10 Jan
2006
10 Jan
'06
4:09 a.m.
----- Original Message -----
From: Pete Turnbull <pete at dunnington.plus.com>
Date: Monday, January 9, 2006 10:22 am
Subject: Re: cleaning keyboards in the dishwasher
Some of you seem to have slightly odd ideas about detergents :-)
I know of no dishwasher detergent that contains chlorine (which is a
gas) nor large amounts of chlorine-based bleaches. (Mild)
Bleaches and
brightners are common in *clothes* detergents where there are good for
stain removal, but they're *not* good in dishwashers, where the bleach
would tend to fade patterns on crockery. Therefore dishwasher
detergent manufacturers use only very small amounts, if any, and
they're usually oxygen-based.
More to the point though, they don't contain silicon dioxide, at least
not any I've come across (btw it's silicon, not silicone). They might
feel gritty, but that's not sand, it's solid detergent. Ok To start with
I'm no expert. Having said that I feel free to
pontificate!
Dish washer detergents have changed considerably over the past fifteen
years in response to concerns about the eutrification of waterways as a
results of detergent contamination. This has resulted in a very
dramatic drop in the phosphate content.
A dishwasher detergent has to shape up or "polish" the incoming water
supply and combine with and remove the grease etc present. To this end
they may contain silicon dioxide in the form of cage compounds which
capture metals etc out of the incoming water and prevent a metallic
stain building up on dishes as the water is dried on them repeatedly
over a period of time. To detect the presence of these try and repeat
your experiment of dissolving dishwasher detergent completely, its a
lot harder now than it used to be. As you so rightly state chlorine
based bleaches are rare in dishwasher detergent, however high
temperature based Oxygen bleaches are becoming more common to break up
grease etc. To test for these add close to boiling water to dishwasher
detergent and you will normally find that a large amount of gas is
released.
Finally the very dramatic corrosion that can occur with aluminium
appears to be electrolytic in nature and is generally strongly promoted
when the aluminium is in contact with another metal such as stainless
steel cutlery. This is the basis of one method used to polish silver,
where you line a vessel with tinfoil (aluminium) and place the
silverware in there with plenty of hot water and a little detergent or
preferably washing soda.
My 2c.
All the best
Laurence Cuffe
> Because
of the above 2 items you might want to use "hand"
dishwashing
detergent, but not much since it will foam,
I would suggest crystal soda, it is a good detergent and not overly
caustic, and the rinsing cycle will get rid of residues.
Ammonia solution would work, but would be quite smelly. Finally, detergent won't damage copper, aluminium,
steel, or other
metal. Water will. Detergents can remove oils and other thin-film
coating that might protect metal, so it is wise to dry things
carefullyafter getting them wet because water and air can cause
corrosion, but
it's not the detergent that does that, it's the water. Well, actually
it's the air, but water permits various electrolytic reactions that
hasten the process.
--
Pete Peter Turnbull
Network Manager
University of York