =)
You are done. You have now a concentrated potash water, with usually a pH of 10-11. This can be used for cleaning everything you can imagine, I use it for toilet cleaning, as a shower spray, for my bathtub, I clean the woodstove widow with it, just experiment with it!! Its fantastic for your bathroom if you have tiles where they become darker especially around the shower: you spray the tiles, leave it an hour or so, and its very easy to brush it away! If it hasn’t ben done a while use on top of the potash water Limonelle Acid spray, leave it 1/2 hour and brush away =) 
I use 1/2 teaspon Xanthangum (or any other thickening agent) to make it thicker for use as toilet cleaner. 

Quite alkalic, so don’t get it in your eyes, and wash your hands after use.

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