Leaching and clouded glass
A cloudy glass is not dirty. The haze is the surface of the glass itself, and every additional scrub makes it worse.
In detail
Glass is not chemically inert over long exposure to water. Alkali ions migrate out of the surface layer and are replaced by hydrogen from the water, leaving a depleted, microscopically rough layer that scatters light — the effect is called leaching, and in the trade it is glass sickness or dishwasher etch. Federal conservation guidance states the cleaning consequence plainly: scrubbing the surface of clouded glass will not change the appearance, because the clouding is not a deposit but the result of chemical leaching action, and repeated scrubbing can damage the surface. That single sentence resolves one of the most common frustrations in domestic cleaning. A glass that came out of the dishwasher cloudy and stayed cloudy after soaking, after descaling and after polishing is not a cleaning failure and no product will fix it. The distinction to make first is limescale versus leaching: limescale is a deposit sitting on the glass and a mild acid removes it, while leaching has removed material from the glass and nothing puts it back. If an acid soak makes no difference, the answer is that there was nothing on the surface to remove.
Why
- Glass is explained by Leaching and clouded glass
Sources for this page
Sources
Conserve O Gram 8/1: Removing Dust From Ceramic And Glass Objects
National Park Service, US Department of the Interior, 1993 · Government or regulator
Relied on for: That scrubbing the surface of clouded glass will not change the appearance because the clouding is not a deposit but the result of chemical leaching action, and that repeated scrubbing can damage the surface. (states this directly)
Verification: a person has read the passage relied on.
Read on — 'Avoid Wet Cleaning', 'Why Dust?', 'Objects Not to be Routinely Dusted', 'Preparation' and 'Procedures for Removing Dust' in full. Supports the claim as stated. Clears dry dust removal and a specified damp-wipe solution on glass and high-fired ceramic within stated conditions, and supplies the mechanism for why a cloudy glass never comes clean.
Last reviewed by a person on .