Oval Soap by Auntie Clara's

Oh So Oval – Oval Soap Mould Tutorial

posted in: Auntie Clara's Blog, Blog Post, Tutorial | 100

My fascination with oval soap began when I was nine and my parents took us on a trip to Zanzibar. From that trip I remember seeing cinnamon trees and smelling fresh lemongrass for the first time and I remember walking through narrow streets in the late afternoon and taking in the amazing fragrance in a little square where fresh cloves had been laid out to dry in the sun.

Yet, for Auntie Clara’s later soapmaking exploits none of that was as significant as the souvenir that my father somewhat hesitantly but kindly bought me. Tucked away in a dark and dusty corner in a bric-a-brac shop in Stone Town I found a treasure: a little ancient-looking oval cardboard soap box large enough to fit one 100g bar of soap. As you lifted the purple, black and silver lid, the oval box was full of shiny golden seed beads and glittering sequins in all the colours of the rainbow. The box still had a vaguely perfumey smell, but mostly it had a reassuringly old smell. Old cardboard, old dust, old drawer and old memories.

To my nine-year-old imagination that box and its contents represented a key to a mysterious, golden, romantic and glamorous past of unknown, but undoubtedly interesting characters. What had the fancy oval soap looked and smelled like, who had used it and for whose beautiful ball-gowns had the beads and sequins been intended? Inspiration for hours and hours of fantasy – and my first crush on fancy soap packaging.

Now the box with beads and sequins are long gone and no matter how I google I can’t find an image of a similar one anywhere. I’m not sure what the fragrance of the soap might have been – judging from the purple on the lid it could have been violet – or lilac. The box must have had some kind of writing on it but that obviously made very little impression on me because I can’t remember it. However, the oval shape of that box with its embossed finish has stayed with me through life and to this day I love an oval bar of soap!

Lavender Heart Handcrafted Soap by Auntie Clara's
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Fleur de Lys Handcrafted Soap by Auntie Clara's
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Oval is a great shape for soap. It’s visually appealing and it mimics the shape that soap in use gravitates towards – all sharp corners smoothed out and fitting perfectly in the hand for pleasant grip and easy twirling. There’s something nicely old-fashioned yet eternal about oval soap. It feels great to hold and it’s practical too, since unlike a round bar, an oval bar can be placed on its side without rolling off on unauthorized adventures.

Pine Tar Soap by Auntie Clara's
Green Eucalyptus Handcrafted Soap by Auntie Clara's
Green Eucalyptus Handcrafted Soap by Auntie Clara's
Milk & Honey Soap by Auntie Clara's

 

It’s not impossible that my soft spot for ovals in general is inherited. Legend has it that when my father first introduced himself to my mother he offered her some aniseed bonbons. Those same bonbons still come in a pretty little oval tin..

Violet flavoured anise bonbons
Violet flavoured aniseed bonbons from Flavigny

 

When I started making soap one of the first things I did was look for oval soap moulds. The little oval silicone friand moulds I already had in my kitchen were soon re-purposed as soap moulds and while my better half with his big hands feels that they are the perfect shape and size, I wanted something that would make slightly larger bars.

Being a big DIY enthusiast I was keen to make oval moulds myself – with materials I could source locally. What I could source locally was PVC pipe, and a little googling revealed that round PVC pipe could be heated and re-shaped to make it oval. Sounded simple enough and soon I had my first vertical oval mould. I have since made many more and this is how I do it.

 

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First the pipe. I use heavy duty PVC pipe with a wall of approximately 3.5mm thickness. Outflow pipes are typically made with this kind of pipe since the thick walls make it relatively heat resistant. Heat resistance is a handy feature for a soap mould since soap can get fairly hot.

The caliber of the pipe is obviously a matter of personal preference. I’m always partial to a chunky bar rather than a thin slice so I like to use 75mm pipe and make thicker cuts, but you could use any caliber you like.

How long you want your pipes depends on the size of your oven – and your freezer. Since you are using the oven to heat and reshape the pipe it needs to fit in the oven. Later on, in use, you want to be able to freeze soap in the pipe for easy unmoulding and so the pipe needs to fit in the freezer too. I have a small oven and a narrow freezer so I’ve cut my pipes fairly short.

How you cut the pipe is important too. In use the pipe will be standing on its end, ie you want it cut at a right angle for the pipe to stand straight. The cut itself needs to be as neat and smooth as possible to make the seal at the bottom as tight as possible.

_DSC0342My friend Mike who is a gold mine of technical knowledge, out-of-the-box thinking and heavy duty power tools, was kind enough to cut this pipe for me.

 

Then the oven. For my heavy duty 75mm pipes I find that 15 min in a preheated 120°C oven is just right. That will soften the PVC just enough to make it pliable with enough resistance not to collapse on itself. Note that heating PVC releases unhealthy fumes so make sure to clear your kitchen of pets, children and pregnant ladies for the duration of this exercise, keep the extractor fan running and open doors and windows for maximum ventilation. Wearing a mask with an appropriate filter is a good idea. Have gloves handy because the pipe will be hot to the touch when you remove it from the oven.

Once the pipe is hot you’ll need to press down on it to flatten it to an oval shape. How much you flatten it will decide what shape the bars will have. It’s very important to press down evenly along the length of the pipe. If you flatten one end more than the other or if you make dents halfway, the soap will never slide out of the pipe.

For pressing down I use a plank that’s longer than the pipe. To make sure that I press down evenly on the pipe – and that I make exactly the same shape each time when I’m flattening more than one pipe – I use guides at each end of the pipe. My guides are simply two equal stacks of kitchen items built up to the intended height of the narrow cross section of my oval.

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Before I place the pipe in the pre-heated oven I make sure that my guides are in position and that I have my plank handy. The non-slip mat helps keep the hot pipe in position while I work on it. Once the pipe comes out of the oven you have to work quickly. Since the pipe is now hot and soft you also have to handle it very carefully – you don’t want to dent it accidentally.

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You place the hot pipe between the guides and then you immediately press down with the plank until the plank rests on the guides. You keep it down in that position for a minute or two until the pipe has cooled down a bit. I like to do this wearing heavy duty rubber gloves. The gloves offer a fair amount of heat protection while being nicely non-slip.

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After you have waited for the pipe to cool down a bit and have removed the plank, the pipe has been flattened and is now only as tall as the guides.

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If the re-shaping was successful your previously round cylinder should now be evenly oval.

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If you managed to mess it up somehow and you’re unhappy with the shape there’s no need to panic. If you didn’t overheat the pipe and you didn’t push down more than to half the original cross section, the pipe will retract back to its original round shape if you put it back in the hot oven. And once it’s been in the heat for 15 min you can try again.

 

For standard size round PVC pipes you get end caps that can be used to seal off the bottom of the pipe. For custom shaped oval pipes you don’t get ready made end caps. So, this is how I seal my oval pipes.

 

One plastic disk (cut from an ice cream container) to fit over the end of the pipe. One corrugated plastic disk to fit inside the pipe. The purpose of the smaller disk of corrugated plastic is to provide a few millimetres of space at the bottom end of the pipe. Once the disk has been removed and it’s time to push out the soap, I can stand the pipe upright and push straight down on the soap (the pipe will be wet with condensation moisture and typically slippery with soap so I prefer not to hold it any more than necessary) with just a bit of space for the soap to move. All I need is to get the soap to move a couple of millimetres and after that it slides out.

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The corrugated plastic disk goes inside the pipe and the larger plastic disk is sealed onto the pipe with Presstick aka Blue Tack. If applied carefully the Presstick provides a watertight seal. It’s easy to remove from the pipe, leaves no sticky residue and can be reused.

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But, I don’t trust Presstick on its own and so I also fasten a plastic bag with a thick, strong elastic band over the base of the pipe. Twice.

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Can’t really be too careful when sealing the base of a PVC pipe. If you’ve ever done the involuntary ’bag-pipe swirl’ (multicoloured soap from your pipe leaks into the bag that you’ve been prudent enough to stand it in) you know this 🙂

Once the soap is in the pipe it’s important that the pipe stands upright until it has cooled down completely. Why? Because heat travels upward and because soap expands as it gets hot and contracts when it cools down. If the opening of the mould is facing straight up the heat has a chance of escaping through the opening and the soap has some space to expand and contract. If the pipe is kept horizontal and the opening faces sideways the heat can’t escape through the opening. The hot, soft, expanding soap will build up pressure against the inside of the pipe and as the hardening soap contracts it will pull away from the wall of the pipe creating a dent in the soap and a vacuum in the space between the soap and the inside wall. This vacuum becomes a very effective airlock that sucks the soap to the inside of the pipe making it a real pain to unmould the soap. Keeping pipes upright and letting them cool down slowly is a good way to minimize this type of airlock.

Here my oval pipe with soap inside has cooled down completely and then spent a good 6h in the freezer. Freezing makes the fresh soap hard and less prone to damage in the unmoulding process. As the pipe warms up, condensation moisture forms between the pipe and the soap and helps the soap slip out of the pipe. (Pleased to see that nothing leaked through my Presstick seal.)

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Frozen top of the soap

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A few millimetres of space at the base of the mould once the corrugated plastic disk has been removed.

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A gentle tap with a rubber mallet on the side of the pipe and the soap slides out. I used to line these moulds until one day I forgot to do it and discovered that unmoulding was easier when the pipe wasn’t lined. I also find that unmoulding from oval pipes tends to be easier than from round cylinders. This might be because a flattened surface ‘gives’ more than a sector of a circle when tapped with a mallet.

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When the soap has thawed and the condensation moisture has dried it’s time to cut the soap.

_DSC0752Tuscan Violet freshly cut. The colour is a fair bit darker when the soap isn’t frozen anymore.

Some oval soaps made in my durable and very inexpensive DIY oval soap moulds. So simple – and very nice!

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Tuscan Violet handcrafted Soap by Auntie Clara's
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100 Responses

  1. Veronika

    such a genius idea! I wonder if the pipe’s bad stuff might leak into the poured soap, what do you think?
    Clara, I recently sent you 2 e-mails about the order but didn’t hear from you – did you see them? Just wondering…

    • Clara

      I don’t think there is any risk of anything harmful ‘leaking’ into soap from PVC. PVC does not react with NaOH or with the oils used and to emit harmful fumes PVC needs a higher temperature than your gelling soap will reach. I have not received either emails or an order. Please email me on auntieclaras@gmail.com.

  2. Janelle Peck

    This is fabulous! Thank you so much for sharing this! May I ask how you insulate your soap when using these molds?
    Your soap is so beautiful. My order arrived safely, and my husband immediately unwrapped an aviator bar and used it that same night. He is absolutely in love! I bought multiple bars so he could give them to his flight instructor, but I don’t think he wants to share!

    • Clara

      Thank you! I’ve learnt the hard way to make sure that these moulds are well supported while they are standing upright. They may seem pretty sturdy standing upright while they are empty, but the point of gravity shifts upward as they get filled with soap and then they easily topple over. Hence I stand the mould, or a couple of moulds in a sturdy bucket and fill the space between the side of the bucket and the mould with newspaper. The newspaper acts as insulation for the lower part of the mould and then I throw an assortment of old towels over the top part of the mould. In winter, when our floors are very cold, I stand the bucket on some folded towels.
      So glad the aviator is enjoying the Aviator soap! <3

  3. Helga Baumann

    A great tutorial! Thank you for sharing it! You could fill many a bookpage with your wonderful stories!
    Wonder when you will land in the “Oval Office” with your beautiful oval Soaps !? 🙂

    • Clara

      Thanks! I might have to land my soaps in the Land of the Oval Office first, before proceeding to the office itself.. 😉

  4. Laurie Coultrip

    Goodness. You have done it again. You are a treasure trove of lively, yet calm and lovely inspiration. My daughter, who cares only nominally for soap, but LOVES photography , pores over your site, imagining aloud your lighting and apertures …your backdrops …sigh. she wants to live where you do. So do I
    We think of you as the Ingrid Bergman of soap art !!
    Laurie ( st Louis < MO )

    • Clara

      Laurie, I believe you are the first person ever to have mentioned Ingrid Bergman and myself in the same sentence. I’m honoured! <3

  5. June

    Oh, my goodness! I tried it and it actually worked in just a few minutes in my oven! My oval isn’t perfect but close enough. I’m like you- there is something just, well, pretty about an oval bar. The mold I had been using was okay but a bit too small. Now there are so many choices to make with this technique. Thank you, again, for sharing your knowledge and the inspiration to create not just utilitarian soap but works of art. I’m trying to find plastic mats and tablecloths locally to try your lace mold techniques. I’m having a devil of a time finding anything locally so I guess I will have to resort to online buying. I found a tutorial to make a mold using kitchen ingredients and I’m going to give it a try and see if it holds up when soap is poured into it. If it works it will be so so much cheaper than silicone. Please keep sharing your beautiful creations and your DIY spirit- we all need inspiration! You rock!

    • Clara

      Thanks June! So glad it worked well for you! You are right in that silicone is quite pricey. On the other hand it’s also very durable and will give you a lot more use than many other materials.

      • Donna Brown

        Hi! I’m new to the site and wanted to put my 2 cents in. My silicone molds worked amazingly well the last time I made soap but when I brought them out this year, they were brittle and basically crumbled away. Bummer.

        • Clara

          I’m sorry about your moulds. There are many different types of rubber and silicone rubber and soap will need a type that can stand high pH. The MoldMax 20 or 30 silicone that I usually use to make moulds does not react with lye or raw soap and stays as flexible as ever year after year.

  6. June

    One more thing- my oven was set at 300 F and it only took a few minutes to soften and I used a thick-walled PVC. I didn’t notice any fumes at all. I don’t know the name of the pipe but the writing on it was black- got it at Lowes. Hope this helps someone.

    • Clara

      Thanks for sharing, I’m sure it can help someone. 300F is about 150C so a little warmer than my 120C. I like to keep mine at low heat for a bit longer to ensure that the PVC is equally hot – and soft – throughout. I’m no expert on melting PVC but I assume that it’s easier to get the pipe to flatten evenly if it has the same consistency throughout. The time it takes will of course also depend on thickness and type of PVC.

  7. Roberta

    Clara,

    There you go again. . .AMAZING! May I ask what size batch of soap fits your pipe (and how long is your pipe? Also, what did you use to cut your soap? It is so perfect.

    • Clara

      My pipes vary in length but the 42cm ones fit soap made with 1kg of oils and discounted water. I cut these with a wire cheese cutter.

    • Clara

      You have several options for a layered soap. You can alternate different colours as you pour the soap, you can use a smaller pipe inside the big one as a divider that you pull out once the soap has been poured, or you can make a cylindrical embed that you place in the pipe and pour soap around it.

  8. Madame Propre

    Oval soaps are indeed beautiful. I think I will try making those moulds! Your photos are excellent and this is such a good story YIU gave us again. Thank you Clara!

  9. Toni Larimore

    Wonder idea and quite simple, thank you for sharing! Another inspiring article and DIY. How do you remove the air from pouring the soap? Do you tap the sides rather than “pound” the mold? Or is your presstick and capping strong enough? Thanks again!

    • Clara

      If you make the Presstick seal carefully on clean, grease-free surfaces, it’s surprisingly strong. And once the plastic bag is secured with sturdy elastic bands, the whole thing can take quite a bit of banging. I stand my pipes supported in a bucket so I often just give the bucket a bit of a pounding against the floor while i hold on to the pipe.

  10. Nancy

    Oh my, thank you for taking time to share your creative step by step process. I tried this oval mold today, and it worked beautifully. It was fun, quick and already had these things on hand,. Can’t wait to pour my first batch. Many thanks for making the world a much richer place by sharing your experiencee and insights.

  11. Kevin Devine

    Great post as always Clara. While the tutorial is great I love your description of the start of your love affair; such evocative writing…you should do a book!

  12. Lea

    Dear Clara,

    A big fan of your from Korea!! Thank you so much for your sharing this precious idea and wish to try making this DIY oval shape of mold. One thing I wonder if you don’t need paper or anything inside of pipe in order for soap batch not to stick on the pipe? I am simply afraid that soap batch would stick to the pipe inside and does not come out of it.
    Thanks again, and will be waiting for your next post!! ^^//

    • Clara

      As I said, I used to line these moulds until one day I forgot to and found out that not lining is actually easier. Yes, the soap sticks to the inside of the pipe, but if you freeze it you can push the frozen soap out of the pipe.

  13. Soap Diaries

    Dear Clara,

    I am always amazed when the artist, so accomplished, will share with others and is willing to teach. Thank you for the continued inspiration,. May I ask, is your violet color custom? It’s a shade of Provence that I have been looking for, On another post, I wondered how you poured your soap into your wee hole in the egg? It looks tedious but I So wanted to try it and give to my 11 grandchildren!

    • Clara

      Thank you! The violet is my own blend of violet and blue ultramarine. To pour soap through a very small hole the batter needs to be at the very runny, i.e. at emulsion rather than trace. Also, using a jug or pitcher with a fine spout helps getting the soap where it’s supposed to go. Alternatively you could use a piping bag and nozzle.

  14. Judith Best

    this is a great tutorial! Might I ask what is the best way to impress a design on the cut oval bars? I am a beginner and am interested in only making soap for my family. Thanks!

    • Clara

      The best way to impress a design on soap is by using a soap stamp. Soap stamps are available online or you could make your own. On Auntie Clara’s Handcrafted Cosmetics Facebook page you will find a stamp making tutorial in one of the photo albums

  15. Robin Helscel

    You are just a genius!!!! You truly do inspire me and my soapmaking!!!!! Thank you for sharing all that you do!!!

    Robin 🙂

  16. Anne-Marie

    Oval shapes are so cute =) the green and blue colors are great for spring. This is an awesome tutorial. Am totally tweeting it. Thanks for your generosity in sharing it!

  17. Roberta

    Clara,

    I wrote previously with some questions about this beautiful soap. I hate to bother you again (and I have not seen another post on the same) but I am having trouble accessing the “right” kind of PVC pipe. Here in the states, I have gone to Home Depot and Lowe’s (hardware stores). The pipes they carried had only a 6mm wall; too thick. They asked me to ask you if there any markings on the outside of your pipe to designate it and also suggested that I go to furnace store and ask for PVC pipe that direct vents wood stoves etc. I’m surprised that I am having trouble. . .thought this part would be a “no-brainer.” Any more tips would be helpful.
    Thanks

    • Clara

      I’m not at all sure that 6mm would be too thick. Again I’m by no means an expert at melting PVC, but I’don’t see why 6mm PVC wouldn’t melt just as well as thinner PVC. You might have to adjust the time a little to accommodate for thicker material though.

  18. Adrienne

    Thanks so much for an enjoyable experience. I have just successfully made a small oval mould using your tutorial and I feel quite proud of myself. Now I can’t wait to use it. I think you are quite amazing and I get hours of pleasure from your Blog. THANK YOU for sharing with us. I have one question, I don’t belong to Facebook is there any other way to access the ‘Stamp Tutorial’ and the photo album? I would really love to see them.

    • Clara

      Glad you had success with the oval mould! The Facebook album with the stamp tutorial is public so anybody can see it whether you belong to Facebook or not. This is the link:

  19. robin mosenfelder

    unable to locate “presstick” or “blue stick” in USA ( via Amazon). could it be called something else or can you suggest a substitute? What is it commonly used for?

  20. Nicole

    Clara,
    Your soaps are very beautiful and inspiring and your stories and descriptions of Africa are lovely. I appreciate your sharing information. I am new to soap making and I am wondering how you cut the soap after removing from the mould? Do you have to trim or modify the surface to create such a perfect appearance?

    • Clara

      Many soapers plane their soaps for a smooth appearance. I bevel off sharp edges but i never plane my soaps. I find, though, that not cutting too early helps a lot in making a smooth cut surface. If you have any concerns about the soap still being slightly soft, it’s better to postpone cutting another 24h or so. In this respect patience is a virtue.

  21. michele

    Best soaping tip ever!!! Just finished baking and smooshing my mold. Sooooo happy with the results. I used 300 degree oven for 4 minutes. I have been looking everywhere for an oval loaf soap mold and no one sells it anywhere. I paid $8 for a piece of PVC, I cut it in half, and now I have two molds I really will use. Can’t wait to use it tomorrow! Thank you for this fabulous, simple, easy, and affordable solution to my six hour internet search!

  22. Gina

    I have just discovered your site. It is absolutely fabulous. Thank you for sharing so many wonderful pictures. I do have one question – the oval soap with the fish. How did you create a divider that gave you such a perfect wave of the two colours? I use dividers but never have done anything other than insert a smaller tube in the larger one and then pull it out.

    Simply lovely!

  23. Zenob

    Hi Clara,

    Really great tutorial. Have recently started making cold process soaps. Love the process and the soaps. Your soaps and the stamping look great. Thank you for sharing.

    You have replied to every single comment. That is quite commendable.

  24. Annik

    Thank you for your many tips !!

    I recently sent you an e-mail, did you get it?

    I just unmold my first oval soap, I’m very happy 🙂 🙂 🙂

    Thanks!

    Annik Belgium

  25. Soaper Sharon

    I am so thankful that I found your tutorial, as I too desired to make oval soap.
    My experience: I used 5mm thick pipe 18 inches long. I put them in a 250 degree F. oven for 10-15 minutes till soft. Formed them as you directed.
    I cut out silicone pieces from a loaf mold (that I no longer used because I did not like the tapered sides) to fit the bottom of each pipe, then duct-taped them securely to the bottom. I taped 4 molds together while standing to make them sturdy. Covered with towels.
    After 3-4 day, I put in freezer overnight. The next day I ripped off the bottoms and stood them on the counter for about 10 minutes. Condensation was forming on the outside. I only had a wooden mallet, so tapped (more like, banged!) the outside and some started slipping out. It was very difficult to pull out, so I taped 2 -1″ dowels together to make a sort of plunger or “pusher” to push soaps out while my husband pulled. I have to say this took quite a bit of muscle and was no easy task.
    Now, I’m wondering if lining or spraying would be easier….your thoughts?

    • Clara

      I don’t spray or line. I did line with various things including baking parchment and flexible cutting boards until I found that not lining was actually the easiest. A couple of things though:
      First the shape of the pipe. Unless you manage to press down evenly along the pipe you might get an oval pipe that’s flatter at the one end than the other. Even a very small difference will make the soap more difficult to unmould. Second, bunching the pipes together is probably not only a good idea. Yes, I agree that it will help keep the pipes upright as they support each other, but it can also cause the soap in each pipe to heat up differently on different sides of the pipe. The side closest to the other pipes is likely to get a lot warmer for longer than the side facing out. The soap on the warmer side will expand more from the heat and in turn contract more as it cools down which can lead to vacuum pockets forming between the pipe wall and the outside of the soap. Those vacuum pockets effectively suck the pipe to the soap making unmoulding harder (that’s where the banging comes in handy; it breaks the air lock). Next time you could try going over the pipes on all sides with a hairdryer or a heat gun immediately after taking the pipes from the freezer. The difference in temperature may help break the air lock.

  26. Nadeen

    Hello Clara! I am so pleased to find this tutorial. I wanted an oval mould for ages and was a bit hesitant to spend money on multiple silicone moulds. Plus – should I share this… I don’t know, but I am a bit addicted to cutting soap. I LOVE it. So an oval log mould will be making an appearance in my little soap arsenal. Although my soaps are not as lovely as yours – I have a long way to go before I am ever that accomplished…if ever at all.

    I’m definitely going to try this – I think it will be easy because your instructions and pictures are exceptionally well presented! Plus the size is perfect, since I will only be selling my soaps to the locals at my little French market. No need for industrial scale soap moulds.

    • Clara

      I hope it works well for you, just make sure that you put even pressure all along the pipe. And pipe isn’t expensive so it’s worth the try.

  27. Alliya

    Genius ab-so-lute-ly Genius!! I have been looking for an oval shaped column mold for years. I too love an oval shape (I insisted on an oval dining table). But the individual Val molds are too much trouble. Yes! I will be heading to the hardware today to get me PVC pipe for this project. One quick question do the fumes linger in the oven and btw is that a gas or electric oven. Yipes! My cooker is gas….

    • Clara

      My oven is electric and a lot of gas cookers have electric ovens. But I don’t think gas or electric really matters as long as you can keep a nice low temp. The fumes don’t linger; as long as you don’t accidentally get molten pvc on any oven surfaces it’s fine to just air out the oven properly after heating the pipe.

  28. Ada Stafford

    Do you only do CP in the PVC pipe? I ask because I do HP only in the PVC pipe. My problem is what I call heat tunnels. I am not really sure that’s the name for them but they look like worm holes in space. Most of my soaps get it and it can ruin up to about 4 inches of soap. I have tried molding molding at various temps. Not putting them in the freezer and going directly into a deep freezer. It doesn’t matter. My molds are 12 in tall. Do you think making them shorter (like 6 in) would make a difference. I was just wondering if you had ever heard of this happening. Thank you so much for your time.

    • Clara

      Technically your heat tunnels are actually ‘cooling tunnels’. When you put hp in a pvc pipe the soap is hot when the pillar of soap is built up inside the pipe. Hot soap has a larger volume than cool soap, primarily due to heat expansion of water in the soap/soap batter. As the soap in the pipe cools down it contracts. Depending on how hot it was when placed in the pipe and how much water it contains it contracts more or less. For the soap to keep its shape as it contracts it needs to gradually replace the decreasing volume with air. Because the pipe is tall and narrow the soap cooling down in the lower part has no access to air and creates vacuum instead. The empty space that that vacuum creates sometimes shows up as ‘dents’in the side of the soap, but if the soap was very hot when placed in the pipe and contracted a lot you might get the kind or wormholes that you describe inside the soap.
      The best way to avoid ‘cooling tunnels’ is to keep pouring temps as low as possible (tricky when doing hp) and water as low as possible (also tricky when doing hp).

  29. Debra Tyler

    I love the way you share your experiences with soap experimentation with everyone. I have been experimenting with ovals myself, but with silicone moulds. I would like some ovals to be a bit larger, so I think I will try your technique. I am intrigued by how you wrap your oval soap, Do you have a template which guides you and do you wrap by hand, it looks so neat and professional on the sides (no pleats until the top of the soap). Would you mind perhaps sharing a tutorial on how you wrap your oval soap?

    • Clara

      It’s a simple method. I wrap a rectangular strip of wrapping paper around the circumference. Then I just stand it on the crumpled bottom while I mitre the top, turn it upside down, straighten out the crumpled bits and mitre the bottom side. A top label and a bottom label keeps it all in place.

  30. Judyta

    Hi! Great tutorial, thanx for sharing it 🙂 I can’t wait to make oval soap! Just got one question, can I make soap containing milk in it or it will get to hot in the pipe?

    • Clara

      Soap with milk gets hot in whatever mould and in a column mould like this the heat doesn’t have much of an escape route. If you use column moulds for milk soap I suggest you do a very steep liquid discount. With less liquid you’ll have less expansion from heat and less risk of volcanoes.

        • Clara

          That depends on what goes in the soap. You can go as low as 1:1 liquid:lye, but then you’ll have to be prepared for acceleration. If you are using accelerating additives you might have trouble getting the soap in the mould before it gets too thick.

  31. lois

    hi, these soaps are oh so pretty!!! Though I have a question regarding your soap stamp: Is the Chinese stamp supposed to be ” auntie ” or soap? I’m Taiwanese and I didn’t know 胰means soap. And I look up online dictionary, it said it means a.pancreas b. Soap But in modern language I don’t think people know this. Might have been an ancient literal usage or Simplified Chinese usage. Or do you mean auntie? Coz there are two word for aunt in Chinese. 姑 means paternal auntie, and 姨 means maternal aunt. I hope I don’t sound rude or impolite by saying all that, just need a clarification. 😉

    • Clara

      I think it just means ‘pancreas’ – and I’m OK with that 🙂 It came about because of some video which apparently erroneously said that the character could mean both ‘pancreas’ and ‘soap’. I quite liked the idea of that duality and decided to go with it, but it seems that some find it offensive that I write ‘pancreas’ on my soap. Caving in to social preassure I have therefore since made a different stamp with a character that actually says ‘soap’ – or so I think 🙂 Thanks for the characters for ‘paternal auntie’ and ‘maternal aunt’. One day I might make stamps with those and if I do you must know that I got the idea from you 🙂

  32. Pauline

    Awesome tutorial, dovu have something that shows how you pore two different colours into pipe please?

    • Clara

      I don’t have any pictures but you basically just insert a flexible cutting mat rolled into an s-shape into the pipe and pour the soap in the different ‘compartments’. Remember to remove the cutting mat once you’re done pouring.

  33. Cynthia

    Brilliant idea! Thank you so much for sharing. I will definitely be trying this in the future.

  34. Crystal

    I have no idea how you got the soap out of the mold because mine is good and stuck Everything else worked great. I think next time I will line it with something, lol.

    • Clara

      When you pour into a column mould like this it’s wise to leave about a cm or two of empty space at the top. Once the soap is fully saponified and the pipe feels cool to the touch you place it in the freezer for a few hours. Once well frozen you take it out and give the pipe a good few knocks from all sides with a mallet. Leave for a few minutes for condensation to build up then drop the pipe on ‘it’s head’. Gravity will loosen any airlock inside the pipe and the soap will slide out. This, of course, provided that your oval pipe was evenly shaped and isn’t flatter at one end than the other.

  35. Anita

    Hello Mrs..Auntie Clara. I really love your soaps! Very classy and elegant. May I ask where do you get your soap stamps?

    • Clara

      Hello Anita. My name stamp is from a local signage company and most of my other stamps I have made according to the tutorial which you can find in the photo albums on my facebook page.

  36. Tessa van Niekerk

    Net n Suid-Afrikaner sal die geheime grap agter die “Nkandla Shower Soap” raaksien en waardeer! Baie dankie vir die raad! Gaan ook van nou af PVC pyp probeer.

    • Clara

      Strictly speaking I’m a Finn and not a South African. You must know though, that it’s a special kind of insanity when even the foreigners are in the loop 🙂 Hope the PVC pipe works out well!

  37. Sharon

    So very excited to try this. I’ve admired your soaps (especially the oval ones) for so long. I never thought to see if you had a tutorial. And an amazing one at that. I loved the beginning the most I think. Thank you for sharing.

  38. Terri

    Our home is on propane. To save money on propane and to not have pilots going during the summer We disconnect the oven and use electric induction cook tops and a slow cooker. In my studio I use a large slow cooker for my soap making. Do you think heated water in my slow cooker would soften the pvc pipe enough to make the oval shape?

    Thank-you.

    • Clara

      It might; you’ll know if you try. I keep my oven set at higher than 100C, but the PVC may well be soft enough to shape at slightly lower temp than 100C.

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