Rockwool Slab

Last updated: November 22, 2021

What Does Rockwool Slab Mean?

Rockwool slabs are a form of rockwool, a natural growing medium made of spun basalt and chalk to create a dense fibrous material. To form rockwool slabs, the materials are spun and melted, first forming a cotton candy-like material that is them formed into block-shaped slabs.

Rockwool slabs are primarily used for hydroponic drip irrigation systems during the second and third phases of plant growth.

Rockwool slabs come in various lengths and widths (narrow vs. wide) and come poly-wrapped to protect the medium from degradation.


Maximum Yield Explains Rockwool Slab

Historically, rockwool was used as an insulation in homes and other structures. However, gardeners in Denmark started to use rockwool to start seeds, cuttings, and seedlings, and the success continued from there.

Rockwool slabs retain water and nutrients well compared to other growing mediums. The slab’s fibrous consistency also traps air to provide valuable aeration to a plant’s root system. Large rockwool slabs can easily secure the roots of adult plants in place and provide valuable, much-needed support.

The chalk used in the manufacture of rockwool has a high pH level, which must be brought down prior to planting within the material. Most growers soak the rockwool slabs in pH-adjusted water to adjust the pH to levels of 5.5 to 6.5.

Once the pH has been adjusted, the rockwool can be used for planting. Most rockwool slabs feature holes where a seed, seedling, clone, or rockwool cube can easily be placed.

Rockwool slabs are also known as stonewool slabs. In addition to rockwool slabs, there are also rockwool cubes available on the market in multiple sizes. Rockwool slabs are lightweight and can be reused, making them a popular choice in commercial operations. Unlike cubes, rockwool slabs are less portable.



Stonewool Slab

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