Grodan Improved Uni-Slab 9.5 x 8 x 4 in | Case of 16 Stone Wool

How a Grodan Uni-Slab Is Built and Why It Matters Two construction choices define this slab. The first is the wetting agent, which Grodan work through the fibre rather than spraying onto it. Water and feed then spread across the full width instead of running down a channel. Water content and conductivity read the same at both ends of a slab. Without that, a slab develops wet and dry regions and the plant on top of it gets an average of two different environments. The second is fibre orientation. The fibres run vertically rather than lying in a random mat, which moves water down and lets air in from the top. That produces a gradient with a drier upper layer and a wetter base, which is exactly the structure a grower steers against. Each slab measures 9.5 x 8 x 4 in and sixteen come in a case. The footprint takes a four inch block on top of it comfortably, which is how this size is normally run. Resaturation, Steering Range and Conditioning First Grodan describe this material as having a high resaturation capacity across a broad steering range. That phrase is worth unpacking, because it is the whole commercial argument. Steering means letting the substrate dry back between irrigations and controlling how far. A wide range means you can take it further down and still bring it back evenly. A substrate that will not re-wet cleanly channels instead. The next feed then runs past the root zone rather than through it, and the lever is gone. Condition the slabs before planting. Stone wool leaves the factory alkaline, and a soak in pH-adjusted water brings it into range. Skipping that step costs the first fortnight in iron lockout. Cut drainage slits after the slab has been conditioned and drained, not before. Key Features Case: Sixteen slabs to a case Slab size: Nine and a half by eight by four inches Range: The Improved range, with an advanced wetting agent in the fibre Even distribution: Water content and conductivity read the same across a slab Fibre orientation: Vertical rather than a random mat, which builds a gradient The gradient: A drier top and a wetter base, which is what steering works on Resaturation: High capacity, so a deep dry back still re-wets evenly Block fit: The footprint takes a four inch block on top Before planting: Condition in pH-adjusted water, as Grodan direct Drainage: Cut the slits after conditioning and draining, not before Technical Specifications Specification Value SKU 321147 Brand Grodan Product Improved Uni-Slab Material Stone wool Slab dimensions 9.5 x 8 x 4 in Case quantity 16 slabs Range Improved, with advanced wetting agent technology Fibre Inert hydrophilic fibre in a vertical orientation Resaturation High, across a broad steering range Conditioning Required before planting, in pH-adjusted water Alternative part numbers RW342680 and HGC713018