DIY alkalinity standard

[taricha]

Very interesting, thanks for doing it!

I presume you know it, but others may not. The temperature of the kalkwasser is important, and it is critical to have no cloudiness or solids enter the test sample.

Yeah it's not a great choice of standard - temperature, solids, instability... Even diluted in the distilled water, it starts to form a hint of a crust on the top from reaction with CO2 within an hour.
Only really makes sense to use as a standard if you keep a bucket of limewater around anyway. Otherwise the other suggested DIY's are definitely less trouble.