The Myth of Detergent Buildup

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by Cecily Jordan

One of the most prolific cloth diapering myths is that of detergent buildup.  This is the primary reason given for using tiny amounts of detergent to clean cloth diapers and is often blamed for stink and rash issues.  Unfortunately, the fear of this supposed buildup, and the subsequent use of too little detergent as a way of avoiding it, are what often lead to stink and rash issues in the first place.  Fortunately, we can explain why this is a myth, and you can feel safe using a normal, appropriate amount of detergent to clean your cloth diapers!

This is a great place to start when trying to understand the components of laundry detergent and how the detergent actually works:

The History of Laundry Detergent

It may seem like it doesn’t matter, but knowing why laundry detergent was invented is actually really important in understanding why detergent buildup is a myth!  The forerunner of laundry detergent as we know it today was introduced in 1916.  It was developed as a result of the shortage of fats and oils during World War I.  Before that people used soap for everything, including washing their laundry.  But because the materials used to make soap were becoming scarce they needed a new substance that could be used to wash clothes in less than ideal water conditions, like seawater or cold water, and would not combine with the minerals in water and create a scummy, water-repelling substance called soap curd.
(For the record, the problem of scummy buildup is still an issue when soap is used to clean fabric, even today!   That’s why it’s important to avoid using soap to wash laundry.  It is not designed to rinse clean from fabric.  It’s also pretty likely the idea of buildup occurring on clothes as a result of washing them springs from this exact phenomenon – it’s an old holdover from the days when soap was used to wash laundry!)

In 1946 the first detergent containing surfactants and builders was invented, and that is the most relevant development of all!  Today’s detergents still use the surfactant/builder combination because it is extremely efficient when it comes to removing soil from fabric and when it comes to rinsing out clean.  How it all works will be explained in detail below.

The Difference Between Residue and Buildup

“But if detergent doesn’t build up then why am I seeing suds in the water during my rinse?”
It’s important to make the distinction between residue and buildup.  Think of it like a snowball rolling downhill in a cartoon.  If the snowball were detergent buildup, the snowball would simply continue growing larger and larger as it went until something major happened to break it up.  If the snowball were residue, on the other hand, it would be kept in check by the warmth of the sun, so even though new snow would be added, some snow would also be melted away before more new snow was added.
So basically, for it to be considered buildup it would have to accumulate over time, with nothing ever washing away before more was added.  Residue, however, will be present but will rinse away with the next wash before anymore residue is deposited.  Keep in mind that some detergents have components that are designed to stick around in fabric after the wash is through, and these components may appear as a small amount of suds in water that’s been agitating.  Don’t worry, unless you’ve got a thick layer of sudsy foam fluffing up on top of the water, you are not seeing an excess of detergent.  (And if you do have that, there are a couple of reasons why that could be, and none of them have to do with detergent buildup!  Ask our admins for advice on what to do in that situation!)

Common Detergent Components and Why They Don’t Build Up

Surfactants are molecules with a hydrophilic (water loving) and hydrophobic (water repelling and oil/dirt-loving) ends.  The hydrophilic end clings to the water molecules, while the hydrophobic, dirt-loving end grabs onto the soil in the fabric.  Because the water is spun out of the drum and the clothes stay put, the dirt and grime leaves with the water, thanks to those hydrophilic parts of the surfactants.  That’s how we know that the detergent is rinsing out of the fabric – it isn’t interested in staying in the fabric, it is chemically structured to cling to the water!

Builders are added to some detergents to allow the surfactants to work better in hard water. We know them better as “boosters,” and those of us with hard water are even adding more when we toss in, say, borax, with our laundry. Simply put, they work by binding to the junk that makes water hard, both keeping it out of the fabric and by taking care of the minerals in the water so the detergent can focus on the soils from the fabric. These builders, or boosters, are like the detergent in that they’re more interested in what’s in the water than in the fabric of the clothing. They drain with the water.

Optical brighteners are added to some detergents to combat the natural yellowing of white and lightly colored fabrics over time. This is kind of an easy one to avoid if you want to because lots of detergents don’t use these since some people have sensitivity to some kinds of brighteners (there are a handful of different kinds used). At any rate, they work by using fluorescence to give fabric the appearance of being “whiter than white.” They may also be referred to as dyes, because they technically are, though they appear invisible to the naked eye. According to my research, a very small amount is put into the detergent to begin with, and while it does have a cumulative effect over time it doesn’t cause repelling or scummy buildup. Essentially, it’ll make your diaper inners shine under a blacklight but it won’t stop them absorbing liquid.

Enzymes have been discussed extensively lately, they get a pretty bad rap. Enzymes are naturally occurring, biodegradable, and extremely effective because they do such specific jobs and can do those jobs without being destroyed or “used up” in the process. A small amount is used in detergent to act as catalysts to speed up the process of stain removal and the breakdown of various types of spots. The enzymes basically munch on the junk in the fabric and remove it. They also rinse out pretty effectively, though if they do remain present they neither destroy fabric nor eat skin. There’s no indication that they build up in fabric either.

Fillers dilute detergent, so they’re not helping it build up.  In liquid detergent the filler is typically water.  In powdered detergent it’s often sodium sulfate.

Fragrances. There are so many different scents used in detergents, it’s pretty much impossible to figure out who’s using what to make the fabric smell like it does, but there’s no indication that the scents themselves are causing any kind of buildup. They obviously stick around, but they don’t cause repelling. Some people are allergic, so that’s a good reason to avoid if necessary. The only thing that’s going to alter the smell of the fabric AND cause repelling is fabric softener.

You can check also out our file all about detergent ingredients.

The bottom line is that the concept of laundry detergent has always been that it would not cause buildup, and indeed today’s mainstream laundry detergents are all formulated with that powerhouse surfactant/builder combo that means they rinse out very effectively, every time!  If there is residue left behind it’s very little and does not have a cumulative effect.  Yes, detergent buildup is a myth!

However, it is possible for other things to build up in diapers. Ammonia, which forms naturally from urine, can build up in diapers as a result of old urine not being thoroughly cleaned out of the diapers.  Contrary to popular opinion, it’s actually the result of not using enough detergent, not the result of a buildup of detergent.  The longer an ineffective wash routine is used the more ammonia there is being added to the diapers, until it’s enough to make your eyes water at the first whiff, and to burn your baby’s skin.  Once diapers have reached the point of causing ammonia burns, it is necessary to neutralize the ammonia and sanitize the diapers.

To avoid ammonia buildup in the first place is very easy – simply maintain a proper wash routine using enough detergent to get your diapers clean!  If you need to change your routine and aren’t sure where to start, see our page on how to wash cloth diapers.

Additionally, diapers washed in hard water can develop a buildup of minerals, which are deposited by the hard water into the fibers of the diapers every time they’re washed unless an additional booster (such as Calgon or borax) is used during the wash cycle.  Mineral buildup can also trap bacteria, causing barnyard stink and rashes, and can also trap ammonia and facilitate its buildup as well.  Learn about washing in hard water.

It’s important to know whether or not you have hard water!  See our page on what to do after you’ve done a water hardness test.

Diapers with mineral buildup from being washed in hard water will need to be stripped and sanitized.

And those with hard water who are just getting started with cloth diapers, or those who’ve just recently had to start washing in hard water need not worry!  Follow the instructions outlined for properly washing cloth diapers in the file linked above and you should not need to worry about mineral buildup to begin with.

In the end, there’s no need to worry yourself over buildup at all as long as you have a good, solid wash routine and use a well-formulated laundry detergent. While it can be quite scary to go against advice that’s so widely circulated, the benefit of trusting in the specialized formulation of mainstream detergents is that you free yourself from the burden of excessive and ineffective wash routines, and your baby from the risk of persistent rashes.