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Blog | From dew making machines to moisture measuring devices | EP&C

From dew making machines to moisture measuring devicesSomething big often starts with something quite small. Take August Gronert, a clever inventor who applied for a patent on a dew making machine in a greenhouse back in 1935. For Gronert this invention was the start of a very successful company which subsequently went on to apply for a further 56 patents. In this edition of ‘old patents from the world of horticulture’ I will take you through how it all started for Gronert with the dew making machine. At the end of the blog, you will find a competition about the purpose of this machine. So be sure to read through to the end. 

The dew making machine explained

For some plants to thrive dew needs to form, just as it does in nature. This dew then has to collect on the underside of the leaves. To achieve this, Gronert came up with the following setup: a cultivation box (a) filled with soil (b) containing plants (c) with a heating pipe (d) hanging alongside it. The heating pipe (d) is embedded in a water-absorbing casing (e). Any moisture contained in the casing (e) will evaporate when the heating pipe (d) heats up. Above the box (a) there is a guiding surface (f) the purpose of which is to direct the accumulated water vapour past the plants (c). To stop the water vapour from condensing against the guiding surface (f), the guiding surface (f) is made from a material that does not conduct heat very well. On top of that, cold air is circulated along the top of the guiding surface (f). This also cools the underside of the guiding surface (f). This will cause the temperature in the crop room to drop. And voilà, you have dew. 

The beginning of something bigger

Gronert's expertise in the field of moisture then extended to other fields, such as the drying of harvested potatoes and grain. He was most successful in developing gravimetric moisture analysers. These essentially consist of a set of scales with a collapsible heater above them, so that samples can be weighed before and after drying without the need for a separate oven. For this, he founded the company Ultra X and applied for patents in the most important countries in the world. He would have been proud of the fact that his granddaughter currently heads the Engineering department.


Now back to the dew making machine. When I delved into the old patent, it was still unclear to me which plants Gronert actually needed a dew making machine for. The only example mentioned in the patent is mushrooms. Which other plants do better with dew as opposed to dripping or misting? I even asked ChatGPT, but that didn't really get me anywhere. I wonder if anyone knows which other greenhouse crops dew might be important enough for to start using Gronert's invention commercially in a greenhouse? I want to invite you to speculate and let me know what you think. You could end up winning a good bottle of wine by e-mailing your substantiated entry to