Early on, softened water made by technologies like zeolite softening or chilly lime softening was a precursor to modern-day UPW remedy. From there, the time period "deionized" water was another development as synthetic IX resins have been invented in 1935 and afterwards grew to become commercialized while in the 1940s. https://newsprospect.com/the-ultimate-guide-to-pure-water-cleaning-with-a-water-fed-pole-for-solar-panel-cleaning/