Please note: Since we no longer offer cold process soap supplies, we offer this free information to you, but cannot offer any type of technical assistance pertaining to any form of cold or hot process soap making. Thank you!
The hot process method of soapmaking is carried out the same way as the cold-processing method, but in hot-processing the traced soap is further cooked in a double boiler until it is neutral. Neutrality has to be achieved in order to achieve transparent soap products.
Equipment you will need:
Stainless Steel Measuring/stirring spoons
5-gallon Canning Pot-for double boiler
Pot for melting oils and fats (small enough to fit inside canning pot)
Large Stainless Steel Bowls
Heavy Duty Rubber or Silicone Spatulas
Safety Equipment- goggles, rubber gloves, apron.
Digital Scale that measures grams and ounces
Lye (potassium hydroxide)
Additives (vitamin E for preserving)
Measure all ingredients exactly and keep notes! Failures will later be seen as your successes!
Fill a double boiler with 3 inches of water and put it on medium heat. You will be placing your soap pot inside of this to create a double boiler . For now, just place it on medium heat, covered, on the back burner.
Get your fats and oils ready- Weigh out all of your fats and oils, and place them in your soap pot over medium heat . You will melt your fats first, and then your soft oils. Heat until the oils reach 160 degrees. Turn the heat to low and maintain the temperature.
Prepare your lye solution- Make sure you wear goggles, rubber gloves, and an apron. Do not breathe the lye solution! Measure out the water portion of the solution and pour it into a canning jar. Now weigh out your lye (potassium hydroxide). Add the lye to the water and stir until it is thoroughly dissolved. DO NOT ADD THE WATER TO THE LYE! Keep vinegar on hand if you happen to get the lye solution on your skin! Allow the lye solution to cool to 140 degrees.
Add the lye solution to the oils (which should be 160 degrees). This should be done in a slow steady stream, and should be stirred constantly. Stir this mixture with a stick blender. Do not stop mixing when you notice thickening; you will want this mixture to become like paste.
Now you will enter the hot process portion of soapmaking- Place the soap pot into the double boiler you got ready. Cook the mixture. After about 10 minutes, remove the soap pot and look to see if there is any lye separation (caused by not stirring long enough). If it is showing separation, stir, then place soap pot back into the double boiler. Check it for separation again after 10 more minutes.
Cook the mixture for a total of 3 hours, stirring the paste for a few minutes every 30 minutes. You will notice a change in the color of the paste as time goes by. It will become more and more transparent.
Check for free fatty acids- After 3 hours of cooking, remove 1 oz. of paste and mix it with 2 ounces of distilled water. Allow this to cool. If the cooled sample is extremely milky in appearance, it contains free fatty acids and needs to be cooked longer. If it is milky is appearance, cook for another 30 minutes and check it again.
Remove the soap pot from the double boiler and place it directly over medium heat on the stove. Now, using the gel recipes we have included on the bath and body recipe page, add 8 oz. of Isopropyl Alcohol and 24 oz. of glycerin. You will also want to add 4 Tablespoons of 33% borax solution in order to neutralize the mixture. (33% Borax solution is achieved by mixing 3 oz. borax to 6 oz. boiling distilled water).
Cook the paste, alcohol, and glycerin together over medium heat and stir until the paste is completely dissolved. If you have problems getting the paste to dissolve, add a few extra ounces of alcohol.
After the mixture has dissolved, add 36 oz. of distilled water. Weigh your entire soap pot. Write this weight down. Continue to cook the mixture until the mixture appears to be heavy. Weigh your soap pot, and if you notice a decrease of 12-16 oz. , test the viscosity of the mixture.
Remove the pot from the stove and remove a small sample of the gel from the soap pot. Place this sample on a cool surface and allow to cool. If the sample is watery after it cools, cook the mixture until another 3 more oz. of weight are gone. Test the viscosity again.
Once you reach the desired viscosity, you will want to add dye, additives and fragrance to your gel quickly and pour it into bottles. Waiting too long to pour the gel may make it hard to work with.