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Gather and measure the ingredients shown above or from one of my other cold process recipes. You will need to measure your ingredients carefully, Do Not try to guess or use cup sizes as when you make soap it needs the correct mixture to complete the saponification process. Use either grams or ounces, do not mix the two. I prefer grams as I find it much more accurate if you need to convert ounces into grams for any reason simply multiply by 28.35. More information on measuring, easy conversion and other cosmetic tips can be found here.Prepare a mold. If you don't have a specific soap mold, then any good size container will do. Sturdy plastic containers that still have enough give to ease the soap out make the best containers because you don't have to line them. Recently I've been using silicon molds as it's so much easier to remove the soap. A quick grease round with a little solid oil from the recipe and they're good to go. Glass, wood, ceramic or cardboard all lined with freezer/butcher paper will also make suitable molds. Avoid using any metal molds unless you can be sure they are stainless steel.
Now its time to mix the lye with water, and as I already mentioned above, this is a chemical reaction so we need to take some precautions.Make sure you are making the soap in a well-ventilated area. Put on your gloves and eye protection, your mask, apron, and long rubber gloves. Pour the mineral water into a large glass/sturdy plastic jug or plastic bucket. Now, slowly, pour the lye into the water, using a plastic spatula to stir until dissolved. The water will start to heat when it reacts with the lye (caustic soda/sodium hydroxide), it will need to cool until it reaches the required temperature (see specific recipe).
In a large stainless steel or enamel pan, gently melt any oils or waxes over a low heat. (this does not include essential oils or fragrance oils). Use two candy thermometers place one in the caustic soda mix and one in the oil mix.Update;I now use an infrared thermometer gun, it's much easier.When both mixtures reach an equal temperature begin to pour the mixture and stir the lye solution into the oil, DO THIS SLOWLY, and remember that you should always add lye to other materials, not the other way around, pouring a liquid into lye crystals can cause it to splash and can burn your skin.I recommend combining at a balanced temperature of between 120F and 140F (49C-60C).Caution: Be very careful handling and mixing the lye. It is extremely caustic and can burn if it gets and stays on the skin. If at any point you spill or splash lye or caustic batter onto your skin, wash it off with lots of water right away. You can also use some kind of vinegar or lemon juice to calm the burning and wash away the lye, then rinse thoroughly with water. Remember that lye is alkaline, not an acid, and so a gentle acid should help to neutralize the lye. If this doesn't help, seek advice from a medical professional as soon as possible.
Using a stick blender begin carefully stirring your mixture for several minutes, slowly at first without switching the blender on.
Reaching The 'Trace' Stage: Then give your mixture a few short 3 second bursts, stirring between each burst until the mixture thickens slightly and looks a little like thick custard. This is called "trace" and it's a sign that your diy soap is turning out well. By dipping your spatula or spoon into the mixture and dribbling a small amount back into the mix. It should leave a light "trace" behind (like a small mound of batter that takes a few seconds to blend back within the mixture.) This is when you know you've reached the "trace" stage.Or by hand which will take a little longer, maybe up to an hour but with consistent slow even stirring with a hand whisk you will eventually reach the trace stage.And now is usually the time to add any extras like flowers, fragrance, essential oils, colors or textures into your recipe. But check the individual recipe to be sure. There are so many things that you can add, check out some of these interesting soap making ingredients and textures.
Pour your soap into the mold and smooth out using a spatula.
I find it's helpful to cover the top of your soap with a purpose cut peice of cardboard.
Wrap an old towel around the whole thing to keep the heat in.
Allow your diy soap to set for 24 hours in a warm place until the soap has hardened. Don't be too alarmed if you take a quick peek at your soap and it looks translucent, this is called the gel stage and is perfectly natural. When it has hardened (usually around 24 hrs), remove from the mold and allow it to air for a few hours. When removing from the mold, remember that the lye is still active, and can still cause skin irritation - always wear gloves.
As a general rule, it should be about the consistency of hard cheese before you cut it. The soap will still be caustic at this point so I would recommend still handling it with gloves for the first 48 hours.
Cut it into bars, for this you can simply cut by hand for a more rugged look. Or use your soap cutting box for something more symmetrical.
The final step is to cover/line a cooling rack, tray or box with a cloth and stand the bars upright without touching each other so the air can circulate. Store them in a dry ventilated place turning them each day in the first week and then every other day thereafter for 4 weeks. This time continues the curing process ensuring that all of the lye has been neutralized and water evaporated. During this time your soap may develop a fine dust layer, this is soda ash and can be scraped off before use.
All of the homemade soap recipes on Savvyhomemade allow 5% superfatting. This ensures correct saponification (the reaction that creates soap) making sure there is zero free caustic alkali remaining and a good ph balance is achieved.
As long as you have measured your ingredients correctly you have nothing to worry about. To be sure always test soap using a ph strip to make sure it is somewhere between 7-10.
To get a good idea of the size of mold needed add together the oils and water in the recipe and then fill a mold with that amount of water.
The best way to line your mold when using the freezer/butcher paper is to cut two strips, one to go across the width of your box and the other going across the length. Leave enough on the paper to fold over the edges and secure with tape.
If your soap does not harden or just hasn't turned out quite as well as you expected it to, or maybe you forgot to add something. Then you may be able to rebatch it by melting it down and adding any missing, or miss calculated ingredients.
If your batch is too lye heavy, making it very brittle and crumbly or if your lye and oils have separated (you will notice a layer of liquid on the top or underneath the soap) I would encourage you to discard it.