Expert: Henry Boyter - 2/4/2005

Question
As a preschool teacher I need to know if the bleach in my center is still killing germs? It is kept in its origional container untill it is mixed fresh each day. I wanted to use some, straight from origional container,  to remove marker from a table and it did not. It has a mild bleach smell and yellowish, clear color. Also tested it on fabric, straight from bottle, it did not bleach out color. My question is, If bleach dose not remove the color from fabric (or irratate skin) is it still killing germs? I asked the Clorox bleach Co. got no response. Asked center for disease controll, no response. I think we should play it safe and get new bleach. My director wants prof. I hope you can help. Thanks, K. Wieske  

Answer
Bleach can last for months if not years, depending on storage conditions, but to know its exact strength requires a test.  The test is about $30-50, for which you can buy many new bottles of bleach.  As for the marker, I would not expect bleach to remove it.  Those take a different solvent system.  With fabric, it depends on the fabrics and dye used.  If you want to see if there is any chlorine left, put a couple of drops of iodine in water and then add the chlorine.  The iodine color should change/disappear.

Again, since a bottle of bleach is around $1 on sale, just buy a new one yourself.  Lastly, even straight bleach does not kill all germs when you clean.  Some germs are just resistent and you just aren't a perfect cleaner.  Also, overuse of germ killers can backfire.  Remember when you kill the bad germs, you also kill the good ones, some of which help keep the bad germs in check.  Again, all this depends on conditions, etc.  This is more of an interest when you stop cleaning.

As far as you director goes, he must know that "proof" is not possible without considerable testing.  Just sounds cheap, but if you are cleaning daily, a bottle of concentrated bleach should run out long before it loses its strength if keep in a closed bottle.  Try the iodine test and see what you get.


Henry Boyter, Jr.
PhD Chemist

The opinions expressed are those of Dr. Boyter and
are provided for informational purposes only and
should not be used as advice.  No warranty or
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