[Marc Smith]

Preparing Kalkwasser

The more hobbyists you listen to, the more methods you will come across about how to prepare Kalkwasser (Limewater) in the proper manner. This is unfortunate, as it is confusing for beginners especially. There really is no one and only propper manner in which to prepare Kalkwasser ideally.
All methods advocated are really not that much different from one another. Some hobbyists may use a little more calcium hydroxide and others may use a little less. The concensus, though, is that the chemical to use is calcium hydroxide (and not calcium oxide).
Do not expect to find the ideal way here either. All I am going to give you is the method that I have used for years. I have always been satisfied with the end result, and have consistently obtained KW with a pH of over 12.2, and a pH that maintained itself.

How is this done?

Using treated water, that has gone through a reverse osmosis filtration unit and then through a silicate removing compound, I add 3 level teaspoons of calcium hydroxide, per gallon of water, that I prepare.
I then very gently stir the mixture. Not forcefully, just gently, to mix to powder with the water evenly. The reason I mix it gently is to prevent (or minimize) the amount of carbon dioxide that gets into it. After I finish mixing, powder settles to the bottom of the vat. That is normal since not all powder will dissolve. Water can only absorb so much calcium hydroxide before it becomes saturated. This is a chemical fact. Note, also, that cold water absorbs more of calcium hydroxide than lukewarm water or warm water.
What should the pH be

After I have mixed the powder and the water, when I place a pH electrode in the mixture I will get a reading of over 12. This has been so each time I prepare the KW in that manner. This is encouraging as fully saturated KW has a pH of around 12.4 or thereabouts.
In any event, regardless of what you do, you must ensure that as little carbon dioxide as possible gets into the water and calcium hydroxide mixture as this would result in the formation of calcium carbonate that will settle to the bottom, and does not dissolve. This process also lowers the pH of the mixture, which is not desirable.
This is an easy method to follow.
Every time you prepare more Kalkwasser I recommend that you dispose of the excess powder in the bottom of the container. This is not a must but it is better, in my opinion, to do so.







~Marc