Tadelakt Soap by Auntie Clara's

From Tadelakt To the Titanic – How To Use Soap

posted in: Auntie Clara's Blog, Blog Post | 39

A while ago I made some big bars of all-coconut laundry soap. I took some pretty pictures and posted them in a couple of soapmaking groups on Facebook. To my surprise several soapmakers asked the same question: how do you use a bar of laundry soap? Do you grate it or do you just chuck the bar in with the load in the washing machine?

Laundry Soap by Auntie Clara's

I think my surprise at the question really just shows my age, and to some extent my cultural heritage and exposure. When I grew up we always had a bar of un-superfatted laundry soap next to the kitchen sink to remove stains and to wash items that needed washing urgently but weren’t large or many enough to warrant a full load in the washing machine. At the ripe old age of three I decided to wash some dolls’ clothes and I still remember my mom kindly explaining to me that if we want to wash clothes by hand we use the laundry soap in the kitchen, not the bar in the bathroom.

Later on I was taught how to soak blood stains in cold water and then wash the item with laundry soap unless I was doing a full load in the washing machine. I’ve also lived in Africa for a long time now and in African culture washing undies in the washing machine with other garments is often taboo. Instead you are expected to wash your underwear by hand – with a bar of laundry soap. Bars of green laundry soap made from palm oil or tallow are readily available in all supermarkets around here and in addition South Africa has a long and strong tradition of bars of ’boerseep’, un-superfatted all-round utility soap made from animal fat.


Using laundry soap

So how do you use a bar of laundry soap? Essentially you wet the item you want to wash and then rub the bar against the fabric. Depending on the size of the item and how dirty it is you rub more or less. Dip in water, rub, dip, rub, dip, wring, rinse, wring and hang. That sort of thing.

Here’s a rather cute clip of a young Tom Cruise mansplaining to an equally young Nicole Kidman how it’s done.



But for the most part makers of handmade soap tend to focus less on cleaning products and more on ’toilet soap’ as soap intended for use on human skin is known. And most soapmakers will have instructions on their websites for how to look after bars of handmade soap.


Using toilet soap

In contrast to most industrially manufactured, milled and extruded soaps, handmade soap contains glycerine which is a byproduct in the saponification process of oil and lye. Since glycerine is hygroscopic it tends to attract water to the soap. Wet soap wears down quickly so care should be taken to keep handmade soap as dry as possible. Soap dishes should always be draining, i.e. have holes for water to run off. A good way of making sure that soap gets to dry properly between uses is to use several bars in rotation. If a family of four use the same bathroom on a daily basis it’s not a bad idea for each family member to have their own bar; they will probably end up using less soap than if they were to share one continually wet bar, and as a bonus everybody can have their own choice of soap.

Draining Soap Dishes
Draining Soap Dishes

Four soap bars and soap dishes take a lot of space, but luckily there are other creative ways of ensuring that your soap gets to dry even without a draining soap dish.

In my childhood my grandmother had a brilliant, magnetic soap holder. The holder was an arm attached to the wall with a magnet at the end. You stuck a round steel ’cap’ into the soap which the magnet would attract and the soap would then hang suspended from the arm. If I ever come across one of those magnetic holders I’ll get one because they’re very clever.

Our mild and gentle Buttermilk Baby soap has a high olive oil content. Since olive oil soap tends to dry slowly we add a ribbon so that you can hang the soap to dry.

Buttermilk Baby Soap by Auntie Clara's

You can turn any bar of soap into a similar ’soap on a rope’ by making a small hole in the bar with a barbecue skewer or a knitting needle and pulling a string or ribbon through.

Skinny Dipper Floating Soap by Auntie Clara's
Skinny Dipper soap with a cord

Letting the soap dry properly between uses is one aspect of using handmade soap. There are other aspects too which are relevant for the hot question that comes up so often on soapmaking forums:


How long does handmade soap last?

There are some obvious and some less obvious answers to that.

Size does matter so everything else equal a bigger bar can be expected to last longer than a smaller bar. Since most users tend to throw away rather than use the last sliver of any bar of soap, a larger bar will create relatively less wastage than a small bar. But a bar so big that the user is tempted to cut it in half creates as much wastage as two smaller bars.

Shape also matters. A bar with a relatively large surface area (like a thin slice) can be expected to wear down in use quicker than a bar with a relatively small surface area (like a sphere). The rather forbidding, bulky block shape of Mediterranean olive oil soaps is no coincidence: it protects the precious olive oil soap from making unnecessary contact with water. The blocks are not meant to be twirled in your hands in the shower or bath; they’re meant to be rubbed with hands or a washcloth while making as little contact with water as possible.

In addition to shape and size the firmness and texture of the bar is also important. An un-gelled bar dissolves more readily than a bar that has passed through gel phase and a softer bar will wear down faster than a firmer bar, everything else equal. Since water content tends to influence how firm a bar is, a soap with more water will wear down faster than one with less water. This is where the importance of a sufficient cure comes in. As the soap dries and water evaporates the soap becomes firmer and more resistant to wear. As water evaporates the internal molecular structure also changes improving lather etc.

What constitutes a sufficient cure depends to a great extent on how much water was added in the first place. But it also depends on the oil formula used – and the intended purpose of the soap. As I mentioned olive oil soap is slow to dry and so an olive oil soap made with ’full’ water (2.5-3:1 water:lye) intended for regular shower use will have to cure for several months to become firm and lathering enough to be suitable for its intended purpose. On the other hand the coconut laundry soap that I mentioned above gets made with very little water (1.4:1 water:lye) and firms up immediately with great lather. Since the purpose of the laundry soap bar is to be highly cleansing while making very little contact with running water it can be used immediately – even without cure.

In addition to water content the solubility and fatty acid composition (read: oil mix) of a soap has a big impact on how long the soap will last in use. While our coconut laundry soap is rock hard it’s also very soluble and could potentially wear down relatively quickly because of that. This is due to coconut oil’s high content of lauric and myristic acids which make tiny soap molecules – excellent for cleansing. Soap made from tallow (beef fat high in stearic acid) is also very hard but has larger soap molecules, isn’t nearly as easily soluble in water as coconut soap, wears down slowly, and is not as cleansing. Things like mineral content in tap water and in the soap will also influence solubility.

In conjunction with solubility we get to a factor that most ’how long does soap last?’ discussions never touch on: temperature. The solubility of soap in water depends to a great extent on water temperature. Most soaps dissolve much more readily in hot than in cold water. Tallow soap is nicely soluble in boiling water, but not very soluble in cold water. Of all common soaps coconut soap is by far the most soluble in cold water. Again keeping intended purpose in mind this means that the laundry soaps made from tallow by our grandmothers worked well when laundry was boiled in big cauldrons. These days when laundry is done with cold water tallow soaps aren’t as effective as they used to be.

This also means that the water temperature in your shower can have a significant impact on how long your bar of soap will last. If you like to take short, cold showers with handmade tallow soap you might not have to buy another bar of soap for a very long time.. 🙂

Pine Tar Soap by Auntie Clara'sExtra hard and long-lasting pine tar soap made with beef tallow

How long a bar will last obviously also depends on how often it gets used and how much handling and exposure to running water it gets each time. If a family of four takes two showers a day using the same bar of soap, that bar is likely to wear down faster than if one person showers with the soap every two days. If you run the bar all over your body under the shower stream every time you shower you’ll wear down the soap faster than if you only ever rub soap on your hands or a wash cloth when you shower.

So, all in all quite a few factors influence how long a bar of handmade soap will last. And let’s not forget that longevity is a soap virtue with some modification. The longest lasting bars are not necessarily the most pleasant, conditioning, cleansing, or lucrative. Soapmaking is all about striving towards perfect balance and how long the soap lasts is part of that balance.


Other uses for soap

We’ve covered bathroom and laundry use for soap, but soap can be used for a variety of other things as well.

The slippery nature of soap makes it an excellent lubricator. If you’ve ever had a ring stuck on your finger, you’ve probably been able to remove it with a little soapy water. But soap can be used to dislodge bigger items as well.

One of the great South African tourist attractions are the Cango Caves, an extensive underground system of caves and dripstone caverns. Tourists can do the ’adventure tour’ which involves crawling through some very narrow passages deep under ground. A few years ago a rather rotund lady got stuck in a narrow passage and had other visitors trapped behind her in the dark cave for several hours. In the end her rescue by means of liquid soap made the news country-wide.


Soap of Titanic proportions

In the soapmaking community trends come and go and a few years ago many soapmakers had a go at recreating the tallow and coconut ’Vinolia’ soap available to passengers on the Titanic in 1912. But back in the day there was literally a lot more to soap and the Titanic than just Vinolia.

In Belfast in 1911 when the hull of the Titanic was launched and touched water for the first time, the slipways had been well lubricated. 15 tons of tallow, 5 tons of tallow and sperm whale oil mixture and 3 tons of soft soap were used to help the massive hull slip into the ocean. The soft soap helped keep the whale oil and tallow mixture together.

Titanic Slipway
The Titanic seconds after launch. The snowy white line to the left, next to the girls in white dresses and big hats is the slipway covered in a thick layer of tallow, sperm whale oil and soft soap. Photo courtesy of the Daily Mail, UK. http://www.dailymail.co.uk/travel/travel_news/article-3279035/Haunting-never-seen-photographs-Titanic-s-launch-auction-Incredible-images-doomed-ship-sliding-water-Belfast-shipyard.html


Before the advent of petroleum grease, animal fat and soap were standard lubricants in shipbuilding and shipyards were major soap users. Soap companies like Swedish Fabriks AB Victoria, now known as Victoria Scandinavian Soap AB and famous for their egg soap, produced large quantities of soft soap for the shipbuilding industry in the 1930s. The volumes were staggering with up to 5 tons of soap being used for the launch of one vessel.


Fish Food

Ships are intended to float on water but there are some interesting and unusual underwater uses for soap too. Apparently soap can be used as fish bait and cat-fish in particular are said to be partial to natural soap. Fragrances and flavours being mentioned as favoured by fish are aniseed, garlic and canned corn juice. I can only imagine that a little bit of tuna brine or sardine oil plus a side order of dried shrimp could make a nice addition. To date I haven’t tried this myself, but I might give it a shot next time I know I’ll be doing some angling.


“The smell of Napalm in the morning”

Less wholesome or inspiring is the use of soap in the original version of the sinister fire-bombing substance Napalm. Napalm gets it’s name from the first syllables in naphtalene and palmitate. Palmitate in this case is the soap aluminium palmitate, an aluminium salt of the same palmitic acid widely used in toilet and laundry soaps. Aluminium palmitate was used as a thickening agent making the Napalm viscous and sticky. Modern day Napalm is made with a different formula.

Aluminium soaps have been used in more constructive contexts too. In the days when tents and anoraks for the great outdoors were still made of cotton fabric they had to be waterproofed. My mother was a great believer in waterproofing cotton fabric with a solution of alum and ordinary laundry soap that you dipped the fabric in and then let it dry. According to her this alum and soap treatment didn’t only make tents waterproof, it also made the fabric resistant to burns from campfire sparks. The fire resistance I haven’t checked, but I’ve come across several recipes for waterproofing textiles with alum and soap.



Finally, waterproofing leads me to the technique and fine art of tadelakt.

In a comment to my 2014 blog post about beldi soap which you can read here, fellow soapmaker Eileen Wosnack mentioned a plastering technique involving soap. I hadn’t heard of any soapy plastering techniques so I was intrigued and decided to do a bit of research.

This is what I learnt: In Morocco where beldi soap (aka black soap or savon noir) – a soft potassium, olive oil, and olive paste soap – is used for skin care in hammams (bath houses), the same soap is also used to waterproof plastered walls, floors and water cisterns. This centuries-old technique is called tadelakt.

A paste is mixed of slaked lime (calcium hydroxide), water and an aggregate like marble dust or fine sand. This plaster is applied to a substrate in either one or two layers and the surface is smoothed with a wood or plastic trowel. While drying the surface is compacted and burnished with a smooth rock, typically a hard, semi-precious stone. Once the surface is smooth a solution of water and beldi soap is applied, and the surface is again burnished with the rock.

The soap reacts chemically with the lime plaster speeding up carbonation of the surface and forming insoluble calcium soap which makes the plaster waterproof and water-repellent.

Does this sound vaguely familiar?

If you’re a soapmaker it should because the chemistry is the same as for soap scum; that opaque and pesky ’crust’ that gradually forms on the walls of your shower when soap (sodium salt of fatty acids) reacts with calcium in your tap water.

To me it sounded almost too simple to be true, but quite enticing and ingenious. And needless to say it was something I wanted to try myself. But the months piled up and became years and I never got around to it.

Then one day recently ago I decided to go ahead and finally give tadelakt a go.

First things first so I started by making a special tadelakt soap. Since using beldi soap on your skin involves both vigorous rubbing and leaving the soap on the skin for a while I usually make beldi soap for skincare purposes with a generous superfat. The desired chemical reaction for tadelakt requires hydrolyzed fatty acids though rather than oil, so I made the tadelakt soap without superfat.

Tadelakt Soap by Auntie Clara's

I discovered that my neighbourhood building supply store carries slaked aka hydrated lime (calcium hydroxide) – in handy little 25kg bags. I wasn’t going to do any large surfaces of tadelakt so 25kg was decidedly excessive for my experiment, but on the other hand I also discovered that slaked lime is cheap and so I lugged home a life-time supply of slaked lime.

Next I needed sand. My ever-friendly and helpful neighbour Amanda was having building work done to her house and so I borrowed a pail of building sand from her. I sifted the sand through a strainer to eliminate the biggest rocks.

Now I had all I needed apart from a suitable substrate. One tadelakt website suggested covering a cob ball in tadelakt for a first project. Balls I can muster if pushed but no cob so I went to my friendly discount tile store and asked for some scrap tiles instead.

Backside of a tile waiting to be covered with tadelakt
Backside of a tile waiting to be covered with tadelakt

Armed with soaping goggles and gloves (slaked lime has a pH of 12+ which means it’s caustic and can cause severe discomfort if you e.g. get it in your eyes) I mixed a soft paste from roughly equal parts (volume) slaked lime and fine sand plus a little water. At this point I could have added pigments for colour, but I decided to keep it as simple as possible to see what the actual colour would be like.

Tadelakt plaster
Tadelakt plaster

In the early morning of day one I rubbed the plaster onto the backside of my tile, making a thin layer just thick enough to cover everything. After that I smoothed the surface with a plastic ’spatulator’ thingy from my soap utensil drawer.

First layer of tadelakt plaster applied to the backside of a tile
First layer of tadelakt plaster applied to the backside of a tile

I left the house and got back to apply a second layer of plaster about 5 h later. Again I smoothed out the surface trying to get it as flat and even as possible.

(If you’re a plaster master, please be gentle here and consider that save for using Polyfilla to fill holes in walls on three continents, I’ve never done any plastering before this. Also, my objective here wasn’t to achieve maximum adhesion to the substrate, but to see if I could create a water-repellent, waterproof surface.)

After a couple of hours the surface was dry enough to handle. That’s when I started compacting and ’tightening’ the plaster in small circular motions with a plastic bottle cap. Loosely translated the word ’tadelakt’ means ’to rub in’ and you certainly get to do a lot of rubbing in with this technique.

Plastic bottle cap for initial compacting of the tadelakt.
Plastic bottle cap for initial compacting of the tadelakt.

When the surface was so dry and hard that the plastic from the cap started wearing off onto the plaster I switched from the cap to a polished semi precious stone that I borrowed from my daughter’s stone collection.

Pretty rocks for burnishing tadelakt
Pretty rocks for burnishing tadelakt. The red rocks, whatever they are, were too soft for the lime plaster and left red streaks on the surface. All the other ones worked well.

Again I went over the entire surface a good few times with small circular motions applying gentle pressure as I went.

Tadelakt surfaces are said to be ’hard as stone and soft as silk’ and my little tadelakt tile was well on its way to becoming just that. Burnishing the plaster surface with a hard stone really makes it beautifully glossy with a perfectly smooth, silky feel. You just want to keep running your fingers over it because it feels so nice.

Burnished tadelakt prior to soap treatment
Burnished tadelakt before soap treatment

In the evening of the first day I gave my piece of tadelakt its first ’soap massage’ with a solution of my un-superfatted tadelakt soap paste and water. The solution needs to be saturated with soap but still be quite liquid since the soap is meant to be absorbed into the plaster rather than sit as a layer on the surface. With the plaster wet with soap solution I once again went over the surface rubbing it in tight circles with the stone.

Beldi soap solution applied to tadelakt plaster
Tadelakt soap solution applied to tadelakt plaster
Soap solution in the process of being rubbed into the tadelakt plaster
Soap solution in the process of being rubbed into the tadelakt plaster

On the morning of the second day I gave the plaster a second soapy massage with more soap solution and the burnishing stone. As the moisture was absorbed and the surface dried I buffed it with some washed wool and then left it to do its own thing for the rest of the day.

Soap-treated tadelakt in the process of drying
Soap-treated tadelakt in the process of drying

Tadelakt can take several weeks to dry completely, but not being equipped with any excessive patience, I decided to give my tadelakt tile a little test run on day three, 24h after the second soap treatment. Lo and behold, as I poured water on the tadelakt it stayed in perfect droplets on the surface, running off nicely without being absorbed into the plaster! I’m expecting the tadelakt will continue to dry and harden over time but I think it’s so exciting that it worked and that I had been able to make actual, real tadelakt!

Water resting on the water-repellent surface of tadelakt plaster

But even more interesting was the fact that despite all the soap that I had worked into the plaster there was no soapy feel to it at all when I poured water on it a day later. No soapy slipperiness or shy bubbles as I wiped off the water. Just water on a rock hard, silky smooth surface..

Having great passion for soap I’m in awe of the tadelakt process, its history, its chemistry, its possibilities and its beauty. The process is highly labour-intensive and artisanal but the polished end result from natural raw materials is simply stunning.

So, there you go. Soap is so much more than just a bar in your bathroom. Soap is versatile and there are plenty of interesting ways that soap is and has been used – many more, no doubt, than those I’ve mentioned here.

And if anybody in this neck of the woods needs a little calcium hydroxide I’ve got about 24.5 kg to spare.. 🙂

Tadelakt Soap by Auntie Clara's
Tadelakt plaster and tadelakt soap on tadelakt surface

39 Responses

  1. Amanda Venceslau

    Hi! I love reading your posts, your thoughts and ideas! Love your pictures too and your soaps are beautiful I love how you join history with culture and how you explain it all

  2. Navajo

    You are wonderful for sharing. I have heard of this in the ‘states’ (U.S.) for very high end homes. Thank you so much.

    • Clara

      It’s a pleasure. In most cases tadelakt is likely to be a high-end finish because it’s so labour-intensive. But the raw materials are simple and inexpensive. With a growing interest in sustainable, natural and environmentally friendly options I think we might hear more about tadelakt in the future.

  3. Danica

    Your post are always highly interesting! Thank you so much for taking the time to show us what you are doing. All the best to you!

  4. Lisa

    I really enjoyed this post, I like that you address different functionally of soap and uses that don’t really occur in the cosmetic departments. I loved the picture of the colorful soap dishes, I know I can keep all the bars I like to use dry. Then there is tadelarkt which is surely a learning experience for me thank you!

  5. Adrienne

    Hello Clara,
    really enjoyed your post as usual. I also remembered the magnetic soap holders of my childhood and how useful they were, so I did some research. I have had all my handmade soaps hanging onto them for several years now. They are available from a company called ZACK, mine is called “MARINO”. They are hardy, made of 18/10 INOX stainless steel, not beautiful but actually quite neutral (at around twenty-five euros each, not cheap but I think it’s worth it). If they are not available to you in South Africa maybe your European family can get hold of them.
    All the best to you and yours.

    • Clara

      Thanks Adrienne, I must look into that. So glad to know that they are still being made because the concept is really good.

    • Clara

      Thanks Katie! I just watched that clip and it’s so cool! Quite interesting to think of soap being used as an altenative to various palstic and solvent based products. I can see how this would make a beautiful floor finish; because it’s soap you end up removing dirt too each time you re-apply the soap.

  6. Judy

    Very interesting! Great how you keep reviving old techniques. Traditional methods are not always keep alive. My Mother always had a hard bar of Sunlight soap at the sink in her laundry room. She swore by it!

    I really enjoyed this article. Hopefully, someone will relieve you of the calcium hydroxide!

  7. Debi Olsen

    Such an amazing experiment, Clara. Thank you so much for sharing it! Your adventures are always so enlightening and a joy to read about. Thank you!

  8. Jane Campbell

    Hi Clara! The confusion about laundry soap made me laugh! Did people seriously think to put a whole bar of soap into a washing machine!!?? Very interested in the different uses for soap you discussed, and also, my father was a plasterer, so I was interested in the tadelakt waterproofing. How incredibly labour intensive – let’s hope they are only doing small bathrooms!

    • Clara

      Apparently outside walls are also sometimes done in tadelakt. You’re right in that it’s labour intensive – but so is going to the gym if you think about it 🙂

  9. Eugenia

    You should take part in a contest for one of the best blogs on the internet.
    I most certainly will highly recommend this site!

  10. Helene Galabuzi Gjelsås

    Hi Clara!
    Thank you for your tadelakt experiment! I found your webpage by googling for tadelakt and soaps, because I have a hope of trying it out, but I don’t have access to olive oil soap. I am Norwegian, but we are building in Uganda, and have lots of those soap bars! I am not so into the soap chemistry, though. Do you think I could try one of them? Or are they to fatty/unfatty/soponified – I am not familiar with these terms…
    Best wishes to you!

    • Clara

      Hello Helene!
      I checked out your building video on YouTube – very impressive! In answer to your question I’m not sure that ordinary bar soap is going to work as well as soap paste. Bar soap is a sodium (natrium) salt whereas soap paste is a potassium (kalium) salt. Sodium salts are less soluble in water than potassium salts with a tendency to solidify whenever possible. Potassium salts will stay in solution with water. For Tadelakt the result of this could be that potassium salts are better able to bond with the substrate making them more effective.
      However, I don’t think that it’s particularly important that the soap paste is made from olive oil. I’m sure potassium soap paste made from another oil could work just as well. In the Nordic countries we have traditional soap pastes made from hemp oil (grönsåpa) and tall oil (gulsåpa) which probably work just as well as olive oil soap paste. If you can find soap locally that’s made the traditional way with lye from wood ashes (potash) that would be a good approximation of traditional beldi soap. Or just try regular bar soap and see if it gets you a waterproof finish. The important thing is that you use actual soap and not some synthetic surfactant since synthetic surfactant isn’t likely to form the bond you are looking for.

      • Helene Galabuzi Gjelsås

        Great!! Thank you very much for taking time to explain! This was very useful. We will look for local products, and now I know what to ask for. As I am in Norway now, I could even make a little test with Grønnsåpe.
        And thank you for your compliments to our building project!
        Best wishes!

  11. Angel Dobs

    Hello Clara,
    Being raised on a farm, where water from the well was our only source for a family of 14, you develop a lifelong respect for conservation. We bartered our handmade soap with others who farmed commodities we didn’t, such as cows and pigs. I enjoy reading your blog, and YES there is always a piece of coconut laundry soap next to my bathroom sink for laundering miladies dainties and spot treatments for quick stain removal. My grandchildren call it “Grandma’s Super Stain Removal”. Bless them, they believe Grandma can fix anything.

  12. Bernardo

    Dear Clara,

    I have been making my own olive oil / coconut oil soaps since last year, and I was puzzled with the fact that they were always melting down after some use. I thought I was doing something wrong, thank you for clarifying that it is due to the high glycerine content! A question: for tadelakt, what would be the best soap I can make? hard or liquid? i..e., made with KOH or NaOH? superfatting or no? I am very interested in tadelakt, in fact it was the reason I started making my own soap, but I can’t find this information anywhere. Best regards from Rio!

    • Clara

      KOH is what traditional tadelakt soap is made with so I would go with that. KOH soap is more soluble in water than NaOH soap and may be more readily absorbed by the plaster.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.