pH confusion

Discussion in 'Hydroponic Growing' started by growinINtheDrawer, Aug 9, 2017.

  1. Hello,
    So today I was getting my rock wool cubes ready to start another grow. I filled a tub of water up to soak the cubes in and started trying to get the pH down to around 6.0. My pH meter was just calibrated at the store and it said that my water started at about 8.02. I put 12 drops of my Mad Farmer "get down" solution and retested the water and it came out to be 7.63. Next I put in 25 drops and and retested and the pH and it was only at 7.40. I put another 30 drops in and my pH only went down to 7.27. Eventually I got irritated and just poured a splash of the "get down" in there and it came out too low so I added water to get it up to 6.0. Every time I tested the pH I let the meter sit in the water until the numbers stopped moving. I am so incredibly confused on why this happened. The first 12 drops brought it down by .4 and then 25 drops only brought it down by .2, without any water being added in between. If anyone has any idea of why this is happening I would really appreciate some insight.
    Thanks
     
  2. One reason is that the pH scale is a logarithm scale, and adding twice as much acid won't raise the pH twice as much. Another reason might be unpredictable reactions between the liquid and rockwool.
     
  3. I had never heard of a logarithm scale but that definitely makes sense. Thank you for your help!
     

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