Rockwool pH Info

  • Thread starter jigglybones
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Stonewool is not alkaline!

It is a common belief that Grodan is alkaline and that one has to continuously adjust the pH. This is not true. When Grodan is new it contains some residual lime from production. Everybody should soaks the rockwool in no lower than pH 5 water the day before use. This is done to dissolve the lime. The lime will make the pH value raise a full point. Immediately before use; you flush the rockwool with your nutrient solution. When you flush, you also flush out the dissolved lime. From this point onwards rockwool does not change the pH in anyway.

Exception: If you condition your rockwool with a pH lower that 5, you may also damage the fiber itself. As an example: If you use pH 4 water for conditioning, the pH the day after will be 7. The lower pH you use the higher it jumps. Once the fibers are damaged it might take quite a while before the pH stabilizes. So never go below pH 5 with rockwool.



Thanks Jiggly, this is very interesting. I will be tring this within 2 days. I always have soaked them and the time I did go below 5, i believe it was a big jump. I never did flush them after soaking so it will be intersting to see., because I have 4x4x4 on a 4x4 tray on top od a a root mat. When the nutrient returns to the resi, I am pouring alot of ph down to bring it back to the number i want. Hope this is the end of this nonsense.
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