What is a Wetting Agent?

Wetting agents are a class of surfactants used to break surface tension and allow substrates to absorb water more easily. Wetting agents are especially important under dry conditions where the substrate  can develop hydrophobic properties – with tendency to repel water; unable to be easily wetted.

The main reason for using a wetting agent is to allow the substrate to be re-wet easily if it becomes dried out. This may be due to long delivery times and different cultivation practices. The wetting rate is very important, as it is the absorption rate that ensures a more even water uptake.


Hydrophobicity is caused by various hydrophobic organic materials, such as organic acids, resins, wax. When they are dry, they form a non-polar coating on the substrate particles. Non-polar substances are not easily wettable in water, which is a polar substance. Then the coating repels water and the substrate in a dry state is unable to wet and to rewet.


How do Wetting Agents work?

Producing substrates, we add a wetting agent to ensure that the substrate will have good wettability. Wetting agents reduce the hydrophobic behavior of the substrate by decreasing the surface tension of the water. Due to its hydrophilic properties, it attracts water while adhering to a hydrophobic non-polar surface.

The purpose of using a wetting agent in substrates is to support re-wetting, especially during the first weeks of cultivation – its performance must be focused on this period. Once the root system in the pots has formed, re-wetting the substrate is easier, even if the wetting agent is no longer active.

The wetting agent does not affect the total water uptake of the substrate. Wetting agent ensures that the substrate does not hold more water than it would without the wetting agent.


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