A Handy Prewash

Prewashes aren’t what they used to be. The old Preen aerosol was based on 1,1,1-trichloroethane, the solvent used in dry cleaning. So when it came to getting stains out of clothing, there wasn’t much it wouldn’t shift.

But those days are long gone. These days they are all water-based, with the main cleaning agents being enzymes and oxidisers. These are both high-performance additives which, depending on the concentrations involved, do a good job of removing food stains, vegetable and animal oils and fats, dirt, urine and other biological matter.

But they’re not so good with industrial stains – engine oil and so on.

For this, you want some Kenco:


Image result for kenco degreaser

And it’s even packaged in a spray bottle for you. Keep it in the laundry, and it’ll do a bang-up job of getting industrial oils and greases out


Laundry Prewashes #5

The final approach to laundry prewashes is that of the degreaser.

This shouldn’t surprise us, as this is exactly how dry cleaners work, and how the older (and better performing) laundry prewashes work.

The reason simply is that if a stain doesn’t wash out, then very often it is because it is oil-based, and so a degreaser will remove it.

So then what’s the difference between these older laundry prewashes and automotive degreasers? Or to put it another way, can you use automotive degreasers as laundry prewashes?

The main difference between them is the washout. Laundry prewashes were designed to wash out completely in the wash, with no residual solvent smell, and are much more sophisticated formulas.

A recent change in automotive prewashes, however, is the switch away from solvent based formulas to water based formulas, based on alkaline silicates. These products of course have no solvent smell and wash out well, and are an excellent option as a laundry prewash.

So use degreasers based on alkaline salts (such as Diggers or Kenco) for general prewashing, and enzyme based cleaners such as White King for food based stains

Laundry Prewashes #4

Another approach to laundry prewashes is oxidation.

This is an approach where fragile, intensely coloured dye molecules such as those in beetroot, red wine and grass are oxidised by an oxidising chemical. In years gone by, this was achieved by bleach. My mother used to get grass stains out of my cricket whites years ago by soaking them in bleach. It worked, but eventually destroyed the fabric.

A more modern approach these days is to use a gentler bleach that will still destroy the colours but not the fabric. This is generally achieved with perborates, compound salts that release hydrogen peroxide, a chemical that is just strong enough to do the job at low concentrations.

There are two laundry prewashes that use this approach – Preen Oxy Action and SARD Oxy Plus. The Preen works the better of the two. In a recent trial I did for Today Tonight of twelve different laundry prewashes, it was the only one that completely removed the red wine stain.

Laundry Prewashes #3

The second type of laundry prewashes are the enzyme based products.

Enzymes are specialist molecules with names like lipase, protease, cellulase and so on. these are large, complex, biological catalyst molecules with very specific chemical reactive properties. In particular, they catalyse the breakdown of fats, proteins, and starches, which are of course mostly found in foods.

For this reason, they are excellent laundry pre-washes for any food stain. there are two products on the market – Coles Ultra Enzyme and White King. The White King product is the better of the two, and will make short work of most food stains.



Laundry Prewashes #2

As it happens, there are four different types of prewashes on the market. Well, three actually if you read what’s on the side of the packaging.

I’m not making any sense, am I? Well, read on and all will be explained.

The first type of laundry prewash are those that are simply water with a bit of soap and fragrance and snazzy packaging. The idea behind these is that you buy the product because the packaging looks so snazzy, and when you spray it on your clothes, you see a bit of foam, smell a pleasant fragrance, and conclude that the product will probably work.

Often, these products to appear to work, but usually only because you have used a premium detergent that has done all the work. If this is not the case, generally you will shrug your shoulders and say “oh well, this type of stain is difficult to remove anyway.”

And, of course, this is pure marketing. Much more work goes into designing the packaging, and selecting the wording to go on to it then goes into the chemical formulation. And this is only possible because we no longer have the “great unstainer” – Preen (the original solvent-based formula).

So will which brands fall into this category? Well, let’s do it this way – rather than embarrass anyone by naming names, in future posts I will name the ones that do work because they have formulas that contain specialised cleaning reagents, and then you can just subtract these from the list that I gave in the previous post, and the ones that are left over are the culprits.

More tomorrow.