How do I choose a shading agent?

The use of a shading agent is a simple and flexible way of protecting your crops against excessive heat or UV radiation. The agents can be easily applied, and the shading duration and effect can be varied. We supply a range of products from which you can select the appropriate shading agent, depending on the desired shading duration.


Chalk (calcium carbonate) is a commonly used shading agent. By applying this shading agent on your greenhouse (referred to as chalking) on time, you can influence the climate in your greenhouse.

Heat reflection and shade

Chalk reflects the sun, thereby reducing the temperature in the greenhouse. The shading effect of the chalk on the greenhouse roof also reduces the amount of sun rays entering the greenhouse. Particularly in the summer, the use of shading agents help to create the best cultivation conditions.

Powdered agents

Our environmentally friendly powders La Blanche, Witvast and Spuitkrijt consist of calcium carbonate, mixed with a number of other components including a glue component for adhesion. After mixing with water, it can then be applied to the glass, foil or polycarbonate.

La Blanche is a tried and tested product that is sold worldwide from the Netherlands to Australia,

Ronald de Vreede, Account Manager Houweling Group

Liquid agents

Our liquid shading agent La Blanche Liquide can be applied in various doses. Compared with our powdered agents, it lets more light in during rainy days. On cloudy days a higher light intensity can be realised by spraying the greenhouse roof using roof sprayers. La Blanche Liquide can also be used on, for example, skylights.

Shading duration

The shading duration and cover can be varied by diluting the La Blanche or Witvast. In the following overview you can see the consequences of dilution.

La Blanche Shading duration* Cover
1 zak / 100 litres water 4 months 80-85%
1 zak / 150 litres water 3 months 60-65%
1 zak / 200 litres water 2 months 50-55%
Witvast Shading duration* Cover
1 zak / 100 litres water 2 months 70-80%
1 zak / 150 litres water 1,5 month 50-60%
1 zak / 200 litres water 1 month 40-50%

* The shading duration is an indication; the eventual shading duration depends on the weather conditions.


The advantages of using our shading agents are:

  • improves the greenhouse climate
  • suitable for on glass, foil and polycarbonate
  • simple to use
  • made from natural raw materials
  • can be applied by hand and machine
  • slowly wears away
  • no cleaner necessary
  • good value for money


Our powdered agents La Blanche, Witvast and Spuitkrijt are packaged in bags of 25 kg. Liquid shading agent La Blanche Liquide is available in buckets of 20 kg.

We care. We do. We fulfill.

Read the instructions on the label before use. Feel free to contact us for personal advice.