The Chemistry of Clothes Washing #8: Hot or Cold

Should we wash our clothes in a hot water or cold water?

50 years ago this would have been considered a dumb question.  Washing clothes in cold water was virtually unheard of.  And there were some pretty good reasons for this.

Ultimately, the action of washing is all about chemical reactions, using the chemical properties of the detergents to remove certain chemicals (dirt and stains) from other chemicals (clothes).  And everyone knows that most reactions go faster at higher temperatures.  So it made perfect sense to wash in hot water.

But then along came Cold Power.  In what would have to be the most effective advertising campaign ever in Australia for a consumer product, Cold Power actually changed the way that people washed clothes.

Although some people were washing in cold water, usually out of necessity, the generally accepted view was that this was not be best way to do things.  But suddenly along came cold Power and made washing in cold water seem respectable

More than that, it actually claimed that it cleaned clothes.  That is, Cold Power made us believe that for the first time that washing in cold water was a serious option for someone who took the cleaning of clothes seriously.

So is Cold Power any good?  That is, do its claims stack up?

Well, Cold Power has certainly made a serious attempt at making a high – performance cold water washing detergent.  They did this by using shorter chain surfactants in their formula.  Although the shorter chain means that they are not quite as good at dissolving oils and greases (that is, they are less lipophilic) they are more water soluble than their longer chain counterparts, and this means that their activity is less a function of temperature, which means they work about as good in cold water as they do in hot water.

But how does Cold Power compare with the more premium powder detergents such as Omo, which has been the market leader for as long as I can remember?

Well, although I have never done a direct comparison, Cold Power simply cannot work as well as Omo.  That is, Cold Power in cold water cannot work as well as Omo in hot water.  It may well work just as well in cold water, but that’s not the point.

You see, OMO and other premium products contain active ingredients which are designed to work better in hot water than cold water.  Cold Power know this of course, and that’s why in their advertisements they always say that their product will outperform any other detergent in cold water.  But they never compare themselves with a premium brand hot water detergent.

You see, it is the laundry bleaches, the perborates and percarbonates, which really come into their own in hot water.  These chemicals are inactive in cold water, simply because they don’t dissolve – they need hot water to dissolve and do what they are put there for.  Anyone that has used a premium brand powder in cold water will at some stage have observed undissolved powder after the wash, and this is why.

So with the enzymes – they too work better in hot water.

More discussion on a hot versus cold tomorrow

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