Gray white linen may be mineral deposits, not just dirt
The text in the pictures is in Thai, as originally posted.
💧 Gray whites are usually blamed on poor washing, but the real cause may be mineral deposits from the water
Is dirt the only reason white linen still looks gray and stiff after washing?
Not always. According to a 2021 study in the journal Polymers, calcium and magnesium in hard water bind with the soap in detergent to form insoluble salts that build up on the fibers as mineral deposits. Fabric with these deposits looks gray, smells, feels stiff and is more likely to irritate the skin. In laboratory tests, cotton washed 10 times in soft water (44.5 ppm) had ash levels close to unwashed fabric, while hard water (404.1 ppm) increased the mineral deposits.
What to do: test the hardness of the water coming into your shop before switching detergent brands, and compare it with the US Geological Survey (USGS) classification, which rates water above 180 mg/L as very hard. In hard-water areas, use detergent instead of soap. Because a US university guide states that whites can turn gray when too little detergent is used or rinsing is inadequate, check the water, the detergent dosage and the rinsing.
Think your linen fits this description? Ask the KHT team about your machines.