Method and Results of Testing Common Wool Scouring Agents

Power Scour Washed Locks

Now that we have the basics and chemical analysis down from our previous post, let’s go over our testing methods and results. With James’ help, we devised a standardized, scientific procedure for this and I performed the tests. We were very careful to keep everything constant and we only changed one variable at a time. Using the same water and apparatus for each wash, we also ensured that the wool used came from the same South American Meat Merino Ram fleece. This boy was exceptionally fine, dense, sticky, and a bit stinky which made him perfect for putting these scours through their paces.

Evaluating Maximum Wash Potential

One piece of data we needed to carry out this investigation was the mass of grease in the raw wool. We used this as an opportunity to test the maximum cleaning potential of each of the scouring agents. To do this we used a very simple wash method. 1.97oz or 56g fiber was placed into a mesh bag and soaked for 12 hours in cold tap water prior to wash. Water of 140F/60C was added to a basin and 3% (by weight of raw fiber) detergent was added. The mesh bag was added into the basin and this was left for 10 minutes to reduce water cooling effects. The bag was then removed and the wash cycle repeated until no more lanolin was evident in the scour bath, which is evident by clouding or opacity of the bath. The rinses were carried out using the same 140F/60C water in the same way as the washes, but without the addition of any detergent. This method was expanded on and will be detailed in the next post clearly.

Raw vs. Rinsed

To begin, the pre-soaked weight of the fiber was calculated. This was found to be 51g, which represents just a 5g, or 8%, decrease in weight from each of the samples. This decrease would be due to removal of some soluble components of the wool contaminants, being mostly suint and dirt. The remainder of the dirt is likely either “locked” in with the lanolin or is lanolin itself, which represents the need for the scouring agent combined with the hot water as we spoke about in the previous post. This did tell us that dirt removal by cold soaking can be useful, but is not entirely necessary prior to scours. The dirt removal is visible in the photo above, but will likely be removed by direct hot scouring without much more effort. However; if you have an exceptionally dirt-laden fleece, cold soaking is going to be very useful. You will see a larger temperature drop taking wool direct from a cold soak and into a hot bath. This can be mitigated doing a hot plain water bath in-between the cold soak and the scour baths. You can take wool from extreme cold to extreme heat safely without felting occurring. The microscopic scales on the wool surface act as a ventilation system, closing when cold and opening when hot. Felting occurs when the hot, open scales intermesh and then are closed quickly with cold or by too much agitation while wet and you should always handle wet fleece with care.

James tends to scour using a given mass of surfactant calculated as a percent of the mass of wool and we worked on developing an easy method with this. One can more accurately determine the right amount of surfactant for the bath type used with this method. Higher percentage of surfactant will generally clean more than a lower percent, but this increase is not always linear, so 2% may not clean twice as well as 1%. 3% for these tests was determined to be an easy, base measurement to go by across the board for our chosen products so that we could really pit them against each other equally instead of following their bottle instructions. Each portion was weighed on a microgram scale to be as exact as we could.

Dawn Ultra, Raw, and Unicorn Power Scour in comparison

Of the results, in fact, the only sample which demonstrated complete grease and dirt removal was that of the Unicorn Power Scour. The remaining weight after scouring was 35g which constitutes a 37.5% change in mass due to dirt and lanolin. Power Scour was also able to remove the contaminants using the fewest washes and rinses, though Dawn Ultra was a close second. We found Dawn Ultra removed nearly all of the lanolin with a small amount trapped in the very tips of the fiber that could be felt when dry. It did leave noticeable amounts of dirt in the wool, constituting a slightly lower mass change of 30%. It also required more washes and more rinses to get to this point, but not by much. You can see the comparison above to note the trapped matter in the fleece tips. Truly, it is not much and we were impressed with Dawn Ultra’s results.

Orvus Paste Max Scour Test Results

For Orvus Paste, even after 9 washes, the fiber still did not show total grease removal as expected, rather removed 21%. For a very low lanolin fleece, this may perform acceptably for you. By far, the number of washes and rinses was greatest though. Orvus also showed a lot of foam which was very difficult and stubborn to rinse out. This is somewhat unsurprising due to the major component being Sodium Lauryl Sulfate(SLS), which is well known to have a very high foam potential. Due to this excessive numbers of rinses and washes for such a poor removal, we chose to eliminate Orvus altogether from the next regiment of tests since it was performing as expected and the next set of tests was about grease removal percentages per bath. Kookaburra, perhaps most surprisingly, was the poorest on performance and we actually could not seem to give the fleece enough baths to remove appreciable amounts of grease no matter which avenue we approached. You can visibly see the lanolin in water as it is very opaque and milky. This was not visible in the Kookaburra baths and we would have spent an exceptional amount of time trying to net a grease-free fleece. As a result, we omitted these results from this table of maximum grease removal entirely.

Water hardness may have been a factor for Kookaburra’s performance problems as it should have net some results based on its chemical make up and this may not have shown it justice. It does take to note, that if you do have exceptionally hard water as the testing water was, this brand may not be the one to go with. Water hardness is well known to influence the performance of many surfactants, especially anionics such as SLS like Orvus Paste uses. Above are the 16 point basic home water testing kit results for the water in these tests. We found that the calcium carbonate level of the well water was 180ppm. In general, water with less than 60ppm can be considered soft, water with 60-120ppm is moderately hard, and water with greater than 120ppm is hard. This could be one potential reason for the poorer performance of Kookaburra and Orvus since they do not contain any softening or chelating agents which would improve their performance under these conditions, whereas Dawn Ultra and Unicorn Power Scour do.

Cleaning Potential Per Wash

Kookaburra Tests

After carrying out the evaluation of maximum grease removal, we chose to investigate the correlation between grease removal and number of washes. To do this, we followed the same procedure as for the washing tests, but removed the surfactant factor after the designated bath number, rinsed as normal, and dried them so that we were able to see the effect of each wash on grease removal. We tested this over 4 different 56g portions per product. Doing this yourself, you may be able to dial in an exact percentage of grease you want to see left in each fleece if your goal is to have some lanolin left in your wools. The below table could also be a good starting point to see those results as well. You can always wash dried fleece with higher lanolin from such tests additional times, so doing this should not net you wasted wool.

The results of the grease removal per scour bath were calculated based on the max scour weight from the Unicorn Power Scour sample in figure 1 (35g). This was most likely as close to totally de-greased as we were able to calculate without lab testing. The grease removal for each sample was then calculated as a percentage of this value.

Instantly from the data, we see that Unicorn Power Scour overall removed the largest amount of grease. It also was able to remove more grease in the first wash than either of the other scouring agents were at approx. 54% removed in the first wash. This is almost comparable in first wash terms to Dawn Ultra which removed 50%. As we discussed, our Kookaburra under performed likely based on our water and you can see it was able to only remove 24% of the grease in the first wash.

Where Power Scour really shows strong performance is in the second wash where it removed a further 30% of the grease compared to Dawn Ultra which did not show a significant increase in grease removal and plateaus quickly. Kookaburra was able to remove only an additional 5% of the grease.

After the second wash, all three formulations showed a small increase in grease removal, and were all relatively comparative. Overall, Power Scour removed a total of 84% of the total grease in 4 washes compared to Dawn Ultra which removed 54% and Kookaburra which removed 37%. This data clearly shows a strong outperformance by Power Scour relative to the other formulations and translates well into the Max Scour Data above. When water usage is in question, Power Scour shows we are using less to accomplish more and when we wash as much fleece as we do here, it is a huge deciding factor. Again, Dawn Ultra showed to be a close second in the Max Scour Data. Below, you can see each sample easily compared between our two main competitors. The 1st, 2nd, and 3rd samples remain quite sticky in each. By the 3rd in Power Scour, we have markedly noticeable difference in feel, and by the 4th in Dawn Ultra.

Power Scour Tests
Dawn Ultra Tests

Speaking of the water usage, we also tested at a later date from these, just how far down we could go in water to wool volume and still maintain the results with Power Scour. Initially, we would wash fleece in nine gallon tubs to one pound of wool. This was of course, physically taxing and having this be easy and accessible is important. Our waste water with Power Scour, since it is largely biodegradable, goes directly into a flower garden as fertilizer and we have questionable plumbing that may take offense to the lanolin being poured down the drain. This is not something we could do with Dawn Ultra, which has environmental toxins. We have seen exceptional results in blooms since we wash so many fleeces. One lily plant went from producing an average of 4 blooms in a year to 18 blooms which was wild and unexpected! However; hauling around heavy nine gallon bins wasn’t the best. Playing with water volume, we found we could reduce it down to three gallons per one pound of fleece with no interruptions to scour performance and it has greatly eased the taxing effort of washing our fleeces.

Discussion of Results

Power Scour at Max

As discussed, Power Scour was able to remove the greatest percentage of total grease followed by Dawn and lastly, Kookaburra. Power Scour’s excellent performance is somewhat expected based on our experiences with this blend, and its formulation. It is mostly non-ionic based, which is very effective at grease removal, and with the addition of anti-deposition agents, which prevent re-adhesion of lanolin to the fibers, it makes sense that more lanolin remains in the water relative to the fibers. Power Scour is also quoted at operating at lower temperatures than the other detergents, hence it is likely that the temperature used corresponds to the optimum temperature for this surfactant blend. Despite being familiar with the product prior to these tests, we were still impressed by how white and soft this very saturated Merino came out and are sure that is evident in how we have been writing about it.

Dawn Ultra at Max

Dawn Ultra is not optimized for wool, but is optimized for grease removal and specifically plant oils and animal fats which contain some of the same component waxes and oils as lanolin. It is unsurprising that the formulation does work to degrease wool, but does not contain the same blend of non-ionic surfactant and rather a higher proportion of amphoteric and anionic. These are shown to not work quite as well in hard water and with the lack of anti-deposition agents it is possible that some of the grease may have re-deposited or some of the surfactant was occupied in chelation with calcium ions in the water. This may explain some of the lanolin feel in the fleece tips. It is also worth noting that the Dawn Ultra example did feel mostly grease-free in the hand despite the lower grease removal percentage. It is possible that the sample of wool used either didn’t contain as much grease, or it is possible some of the grease re-deposited to form a microfilm over the fibers. This is not entirely clear and is very hard to analyze without access to a lab and some different solvents for testing. Overall, this was a very nice and acceptable resulting fiber and a close second to our Power Scour results.

Kookaburra Comparison at 4 scours

Kookaburra, whilst optimized for de-greasing wool, seemingly does not perform nearly as well as Power Scour or Dawn in very hard water. The surfactants used in this formulation are alkyl glycosides, fatty alcohols derived from fatty acids, predominantly. These are well known personal care surfactants and are known to be very mild. However, it is possible that this mildness hinders the cleaning potential. Likely, hard water should have marginal effect on these surfactants due to their non-ionic nature, but we cannot be sure ours did not. It may also be that this surfactant just is not capable of removing higher amounts of wax components, sterols, from wools such as the Merino wool used in this study. We will likely test this again on a fleece that is easier to scour since Merino can be more difficult to scour and we would like to puzzle out the answers here.

Orvus Paste at Max

Orvus Paste definitely performed as anticipated based on its formula with a really decent amount of dirt removal and low grease removal. As stated in our previous post, this formulation is used to wash animals prior to shows, and it does that job well. You don’t want to remove the lanolin off of the live animal as it may cause skin, fleece, and health damage.

As a cost for product analysis between the two products that worked best for us on lanolin removal, at the time of this article, Power Scour comes in at $1.23/fl. oz and Dawn Ultra at $1.71/fl. oz. At max scour by the results here and in the method detailed in the next post, we would have used 4.5fl. oz for one pound of fleece in Power Scour and 5fl. oz of Dawn Ultra. Making Power Scour $5.53 per pound washed and Dawn Ultra $8.55 per pound. A tablespoon, which is the closest standard measurement we will be using, is .5fl. oz, which makes this easy to calculate for your own as well.

In closing, we determined Power Scour is the right product for us, but we hope this data lends some clarity for your own reviews and tests as well. We know that everyone finds a product that they hold dear and works best for them and their home water. We encourage you to do the same methods of experimenting and investigation of your ingredients if you are looking to learn more about your products or scour methods that pertain to wools. This taught us so much and was really invaluable information for how to carry on with our future washing. Finding a way to wash fleece that was effective and easily modified to preference while also taking the scary out of washing wool was so important and I am beyond happy we carried this project through and are able to publish it freely for your use as well. This is the type of skill-sharing our wool communities are so good at and need to grow together. In the next post, we will be sharing the wash method we developed in detail and with plenty of helpful photos to go by. Thank you so much for following along!

Introduction to Common Wool Scouring Agents

In the next series of posts, we are going to go over the results and method that we’ve developed to wash wool in small batches for the home processor. Unhappy with our results by other methods, we set out to find out which scours worked better in our favor and a way to wash wool that depended on listening to your fleece and not the instructions on the bottle. We found too often that we were left with overall sticky fiber, tinged tips, or “pockets” of lanolin left in the fleece where there should be none. This has been quite an interesting series of experiments and fully changed how we approach our wools. Knowing James Perry, also known as LongDrawJames, had his PhD in Sustainable Surfactant Chemistry, we decided to work with him to develop the testing methods and gather his insight. We collaborated on this blog series and below are his writings for the scours we chose to test. None of the materials listed were sponsored and this was a fully unbiased and curious approach.

How Scouring Works

At its fundamental basis, when we scour wool, we aim to do two things – firstly, to remove contaminants such as feces, urine remnants, dirt, and suint (sheep sweat) and secondly, to remove the lanolin. This is an important step in processing wool and very few applications would need lanolin left in the fleece. You should also seek to clean your wools to lengthen the lifespan and ease of use on your processing tools. Lanolin and other contaminants can be incredibly hard to clean off of the teeth of most processing tools. Generally speaking, the suint, or sweat, is made up of salts and other water-soluble organic molecules. Lanolin is a complex natural mixture of greases and oils, containing mostly long-chain triglycerides as well as sterols. Lanolin is naturally water repellent, giving it purpose in aiding the fibers to prevent felting and soaking on the sheep. This means that water alone cannot remove it from the surface of the fibers.

In order to remove the lanolin, we generally employ detergent formulations. Within these detergents, the active chemical compounds which emulsify the grease are called surfactants, a conjunction of surface-active-agents. Surfactants are what are known as amphiphilic molecules, meaning they have a part of their molecule which is hydrophobic, unable to mix with water, and a portion of their molecule that is hydrophilic, which does mix with water.  They are able to lower surface tension between phase boundaries, which means they can allow two liquids which normally would not mix to be granted the ability to mix. Oil and water are a great example. In the case of wool scouring, they allow the lanolin, a hydrophobic grease, and the water to mix.

There are four general types of surfactants and they are named depending on the nature of their hydrophilic group – anionic (negatively charged), cationic (positively charged), amphoteric (both positive and negatively charged), and non-ionic (uncharged). The most important surfactants for wool scouring here are anionic and non-ionic surfactants as these are designed to give optimum performance in the areas we need.

Anionic surfactants are by far, the most widely used surfactants worldwide, making up around 70% of the world’s surfactant use. They are used in almost every single cleaning product. The most common surfactants of this class are Linear Alkylbenzene Sulfonate (LAS) and Sodium Dodecyl Sulfate (SDS), also known as Sodium Lauryl Sulfate. They are mostly used in applications where dirt and stain removal is most important, with LAS tending to be used more in clothes detergents and SDS being used more in personal care as it is much milder to the skin. The major downside of these surfactants in operation is their lack of resistance to hard water. Hard water contains lots of dissolved calcium, which interacts with the surfactants and forms insoluble calcium salts that render the surfactant useless for cleaning. This means you need to add more surfactant than you’d normally need to get the same level of cleaning to account for the amount of surfactant “deactivated” by the calcium. If you are sustainability minded the other major downside of these detergents is their production methods. LAS is produced exclusively from crude oil fractions, and SDS is produced from C12 fatty alcohols derived from palm and coconut oils which have an intensive environmental impact.

Within wool scouring, it is actually the non-ionics which offer the best solutions for lanolin removal as they excel at emulsifying oils and greases. Generally, the most commonly used non-ionics are Nonylphenol Ethoxylates (NPE) and Alcohol Ethoxylates (AE). AE are generally also made from C12-C14 alcohols and a molecule called Ethylene Oxide which is used to introduce the Ethoxylate, a wetting agent and emulsifier. NPE is derived from crude oil. NPE is more of an industrial detergent and is being banned in many countries due to its carcinogenic degradation products and aquatic toxicity. The toxic effects of NPE are a good lesson that biodegradable doesn’t always mean better.

Wool Scouring Formulas on the Market

There are a number of formulations available today as specialist wool scouring agents, as well as some detergents not designed for scouring that people swear by. The four we see most commonly discussed are Orvus Paste, Dawn Dish Soap, Unicorn Power Scour, and Kookaburra Wool Scour.

Orvus Paste is a detergent we see used by many home processors. Unfortunately, it is almost entirely pure SDS. Good for dirt removal, but it has poor hard water stability and does not entirely remove grease. It will do a good job on dirt and is biodegradable, though. Keep in mind that biodegradable is a label that can be put on products even if they do not reach 100% of their materials breaking down in a set timeline. The other issue is its very, very high foaming capacity which means you’ll need a lot of rinses to get it out. Orvus Paste is typically chosen because it is used to wash livestock prior to shows. The use of it to wash the animals makes sense as you would not want to remove the grease from them. Washing wool on sheep in a way that removes their natural oils can cause fleece, skin, and health damage.

Dawn Dish Soap is a formulation specifically designed to clean plates and dishes. It’s a blend of anionic and Amine Oxide surfactants that is often at around 30% surfactant loading in water. In the case of Dawn, the major anionic surfactant is SDS, the same as is found in Orvus Paste. The second surfactant is an Amine Oxide surfactant, which are technically amphoteric, but behave much more like non-ionic surfactants in their cleaning. They are usually very effective de-greasers. In Original Dawn Ultra, or Blue Dawn, you are also going to find some other additives such as a copolymer of PEG and PEI, an anti-deposition agent, as well as Methylisothioazlinone, which is a biocide that can cause acute aquatic toxicity. This makes it not biodegradable. Some formulations contain optical brighteners or enzymes such as proteases which will degrade your wool by breaking it down, so make sure you read the label if you are going to use these. You would not want to get the wrong one and have your wool damaged by it.

Unicorn Power Scour is a formulated blend of surfactants specifically designed for scouring wool. Generally speaking, this is a surfactant blend in water. Surfactants used here are mostly ethoxylated non-ionics which offer best performance for removal of greases, as well as a smaller component of anionic surfactant, which helps remove dirt. Specific identities of these surfactants are not really clarified and it is rather hard to tell which they are using, as there are so many variations which can be sought on the market. The formulation also adds a polyacrylic based copolymer which is a designated anti-deposition agent. This is specifically designed to prevent dirt and emulsified lanolin from depositing itself onto the surface of the wool fibers again and definitely something you want in a scour. Unicorn Power Scour has been labeled and tested to be biodegradable as well, but without knowing what is in the product, we cannot say how much of it is.

Kookaburra Scour is another common formulation for scouring wool. It is also a surfactant formulation in water listed as being natural and plant based. Surfactants used here for de-greasing are almost exclusively fatty acid glycol ethers, which use sugars as the non-ionic group rather than an ethoxylate. This formulation does also contain a very small amount of anionic and ethoxylated detergent and sulfated oil which acts as a surface lubricant.

The Chemistry Behind It

As mentioned previously, the major process which occurs to remove grease from wool is emulsification, meaning the oil and water phases (lanolin and water) are allowed to mix, facilitated by the surfactant. This is not a chemical reaction, but it is a chemical process as the grease itself is not chemically changed by the surfactant.

When a surfactant is dissolved into water, the molecules will remain free in solution. The free surfactant molecules assemble onto the grease using their hydrophobic tails (which are able to mix with the oil). When the concentration becomes high enough, the “pull” of the hydrophilic headgroups by the water is enough that the grease rolls off of the surface and forms a spherical structure known as a micelle. This process is known as the “roll off” method. Generally, people think of micelles cleaning greases, but in the case of detergents this is the actual mechanism of detergency.

The grease has to be fluid enough for the roll off method to work, which is why scouring is carried out at high temperature. The base melting point of lanolin is 120F/48.8C, though it is advised to go a little higher. Likewise, most non-ionic surfactants also work more efficiently at this temperature range.

At a molecular level, this is what is happening when we are scouring wool. But what does this mean on the application level?

Well, when you scour, you need to think of a few different parameters. Part of this is your water temperature, hardness, and volume. You need to have a temperature high enough that you have melted the lanolin. We chose to stick to 130-140F/54.4-60C to truly melt the lanolin and keep the water from cooling between water changes. You also need to consider how hard your water is. Many detergents, specifically anionics are going to suffer from water hardness and you may have to use more than you otherwise might if your water is hard. The bins you use will need to be large enough to accommodate your wool and enough water to give the debris space to gather away from the wool as well. This was all considered for our tests.

What detergent you use is also going to matter. It is generally personal preference as to which scouring agent you use, but we find that one with more non-ionic detergent will de-grease more effectively. We both personally like Power Scour as in our own water situations, which are both, vastly speaking, very hard, this seems to work best. We are also rather fond of the smell and its low foaming capacity that means fewer rinses. Fewer rinses means less water wasted. You will see that it is well reflected in our washing results.

Our next set of posts will be about how we accomplished our testing parameters, their results, and the scouring method that’s been developed. There will be in depth photos for that as well.