Cold Process Soap Making Method (CP)
Posted March 13, 2007on:
Preparing To Mix Soap
My personal preference is to work at medium to low starting temperatures, and to measure by weight all ingredients, including water, and only excluding the essential oils, which I measure in milliliters. Also, I use a stick blender, which cuts down enormously on stirring times. In detail, here is what I suggest you do:
- After choosing the recipe and calculating the amounts of the ingredients (oils/fats, caustic soda, water, fillers and fragrance), prepare your working space – i.e., put away things that might become contaminated and cover the surface with a layer of old newspaper.
- Collect all the equipment, the ingredients, and the containers and tools you will need for this batch of soap.
- Find a few old towels, or a blanket, or some heavy rags for insulating the moulds. If you’re planning to fill the moulds to the brim, you’ll also need a roll of baking paper (or plastic film, or some heavy duty plastic).
- Prepare the lye solution: measure the required amount of cold water in a heat resistant container. I use a heavy plastic (HDPE) jug, which has a fitting lid.
- Place this container in the sink, and fill the sink with enough water to reach the level of the water in your container or more. Just make sure the container doesn’t float too much (it will get heavier when you add the caustic, anyway).
- Wear your protective clothing (gloves mask etc.)
- Measure the required amount of caustic soda in a clean, dry container.
- Add the caustic soda to the water a little bit at a time, but not too slowly, and stirring continually with a long handled tool (I use a paint stirrer).
- Avoid breathing in the fumes. If you can, I suggest you mix your lye solution outside (wind at your back, if any ;-). Make sure there is a water tap close by, in case of accidents.
- Cover the container with the lye solution.
- Measure your oils or fats directly in your soap pot. I start with the solid oils/butters to avoid splashes.
- Place the soap pot on medium heat.
- While the oils/fats are melting and the lye is cooling down, assemble measure and organize your extra ingredients.
- Line the mould (if you’re using a log, slab or divider mold), or otherwise prepare your moulds (some types of plastic tray molds require greasing)
- Determine where to place the moulds, and place a towel or thick layer of newspaper under the moulds. Remember you will not move the moulds for the first 12 to 24 hours – so choose a spot where the soap can be left undisturbed!
- When the solid oils/fats are melted, turn the heat off under the soap pot and measure the temperature.
- As I mentioned, I like working at medium to low starting temperatures. I suggest you start getting ready to mix your soap when the oils are around 45º C / 110º F.
- If the fats/oils are warmer than this, just go and do something else while you wait – or you can place the soap pot in a sinkfull of cold water to speed up the process.
- When the oils are at the desired temperature, check the temperature of the lye solution. Typically, this will be lower than the temperature of the oils – which is perfect!
- If the lye solution is still much warmer than the oils, I suggest you try and cool it down by adding more cold water to the sink.
When the oils are around 45º C / 110º F and the lye solution has reached the same (or cooler) temperature, you can start getting ready for mixing the soap.
- Place the soap pot on a flat, safe surface (the stove is not safe enough, in my opinion).
- Add the lye solution to the oils in a steady stream, but not too fast, while stirring continuously with your long handled tool.
- Stir with slow, even movements to avoid splashes.
- The mixture becomes opaque and starts taking a lighter color.
- Once all the lye solution has been added keep stirring for a couple of minutes.
- Get your stick blender ready (you can leave the soap mixture unattended while you do this).
- Place the stick blender in the middle of the pot, resting it on the bottom (or as close to the bottom as you can if you’re making a large batch). Make sure the level of the soap mixture is at least a couple of inches lower than the motor of your stick blender, and the blades of the stick blender are covered by at least 3 inches/7 cm of soap mixture!
- Start the stick blender and operate it in short bursts.
- As the mixture gets lighter in color, and starts assuming a creamy appearance, you can operate the stick blender with no interruptions for longer periods.
- To avoid overheating the motor, turn the stick blender off and use it as a manual stirrer periodically.
- Within 3 to 10 minutes (depending on the type of fats/oils, and other variables), the soap mixture will be smooth and glossy, with similar consistency and “feel” to thin custard.
- This is the beginning of “trace”, a.k.a. thin trace. This is an important stepping stone for adding some particular ingredients or carrying out some special operations (for instance, dividing the batch if you’re working on a swirled soap).
- Unless you have some special reason for stopping at this point (see above, or refer to your recipe instructions), keep stirring until the mixture reaches full trace. When using a stick blender, this might take anything between 20 seconds and a few minutes after thin trace.
- You’ll know you have reached full trace when a little bit of the mixture, dribbled from the stick blender, will leave a “trace” before sinking.
- You can now add the fragrance or essential oils and the other ingredients you have reserved for adding at trace.
- For this, you can set the stick blender aside and go back to your long handled spoon. Make sure you blend the oils (or whatever) thoroughly, and don’t forget to scrape down the sides of the pot.
- Pour the soap into the mould(s). It is best to do this slowly (see the picture above? the pot was very full and very heavy, and I thought I could get rid of the weight quickly…. Luckily, the “soap splash” remained inside the mould!)
- If you’re using individual moulds, you might find it easier to ladle out the soap mixture, at least in the beginning.
- Pour out as much of the soap mixture as you can, and scrape down the pot properly.
- Cover the soap with the towels (or blankets, or rags). Remember to place a piece of baking (greaseproof) paper on top, if the mold(s) are filled to the brim.
- Arrange the towels/rags so that the entire mold is covered – top and sides.
- Leave the soap undisturbed for 12 to 24 hours. Insulating the soap helps speeding up the saponification process (the chemical reaction), and properly mixed and insulated soap is usually caustic-free after as little as 24 hours.
Gel Phase and Unmolding
A good way to understand if your soap is coming out properly is to have a quick peek after 2 to 4 hours after pouring. By this time, properly mixed and insulated soap will have reached gel phase, and will look translucent and *much* darker then when you poured it. This is perfectly normal, and really, I think this is the only way to be sure that what you’ve done is going to be soap…. soon! 🙂Since there’s no precise step to follow at this stage, I will simply give you a list of notes and comments:
- Try and keep the soap in gel state as long as possible (that is, do not move the moulds or remove the insulation layer).
- After 12 to 24 hours, the soap should be ready to unmold.
- Properly made and insulated soap is opaque and solid, and should not be covered by any “soap dust”.
- Soap dust is a white powder that may appear on the surface(s) of the soap exposed to air. Chemically speaking, this may or may not be sodium carbonate, a mild alkaline salt that forms when the still caustic soap mixture reacts with the air surrounding the soap, and is totally innocuous. Another theory is that this white powder is simply “dry soap”. Discussions abound on this subject, and my personal conclusion is that it’s not worth worrying (too much) about it…. 🙂
- Unmold the soap and leave to cure at room temperature.
- Arrange the soap on your chosen “cooling racks” (for instance, clean cardboard trays, such as those used by greengrocers for exotic fruit) so that air can circulate around each soap.
- If you live in a very humid climate, it might be safer to cure the soap in air tight plastic containers. Experiences and opinions on this subject are not unanimous – my personal experience is that a humid room is a lot more “dangerous” than an air tight plastic box, and I know of soapers (in tropical Australia) who simply avoid making soap during the monsoon season.
- Curing is basically needed to get rid of the excess water, as well as an extra precaution to make sure no free alkalis are present.
- Well cured soap has a richer lather and lasts much longer than fresh soap.
- If you have precise pH strips, you can test the alkalinity of your soap. At the end of the saponification process, natural soap will read between 9.0 and 10.5.
- In my experience, the pH of properly prepared, mixed and insulated soap does not change over time.
- There are more empirical ways for testing the alkalinity of soap. The most popular is called “tongue test”, and I personally like the way “Hersh” (James Hershberger).
- A simpler and less painful method is to wash your hands with the soap. If it burns, or if it leaves you with a “boiled skin” feeling (similar to what happens after soaking in a hot bath for a long time), or if the lather feels slimy and rinses off with difficulty, then the soap is still caustic.
- This might change over time. So before deciding your soap is too caustic, leave it to cure for another few days.
- If the burning/slimy/boiled skin sensations are still present after one week from unmolding, then there is too much free caustic soda in the soap. Double check your recipe and notes: did you leave one of the base oils out? Did you check the accuracy of your scales? Did you double check the initial calculations using a reliable SAP calculator?
- In my experience, soap that still feels caustic after two weeks from unmolding is most likely a “lye heavy” batch.
- The fact your soap is lye heavy doesn’t mean you must throw it in the bin. On the contrary! Soap can always be rescued – for instance, you can rebatch the soap adding some extra oils, or you can make some laundry gel.
Source: Aqua Sapone