Substrates: rockwool |

February 7

Substrates: rockwool

One of the most popular medium for soilless cultivation is without doubt the wool: made by dissolving at a temperature of 1600 degrees basalt, limestone and coke in a special furnace, is put on the market in various formats.

Although it is relatively new faces on the world of gardening, the rockwool exists in nature for centuries in areas with volcanic activity, where the magma is swept by strong winds creating long, thin fibers, however, must wait until 1865 for the man decides to produce the factory for use as insulation in buildings.

Will another hundred years before, in Denmark, you think of the use of mineral wool on a large scale commercial horticulture: from that time the publication was unstoppable, rising swiftly to Japan, where it is used for growing Rice, the U.S. and Canada.

Order to fully understand the qualities of this substrate is important to understand how it is produced: the molten rocks are put into a cylindrical container rotating and being added together with a resin based of phenol so that the potassium hydroxide and other elements do not separate.
At this point the amalgam being stretched and pressed in plates, with a particular attention to the force exerted, that will determine its density.

The sheets are lightweight and easy to handle, and are shaped in various forms, mainly "slabs" cubes for cuttings and germination of various sizes, graded and flaked for use as fertilizer.

The direction of the fibers is important: the vertical fibers are easier to reuse, are more draining, ideal for properly guide the young roots.
The length and the fiber density in the final product given by the speed of rotation during processing and by the force exerted from the press, from the composition of the rocks, and by the melting temperature.

Rock wool is a material made sterile by the high temperature necessary for its own manufacturing, and this has greatly facilitated its spread.

Of course, this versatile material is still widely used also in the building industry, but it comes to a product different from that conceived for the horticulture: the latter in fact has a different density, and reacts differently to water, also is absolutely inert and does not interact in any way with the nutrients.
It 's very important to use rockwool for gardening, even though the cost may be higher, and never fall back on what insulation for buildings, often produced with waste materials, saturated with metals (particularly copper and iron) and with a composition such as to inhibit the proper aeration of the roots and alter the pH value.

Although full of indisputable merits, rock wool also has some flaws.
If left exposed if he has been in a hurry to algae, and is sensitive to infestations of mushrooms: it is always good to cover the rockwool with a layer of expanded clay, or of black plastic, or in any case of opaque material suitable to protect the surface from light.
Moreover, handling the dry rockwool can be dangerous and you must wear a mask, gloves and clothing covering, to not risk contact with the mineral fibers.

Finally, the most sorrowful note: disposal.
Although it can be reused several times (after washing and disinfection between one cycle and the other one) it comes time to throw the rock wool, which, unfortunately, is a non-biodegradable material.
In Switzerland and Holland, where the consumption of this material in greenhouses is high, the law has been prepared for a controlled disposal, with collection and storage performed by the staff of specialized firms.
And 'the study reuse in terms of recycling in the cement, certainly more fruitful than simply transport the inert landfill.