Whats this about rockwool having a high pH that requires leaching before use?
Rockwool essentially has a neutral pH. All bonded horticultural rockwool (ie., slabs, blocks, plugs) are held together with resins that are employed in the curing process. These resins are > 8.0 pH BUT they do NOT affect the pH of the growing medium (they can be extracted by boiling in water). One manufacturerleaves residual lime in the material (a benign artifact of the production process) and so they require an extended soaking period prior to use. This is not required with General Hydroponics rockwool products.
