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Ask Dr. Laundry

Ask Dr. Laundry

Crystallization of Bleach on Floors

By Dr. Laundry February 22, 2012

Q:  I’ve seen on a few posts that mention bleach can crystallize if proper conditions are met. I work at a company that uses Clorox to sanitize the floor and some of the equipment. I find that after cleaning, when the equipment is moved or the floor remains wet, a layer of “crystals” is found. Trying to clean it using a mop and room temp water causes the crystals to spread into a thin layer, which is eventually removed.  However, if I add more Clorox, it crystallizes further. I read in some of the other blogs that hard scrubbing and warm water is the best removal process, but I’m more interested in prevention. What are the causes of crystallized bleach? Could a constant source of airflow (air filter system for example) cause the liquid in Clorox to evaporate quicker than expected forming the crystals?

A:  The crystals you are observing are salt crystals.  That’s because the sodium hypochlorite active in Clorox® Regular-Bleach breaks down into salt and water (a big part of what makes it so environmentally friendly).  Also, note that undiluted bleach is mostly water – as the water evaporates, eventually salt crystals will remain. 

There are several possibilities as to why you are seeing salt crystals on the floor.  The most likely reason is that the floor is not being rinsed thoroughly following cleaning or the bleach solution being used is too concentrated, making complete rinsing difficult.  The correct protocol for disinfecting floors, walls, vinyl and tiles is:


  • Pre-wash surface, then mop or wipe with a solution of 3/4 cup of bleach per 1 gallon of water. Allow solution to contact surface for at least 5 minutes. Rinse well and air dry.


If your job involves sanitizing food contact surfaces in a restaurant, you would use a different bleach solution and method than what we recommend for floors.  For all you “foodies”, here’s the protocol:

  • To sanitize food contact surfaces: wash, rinse and wipe surface area with a solution of 1 tablespoon of bleach per 1 gallon of water for at least 2 minutes. Let air dry.


Has anyone else had problems with bleach crystalizing?