The Chemistry of Clothes Washing #9: Hot or Cold #2

Following on from yesterday, there are several intrinsic advantages in  washing in hot water, such as increased detergent activity, increased enzyme activity, and the unlocking of the bleaching properties of the laundry bleaches (perborates and percarbonates) which are insoluble in cold water.

Are there any disadvantages of washing in hot water?

Potentially, there are a couple.  Firstly, some delicate fabrics may be damaged in hot water (so always check the washing instructions).  But this is less of a problem than it used to be and certainly less of a problem than most people think.

The reason for this is that most people at some stage have experienced damage to clothes apparently as the result of being washed in hot water.  This is partially true, in that hot water will certainly soften fabric structures and make them more prone to mechanical damage, such as could happen with older style top loader machines where the mixing action was quite aggressive and clothes would occasionally wrap around the central spindle.

But modern machines have a much more gentle action and this is nowhere near as much of a problem as it used to be.  And, of course, front loaders are even more gentle.

But are there any advantages to washing in cold water?

There are clearly no chemical advantages, but certainly several logistical advantages.  Firstly, it keeps energy costs down, although if you have solar hot water (as I have) this isn’t an issue.  Another advantage of course is that machines fill quicker with cold water than hot water which in some cases may be an issue.

One approach that was suggested on air is to dissolve in hot water the detergent and then tip it into a cold water wash.  This isn’t a bad idea, but the laundry bleaches may precipitate out, although you would certainly maximise their solubility in this way.

So if you are happy with the results in cold water using Cold Power or another brand so be it, but without a doubt the results will always be better in hot water with a premium detergent.

Tomorrow we’ll start looking at some common mistakes that people make when washing clothes, and then we’ll go on to look at stubborn stain removal and prewashes.

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