The Chemistry of Clothes Washing #11: Prewashes

The story of laundry prewashes is a fascinating story in itself.

The first one on the market in Australia was Preen aerosol.  It made a huge and immediate impact on the market for two reasons – firstly, the concept of spraying something onto a stain before washing it had never been heard of before, and secondly because it worked so well.

It’s extraordinarily good performance resulted from its use of trichloroethane as its solvent, which used to be drycleaning fluid.  Thus, you essentially hand the ability to spot dryclean your clothes.

The solvent-based formula was very good at getting out the kind of things that ordinary detergents wouldn’t, such as oils, greases, ink, lipsticks, shoe polish and so on.  It wasn’t so good at inorganic stains such as clay and mud.

It was followed soon after its introduction by Charge, a Johnson & Johnson product.  Charge was a water based formula which was utterly useless, and wasn’t even worthy to tie up the bootstraps of Preen.  Because it was water-based, the only type of stain for which it would outperform Preen was clay and mud, but these weren’t that hard to remove any way.

Some time later, SARD decided to get in on the act, with SARD Wonder Spray.  Unlike Charge, the SARD product was a serious competitor to Preen.  The reason for this is that it was also solvent-based, with an extraordinary 45% surfactant level (as opposed to about 12% for Preen).

The reason for such a high surfactant level was probably because they couldn’t figure out the right blend to enable it to do all the things that is required of a prewash – dissolve in the solvent, allow the solvent to dissolve a stain, allow it to be emulsified in the wash, and finally be washed out.  The Preen formula did this very effectively with only 12% surfactant, but the SARD product no doubt required 45% because they simply had not worked out quite how to do it as efficiently.

Anyhow, it worked.  I was out of the industry by the time it came onto the market, so I have never seen a direct performance comparison, but it’s highly likely that it worked just as well as Preen.

Unfortunately, for consumer products, performance is nowhere near as important as perception of performance.  And good as the SARD was, it was never going to displace Preen as the market leader, and with what was no doubt an expensive formula, the people at SARD at some stage pulled the pin and withdrew it from the market.

This left Preen all on its own effectively.  And what happens when a product has a monopoly, is that they tend to make it cheaper to allow the company to make more profits, and hope people don’t notice it.

The first change was to the Preen trigger formula which had come onto the market in 1985.  It too was solvent-based, but with a more parafinnic type of solvent (like kero).  This meant it was even better on oil based stains than the aerosol, but not quite as good with inks and shoe polishes.

In the early 90s be solvent changed to isopropanol, whose only claim to fame is that it is almost entirely odourless.  It certainly was not as effective a solvent as the original solvent.

At some stage both the trigger and the aerosol became water-based which of the course made them a lot cheaper to make.  The reason they could get away with this is that this coincided with advances in enzyme technology that allowed them to be entirely enzyme-based products.  This has its pros and cons, which I won’t go into now.

Tomorrow I think I might revisit enzymes and go into them in more detail.  As they are now an integral part of both detergents and prewashes, it’s good to understand what they are and how they work.  Then after that, unless I get distracted by something else, I’ll tie it all together and discuss some mistakes that people make when washing clothes and a few other tips.

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