hist-brewing: Re: sanitation/detergent vs. soap

Jeff Renner nerenner at umich.edu
Mon Jul 31 06:16:51 PDT 2000

Al Korzonas <brewinfo at xnet.com (BrewInfo)> writes:

>Detergent doesn't ruin head retention... soap does.  Big difference.
>Sodium Carbonate (washing soda) is a great detergent and doesn't leave
>the soapy film that you are thinking of.  Soap suds... detergents don't.
>The problem is that many cleaners are mislabeled as "detergent" when
>they really are "soap."

I'm not sure I agree with Al on several things here.  First, soap and
synthetic detergents are both surfactants, or surface active agents.  This
means that they reduce surface tension, or make water "wetter,"  which
helps clean things by making the dirt rinse out or off things more easily.
Their molecules also have an oil attracting end and a polar, water
attracting end.  This means that they will make oil and water mix, which is
handy for cleaning as much dirt is oily.  I don't think sodium carbonate
would really be a detergent, although it may help cleaning.

Mild warning - some sorta technical stuff follows, but I think I've made it
pretty straight forward and I hope understandable, and it's stuff that is
useful to know as a consumer, I think.

Soap is an organic salt made from a fatty acid and sodium (or potassium)
hydroxide.  This salt is very soluble in water, which is a good thing for
soap to be, of course.  However, in hard water, calcium ions (Ca++) will
displace the sodium ions (Na+) from the soap molecule.  It's an energy
thing, you don't need to know why it happens, it just does.

Unfortunately, while sodium soap is very soluble in water, calcium soap is
very insoluble.  We have a name for it soap curd - or bathtub ring.  Since
it isn't soluble, it can't participate in cleaning.  This is where water
softeners come in - they substitute sodium ions for the calcium ions in
hard water.  Water with no calcium (or magnesium, which acts like calcium)
is called soft because of the way it behaves with soap - no soap scum.
Adding washing soda will have a similar effect by putting in a whole lot of
sodium ions, which keep more of the soap soluble.

Soap scum is bad since it won't rinse out and traps dirt (bathtub ring).
You can scour your bathtub but your clothes will not rinse clean and your
hair will be dull and stiff.  Incidently, it is the lack of soap curd that
makes people feel they can't rinse soap off when they shower with soft
water.  Actually, they are rinsing off far more than with hard water, it's
just that it remains soluble and slippery.  In hard water, it is not
slippery, even though there is lots more left on your skin.

Synthetic detergents were developed (I think in the 1930's) to work in hard
water - they remain soluble in hard water, so they will clean clothes,
hands, dishes, hair, etc. in all kinds of water, although you need to use
more in hard water.

I don't think there are mislabeled detergents that are actually soaps, at
least as far as major manufacturers products go.  There are very few actual
soaps left on the market except for bar soaps - most are detergents, and
even some bars are synthetics (Zest and Dove are two - do you remember the
TV ads for Zest showing how there was no scummy deposit on eyeglasses that
were dipped into sudsy water with Zest as there was with soapy water?).
Virtually all major manufacturers' laundry products are synthetics - Ivory
Flakes may still be soap; I think Duz is gone.  Dishwashing liquids and
dishwasher powders and liquids are all synthetic, as far as I know.
Household cleaner are likewise except for Murphy's Oil Soap and perhaps
some others, but Mr. Clean, Spic n' Span, etc are synthetics.  Shampoos are
too - you wouldn't like the results with hard water and soap.  That's why
women used to use rain water for shampooing - or beer!

I make my own soap and really like it with my softened water, but I'm
certainly glad for detergents.

For beer glases, I use hand dishwashing detergent and just rinse really
well.  Seems to work pretty well, but not great.  I know brewers who use
nothing but hot water, but that won't remove lipstick, and it just leaves
me uncomfortable anyway.


Jeff Renner in Ann Arbor, Michigan USA, c/o nerenner at umich.edu
"One never knows, do one?"  Fats Waller, American Musician, 1904-1943. 

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