How to make a new bar of soap from leftover soap

How to make a new bar of soap from leftover soap
How to make a new bar of soap from leftover soap

If you want to dive into the world of soap making, but are afraid of handling soda, you might consider making your soap using leftover old soaps. This is a great way to learn the basics of how to make this product and to experiment with different substances, for example oatmeal or essential oils. You can also use this method to reuse homemade soaps that you missed. This process keeps you from wasting less successful batches of soap.


Part 1 of 3: prepare the base

Step 1. Pick out some soaps

You can use whatever type of soap you want, but you will get best results with fragrance-free and natural products, such as pure Castile soap. This will give you more customization options later. You should try to get at least 350g of soap.

  • When finished, the repackaged soap will have a grainy texture. It will not be as smooth as normal soap.
  • If you are using leftover more than one soap, you must try to use the same scent or you will end up with a product that does not smell very good.
  • You can use different colors, but remember that they might not always blend together well to produce a new color. Sometimes there might be stains.

Step 2. Grate or cut the soap

The best way to do this would be to do this with a grater, but you can also mince the soap with a knife. The smaller the pieces, the easier the soap will melt.

Step 3. Put it in a double boiler

Fill a saucepan with 2 to 5 cm of water. Place a heat-resistant container in it. Make sure that the bottom of the container does not touch the surface of the water. Pour the grated soap into it.

  • If you have a pot, you can use it.
  • You can also melt the soap directly in a saucepan without a container, but you need to make sure that it is small enough that the soap does not stick.

Step 4. Pour a little water into the soap

You will need 250 ml of water for 350 g of soap. This will help you soften it. Avoid putting too much liquid or the product will not dry well.

  • If you want to make a more special product, consider putting tea or milk in it instead. You can also try goat's milk or buttermilk.
  • If you are using freshly made, cold pressed soap, you won't need as much liquid, if at all.

Step 5. Heat the soap

Stir it every five minutes. Heat it over medium heat and let the water boil. Stir about every five minutes using a wooden spoon or rubber spatula. Make sure you scrape the bottom and edges of the container well.

  • If you are using a pot, cover it with a lid and let heat over high heat. You need to open the lid every now and then and stir the soap to make sure it doesn't burn.
  • If you heat it in a saucepan, leave it on low heat.

Step 6. Continue heating and stirring

Continue until it softens. Refurbished soap will never melt like fresh soap. Instead, it will take on a grainy texture, much like oatmeal or mashed potatoes. Be patient. It can take between one and two hours.

  • At a certain point, the soap will no longer change its texture. Once you are there, if the soap still looks the same, it will not continue to melt. You are ready for the next step.
  • If it starts to hang, lower the heat and add a little cold water.

Part 2 of 3: Add additional products

Step 1. Let cool to 60-70 ° C

You don't need to add the extra products shown in this section if you don't want them, but they could add extra charm to your soaps. You can also choose to add some and not others. Pick one or two (or even three) that interest you the most.

Step 2. Give it more perfume

You should put about 15 ml of fragrance or essential oil for 350 g of soap. If it's already scented, you should skip this step or use a similar scent. For example, if the soap smells like lavender, you can add an extra small drop of lavender essential oil.

  • Do not use as much essential oil as there is fragrance, as essential oils are generally stronger.
  • Do not use candle scent. It should not be applied to the skin.
  • You can also give it more flavor by using spices. They will also color your soap. Consider using between 1 and 2 tsp. to s., for example ground cinnamon.

Step 3. Incorporate nourishing oils

If you want a luxury product, you can add a few drops of nourishing oil like vitamin E, jojoba oil, almond oil, etc. Anything you put on your skin will be great in your soap. Do not be too heavy a hand anyway, too much oil could affect the finish of the product!

You can also put honey in it. It will make your soap more nourishing and fragrant while giving it a golden color. Consider using between 100 and 200g of honey

Step 4. Add a few drops of soap colorant

Since the colorant is translucent, this option is only recommended for white soaps. Buy it online or at a fine arts supply store. Add between one and two drops and stir well. Continue to stir until the color is even. If the color is not deep enough for your taste, you can add an extra drop.

  • The soap dye is very strong. Add only a drop or two at a time until you get the color you want.
  • You must use soap dye. Do not put candle dye in it, as it is not good for the skin. The food coloring isn't going to work either.
  • You can add coloring to revive an existing color. For example, you can make soap blue deeper by adding a little blue dye.

Step 5. Add texture with herbs or exfoliators

It is a good solution for people with dull or dry skin. The exfoliators will scratch the surface of the skin and make it softer. You can, for example, put sea salt, oatmeal or dried lavender buds in it. Here are the recommended quantities for 350 g of soap.

  • About 100g of exfoliators like oatmeal, almond flour, coffee grounds, etc.
  • 50 g of plants with low volatility oils such as chamomile, marigold and lavender. You can choose dry or fresh varieties.
  • Between 1 and 2 tsp. to s. plants with very volatile oils such as rosemary. They can be fresh or dried.

Part 3 of 3: mold the soap

Step 1. Prepare the mold

Buy a plastic mold for the soap. If the mold is standard and you want to make more elaborate soap, you can add a rubber stencil to the bottom of the mold. If you wish, you can brush the inside with a thin layer of cooking oil. Alternatively, you can also use petroleum jelly instead.

  • You can purchase molds and stencils online or at art supply stores.
  • Alternatively, you can even use an ice cube tray or cookie mold.

Step 2. Pour the soap into the mold

Since the soap is too thick, it will not be possible to run it into the mold. Instead, use a wooden spoon or rubber spatula to pour the soap into the mold. Smooth it out by pressing it into the mold with the spoon or spatula.

Step 3. Drop the mold

Hold it 15 to 30 cm above the worktop and let it fall. This will install the soap in the mold and remove air bubbles. You may have to do this several times.

Step 4. Let dry for a day or two before unmolding

Once it's dry, you can unmold it. If you are using long, rectangular molds, you can cut your soap into thick slices 3 cm wide.

If you are in a hurry, you can put it in the fridge for an hour or two before unmolding it

Step 5. Let it dry longer if necessary

Depending on the type of soap you used, your batch may still be a little soft. If so, you can put it on a rack and let it air dry for two to four weeks. If you are using store-bought soap it is not necessary to do so, but if you have used fresh soap it probably will.

Some types of reconditioned soaps (usually those made from store bought soaps) only need to dry for two days


  • You can also use leftover soap by opening a bath sponge and putting the pieces in it. When it's wet, it will lather up and squeeze out any leftover soap you've put in there and can be used to wash yourself off.
  • You can also let them soak in water until they become softer. Then squeeze them between your hands so that they form a single block. Let it dry a bit until it hardens and you have a new bar of soap.
  • You can also reuse leftover soap when you are about to start a new bar, just wet it and stick the soap scraps on it. Let it dry until the next shower. The pieces will be glued to each other.
  • Refurbished soap will still have a grainy texture. It will never be smooth as if it had just been cold, hot or melted pressed.
  • Leave a window open or turn on a fan, especially if the soap is scented.
  • Some stores sell "refurbished bases". You can melt them to a smoother consistency, much like cake batter.

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