The Chemistry of Clothes Washing #10. Liquid Detergents

No discussion of laundry detergents is complete without discussing liquid detergents.

It’s probably fair to say that liquid laundry detergents play second fiddle to powdered detergents.  Having said that, this is probably based more on perception than performance, with many people thinking that when you buy a liquid detergent you are paying for a lot of water.

This is of course partially true, but not to the degree you may think.  Whereas dishwashing detergents are between 80 to 90% water in general, laundry detergents are typically around 50 to 60%.

Liquid detergents generally use non-ionic surfactants rather than anionic surfactants, which doesn’t mean much in terms of cleaning other than that they tend to be a little more versatile in terms of their stain removal properties.

The two standout performers in terms of liquids are Dynamo and BioZet, for different reasons.  Whereas the BioZet (which also comes in a powder) is a largely enzyme-based product, the Dynamo is a very sophisticated formula where they have managed to suspend material in the liquid that is not normally liquid soluble, which gives the liquid an opaque appearance.  Technically, this makes it a suspension rather than a solution, but let’s not go into that for now.

Specifically, Dynamo has managed to suspend perborate and percarbonates materials in their (laundry bleaches), as well as adding a sophisticated enzyme matrix.

Also, liquids have the advantage of providing a prewash capability.  That is, if you had a particular stain, you would just rub a bit of the liquid into the stain before putting it in the wash.  If you tried the same thing with a powdered detergent, you would get fluorescent burns in the material (from the fluorescing agents).

And, of course, you do not need to worry about solubility of the liquids, so they are certainly a good option for cold water washing, if that’s what you wanted to do.

Another interesting market trend that has occurred in recent years is that for many of the brands on the market, they are available as both liquid and powder, which did not used to be the way things were.  It used to be the case that if you wanted a powder you bought one brand and if you wanted a liquid you bought another brand.

Oh, and here’s a final tip if you are using liquids.  One of the most annoying things about liquid detergents is that if you use the cap to measure out the liquid, then it makes a mess when you put it back on the bottle.  A simple solution that I have used when I have used liquids is that you simply toss the lid in with the wash.  Retrieve it afterwards, and it’s nice and clean so it doesn’t make a mess when you put it back on the bottle.

Okay, tomorrow I will summarise things and go through a few common mistakes that people make.  Then we’ll start looking at pre-washes.

 

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.

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

The Chemistry of Clothes Washing #7: Enzymes

Without question the most exotic chemicals in any laundry powder are the enzymes.

Enzymes are chemical specialists.  If they were people, they’d be neurosurgeons or paediatric gastroenterologists.

Each enzyme has a particular thing it is very good at.  The first product to use enzymes on the market was NapiSan, which used enzymes that could even remove blood, which was virtually impossible up to that point.

So the inclusion of enzymes in laundry detergents involves using chemicals that target very specific types of stains.  Normally these are just one component of a premium brand detergent, but BioZet have taken a whole new approach, in that they market a detergent in which the cleaning power is almost entirely enzyme – based.  That is, they make a big thing out of the fact that they contain no bleaches or fluorescing agents, and only a mild surfactant base.

In their place, they have a blend of specialised enzymes which, we are told, work very well.  I haven’t tried this myself (perhaps others can report) but the idea certainly seems sound in principle.

But enzymes have another role.  White garments, particularly cotton, tend to take on a yellowish hue after a while.  This is caused by tiny cotton fragments breaking off and pointing up in the air.

This has the effect of scattering the light as it hits the garment, resulting in a yellowish colour.  Enzymes are able to attack these little cotton strands (the term is “pilling”) and remove them.

This restores be white colour to be garment.

Incidentally, when enzymes were first used, and their first big scalp in terms of recalcitrant stains was blood, they once caused a bit of a problem.

There was a particular brand (it may have been BioZet but I am not sure) that in their advertisement on TV showed little Pac-man type creatures going around gobbling up blood, the message of course being that this product could remove blood stains.

What they hadn’t accounted for, however, was the workers in the factory who packed this stuff.  They saw this and and quite reasonably thought to themselves “wait a minute – if this stuff eats up blood, what is it doing to us – we work with it every day.”

This resulted in a strike, which wasn’t resolved until the workers were reassured that there were no health risks involved.

Okay, that’s pretty much it for all the individual components of laundry detergents – tomorrow I’ll pull it all together.

The Chemistry of Clothes Washing #6: Bleaches

There are several approaches to stain removal.

One of them is to destroy the stain.  That is, if you are unable to remove the stain from the garment, you destroy it where it stands.  That’ll learn it!

Now, in this sense buy “destroy” all I mean is that we have to alter one part of the molecule so that we can’t see it any more.  Most food-based stains are dyes, which are large complex organic molecules.  To alter the molecule so that it loses its colour, the easiest approach is simply to oxidise it, and this is where bleaches come in.

By “bleach”, we are normally referring to swimming pool bleach, sodium or calcium hypochlorite.  But, in fact, the term “bleach” is a generic term, and refers to any chemical that can have a whitening effect.  In this sense, it is referring to oxidising chemicals.

Swimming pool bleach is a very useful chemical as it is just about the strongest oxidiser in existence (which makes it a great disinfectant) but also because it is very cheap to make.

Unfortunately, because it is so aggressive, it’s a bit over the top when it comes to use on clothes, as it tends to destroy them.  I remember my mother used to clean my cricket whites in bleach, and they didn’t last long.  The material in the pockets fell apart first, followed by the rest of the garment.

In this sense, synthetic fibres are more resilient, and will cope with bleach more so than natural fibres, but it’s still not a good approach.

This is why laundry detergents contain gentler bleachers, and these are perborates, percarbonates, and (more recently) peroxides.

These have a more gentle oxidising effect on the stain then the chlorine bleach does.  The use of peroxides are a more recent addition, and I think this is what is referred to by the phrase “active oxygen” that some Reckitt Benckiser products are now advertising.

Peroxides fall between chlorine and the other bleachers in terms of strength.  They are not as aggressive as the chlorine is, but are more aggressive than the perborates and percarbonates.

Laundry bleachers are and integral part of any premium washing detergent, and tomorrow will will look at another one – enzymes.