What is the difference between diffuse glass and diffuse coating

What is the difference between diffuse glass and diffuse coating?

Obtaining diffused light is possible using diffuse glass and diffuse coating. In recent years, diffused light has become the most widely used in gardening. This technology promotes faster growth of many plants due to better distribution and penetration of light rays, less light load on an individual plant, and also due to lower plant temperature. Diffuse lighting in a greenhouse can be created using diffuse glass or diffuse coating. What should you choose based on your crop growing conditions? In this article, our specialist will explain the difference between diffuse glass and diffuse coating.

What is diffuse light?

Diffuse light is scattered light that is evenly distributed in all directions without creating persistent shadows. This factor contributes to more complete development of plants. Diffuse light is extremely useful for growing tall, vertically growing crops with large leaves, as it allows for a significant improvement in the vertical distribution of light. Thus, the leaves located at the bottom of the plant receive more light than from direct sunlight. When the lower leaves receive more light, this accelerates the process of photosynthesis and the plant develops and grows much faster. For growing many crops, diffuse light is more useful than directional (direct) light.

What is the principle of operation of diffusion coating?

The principle of operation of diffuse coating and diffuse glass is the same. Both of these solutions help to diffuse light throughout the greenhouse with a low or high degree of diffusion. The differences between diffuse glass and diffuse coating are price, flexibility and durability.

Diffuse glass in agriculture

In recent years, the popularity of greenhouses equipped with diffuse glass has grown significantly, especially in vegetable growing. Many farmers who have built new greenhouses prefer diffuse glass. This glass is produced in two ways: by chemical etching or rolling.

Anti-reflective coating

It is important to always remember the fact that light diffusion is always achieved at the expense of a few percent decrease in light transmittance. For many crops this is not critical, however, for many vegetable crops (especially tomatoes) the presence of such a factor is extremely undesirable. In general, these crops can consume all the available light, and a decrease in the intensity and amount of illumination will lead to a drop in yield, especially if such a decrease in the intensity and amount of light is not compensated for in another way (for example, with CO2). To compensate for the decrease in light transmittance, the manufacturer can apply a special coating (one-sided or two-sided) to glass (diffuse or standard float glass), which reduces the degree of glass light reflection and increases the light transmittance of each side by several percent. However, the anti-reflective coating of glass is very fragile and may not be restored in case of improper use or maintenance, which will lead to the loss of additional percent of light transmittance. Fluorides have a negative effect on the properties of the anti-reflective coating, but other aggressive chemical cleaners can have the same effect. Little is known about this at this time, and the degree of harmfulness of liquids varies depending on the type of anti-reflective glass and the method used to apply it. A distinction is made between glass that has an anti-reflective coating applied using a sol-gel process and glass that has an anti-reflective coating applied by etching. Cleaning diffused glass with or without an anti-reflective coating can be more challenging than cleaning standard float glass.

Cost of diffuse glass

Greenhouse glass is not an investment for a few years, but usually for the entire life of the greenhouse. Diffuse glass (with or without anti-reflective coating) is more expensive than standard float glass. The cost of the diffuse coating is only a fraction of the price of new diffuse glass.

Flexibility

Diffuse glass provides diffused light all year round with the same degree of diffusion. Switching to other varieties or an entirely different crop is much more difficult than with standard float glass. The new variety or crop usually has different needs in terms of light and temperature.

In this case, additional protection may be required with a higher degree of light diffusion, or some of the light may need to be screened with chalking agents.

The increased light transmission provided by the anti-reflective coating on the glass may also cause additional problems for the new variety, for example if the fruit hangs high and close to the top, or if the crop is less tolerant to high levels of radiation.

On the other hand, a new variety or crop may require more light than the existing crop, and a reduction in the light intensity diffused by diffuse glass is undesirable. By using standard float glass in combination with chalk and reflective substances, growers can adjust the degree of reflectivity to suit the needs of the specific crop.

Density

A grower should always ask himself whether diffuse glass will be beneficial for the crop being grown. If protection is needed with chalk additives in the summer and spring, or with a mesh cover for most of the day in these periods, diffuse glass may only be useful in the autumn and winter. Note that there is too little sun in the Netherlands in the autumn and winter to require any further diffusion, and the natural sunlight at this time of year is inherently diffuse due to the cloud cover that occurs during most of the season. The decision should be based on the answer to the question: do the costs of diffuse glass outweigh the benefits?

Diffuse coating in agriculture

Diffuse coating also ensures uniform diffusion and distribution of light. Compared to glass, diffuse coatings are more flexible in use and are a good solution for existing greenhouses that are not equipped with diffuse glass. If you consider glass as a long-term investment, you can always choose the latest coating, which appears every year. The coating provides a slightly lower degree of light transmission (88%) compared to normal float glass (91%), however, it cannot cause any harm to most plants and has a very beneficial effect.

Diffuse coatings, like any chalk additives and screening substances, are easily removed using Removit. This operation can be carried out by the agricultural producer himself or by an outside organization.

Thus...

Developments in the field of diffuse coatings and diffuse glass are in constant competition in terms of efficiency. If greenhouses are equipped with standard float glass, the grower can take advantage of the latest developments in diffuse coatings that are introduced each year. Investing in new glass is usually a long-term investment, which in practice entails using outdated technology for many years if new developments have been made in the meantime.