1. What do the "'One" and "All"columns on the left mean? GoTo


2. What are the best values for Hardness, Cleansing, Condition, Bubbly and Creamy? GoTo


3. I'm not sure what the ideal "Water as % of Oils"would be for any given soap recipe? GoTo


4. What is superfat or discount? GoTo


5. Why is a minimum 5% discount recommended? GoTo


6. What is milk fat (bovine)? GoTo

The "One" column displays the soap qualities and fatty acid percentages of the individual oil/fat selected in the center column. Notice that as you click on each oil, the numbers in the "All" column change to represent the qualities for that oil.  The numbers in the "Individual" column will always display the qualities of the oil currently selected in the oil list, even after clicking "Calculate Recipe".

The "Combined" qualities display the soap qualities and fatty acid percentages of all the oils listed in your recipe (the right column). These are displayed after you click "Calculate Recipe".  If you change an oil in your recipe or change a percent, "Calculate Recipe" must be clicked again to update the numbers in the "Combined" column.

When you place your mouse over the soap quality for a moment (Hardness, Cleansing, Condition, etc.), a little box will show a suggested range of values. The suggested range of values is also displayed with the graph on the View Recipe page. These are guidelines; it's OK to go above or below these values a little. For more information please see the Soap Qualities page.

The water in your recipe is required to separate the oils and fats into fatty acids and glycerine. This process, involving both the water and the lye is called hydrolysis and makes the fatty acids available to react with the lye and make soap. Most, but not all, of the water evaporates during the soap making process. More water is required for making soap at higher temperatures than at lower temperatures.

The calculator provides the percentage of lye in the water and lye solution. It also presents this value as the 'Water:Lye' ratio. There is no "right or ideal" number to choose for water as a percentage of the total amount of oils. However, when the lye is greater than 40% of the water and lye solution, the hydrolysis process may not be complete and your soap may end up with some lye in it.

The calculator has a default value of 38%.  It's a safe starting point and will make a decent bar of soap for both CP and HP. You can experiment from there.

Caution: Lye solutions with higher concentrations of lye will speed up the chemical process.  Your oil and lye solution mixture could easily bubble out of the pot and spill over your stove or table (or you). This happens quickly.   It is commonly called the volcano effect.  Beginners should start with the default 38% "Water as % of Oils".   more information

Tip: Keep a long spatula handy. If a volcano starts, immediately run the spatula rapidly back and forth edgewise through the mixture. I have found this technique useful for keeping a volcano within the pot. Of course, it is good practice to use a pot large enough so that the mixture is comfortably contained in less than ½ the pot.

If you use all the lye necessary to exactly saponify all of the fatty acids in the oils, the soap would have no excess lye or excess oil (next to impossible without a chemistry lab). It would have a zero discount and there would be no superfat.  If you discounted the lye, let's say by 5%, 5% of the soap would contain oils that have not chemically reacted with the lye.   i.e. all the lye was used up in reacting with 95% of the oils. The soap would have a 5% superfat. These unsaponified oils are good for conditioning the skin. A soap with no discount or superfat will clean better. However, other than conditioning the skin, there are other important reasons to discount the lye (or superfat the soap).  Please see the next question.

Go to Top

The SAP values used to calculate the amount of lye - in this calculator and in others - is an average. If you purchase oils/fats that have been assayed by a chemical lab, you will know the exact SAP value of the oils/fats. (Your wallet will be a little thinner too).  If you weigh these oils and the lye on very precise labratory scales, you can confidently make a true zero discount soap.

One of my references gives the Potasium Hydroxide (chemical symbol KOH) SAP value for coconut oil as 250-264.   The SAP for other oils is specified similarly as a range of values. Why? There are many variables that contribute to the chemical qualities of a carrier oil. Here are a few to give you the general idea:

• Species of the botanical used to make the oil.
• Geographical location of the source botanical. i.e. variable climate.
• Varying types of processes used to create the oil.
• Seasonal differences in when the botanical was harvested.
• Maturity of the botanical when it was harvested.

The minimum 5% discount/superfat is recommended to allow for these variances so you do not end up with soap that contains unused lye.

It is not butter, half and half, or heavy cream. It is the pure cream contained in those products.  It is made by spinning natural whole milk (straight from the cow or other bovine animal) in a centrifuge like device.  Some soapers have access to natural whole milk and can buy a cream separator or can buy milk fat from a local dairy.  Heavy cream has a fat (cream) content of between 36% and 40%.

Check these links for more info:

Cream Separator
Butter Manufacture
Cream Separator
What is Heavy Cream?