The Chemistry of Clothes Washing: Enzymes revisited


Over the years the concept of the laundry prewash has changed.  Essentially, they used to be degreasers.

The idea was that a solvent would solublise an oil based stain (including things like inks) and allow them to be washed out in the water.  The trick with these was the washout part, as if it wasn’t done right, there could be a residual solvent smell, and this was occasionally the problem with Preen trigger.

Certainly, if you were to use an automotive prewash (that is, use an automotive degreaser as a laundry prewash) this is what you’d probably get if it was solvent-based – you can get the residual smell of the solvent.

So the early Preens and SARD products were sophisticated degreaser formulations.  This gradually changed, I think initially in an attempt to make the product cheaper by switching to water-based formulas, but perhaps also because the understanding of the requirements of the prewash had changed.

What sort of things do we use a prewash for anyway?  Is it mostly oils and greases, or is it things like mud, or food or wine stains?  If it is the former then a solvent-based product is the way to go, but if it is the latter, which seems to be the case, then enzyme-based products are the way to go.

But even as this changed in the marketplace, advances in enzyme technologies meant that they could now to a great degree work just as well on oil based stains as the earlier solvent-based formulas.

Enzymes are remarkable chemicals in that they are highly specific in terms of what they react with.  They are exceedingly large and complex molecules and all have names ending in “ase.”  For example glucose oxidation is an enzyme that oxidises glucose.  Proteinase is a molecule that reacts with proteins, and so on.

And so now more upmarket laundry formulations, as well as prewashes contain a cocktail of these things – each targeting a particular type of stain.

Protease targets proteins and is by far the most widely used class of enzyme.  It aids in the removal of food stains with a protein base such as eggs and meat, and also blood and grass.

Amylase enzymes work on food stains containing starch, such as rice, spaghetti sauce, potatoes, oats and gravy.

Lipases target oily and greasy stains such as collar grime, butter and oil, and some cosmetics such as lipstick.

Cellulase enzymes remove pilling and fuzz from cotton fabrics and have a whitening effect.

In fact, it could be argued that the enzymes are what separates the men from the boys in terms of washing formulations.

We will summarise things tomorrow, and look at some common mistakes that people make.

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