What is a lye calculator?
A lye calculator allows you to develop and test your own recipes by telling you how much lye to use with the oils you have selected. You can also use a lye calculator to doublecheck a recipe you have selected from a book or the web before using it.
Why is it necessary?
Different oils have different amounts of fatty acids and unsaponifiable material. That means that different amounts of lye are required to produce saponification. The lye calculator will allow you to determine the correct amount of lye for your recipe.
How do I use the lye calculator?
Write out a list of oils you intend to use in your soap and the amounts (in ounces) you intend to use (Step 1 in the example below). Now multiply the number of ounces being used by the sap value of the oil (see Step 2). Total your list of figures to get the total amount of lye necessary to saponify your soap (Step 3). However, most soapmakers prefer to automatically superfat their soap by 5%. This is done by reducing the lye by 5% - also called discounting the lye (Step 4). Now calculate the amount of water needed for the recipe by dividing the total ounces of oils used by 3 (Step 5).
Here is an example of the lye calculator in action with my super duper moisturizing bar for very dry skin. Feel free to use this recipe, for personal use.
Castor Oil 2 oz
Cocoa Butter 2 oz
Coconut Oil 4 oz
Olive Oil 6 oz
Palm Oil 6 oz
Avocado Oil 3 oz
Apricot Kernel Oil 2 oz
Castor Oil 2 x .1286 = .2572
Cocoa Butter 2 x .137 = .274
Coconut Oil 4 x .190 = .76
Olive Oil 6 x .134 = .804
Palm Oil 6 x .141 = 0.846
Avocado Oil 3 x .133 = .399 Apricot Kernel Oil 2 x .135 = .27
3.6 ounces lye necessary to saponify the soap.
3.6 x .95 = 3.4 ounces lye Step 5 25 ounces oil divided by 3 = 8.3 ounces water. Things to remember: * Double, even triple check your calculations. * Lye calculators which automatically calculate lye and water for you can be found on the web.
If you have troubles with math, then here are some links that can help you.
1.) SoapCalc http://www.soapcalc.com/default.asp
Description: This site offers a wide range of possibilities, the user is able to enter ingredients as a weight or percent as well as adjust properties of the soap such as super fat/discount %. This site has loads of useful information, one link I found particularly useful when i was first starting out was the "what will I need" link, which gives the inexperienced soaper a concise list of supplies needed to start soaping with.
2.) 'Majestic Mountain Sage' lye calculator http://thesage.com/calcs/lyecalc2.php
Description: In this calculator, users are able to input the amount of oils in percent of total oils, there are also clickable links leading to oil properties as well as suggested amounts of use in recipe's. This site also includes a table after the recipe is calculated that lets the user choose a super-fat percent to be used in the recipe.
3.) SoapMaker http://www.soapmaker.ca/
Description: Note: this is a free trial, users must purchase the full program after trial period expires. "Create your own recipes, selecting from more than 50 types of base oils. Include your additives too. SoapMaker calculates lye and water, as well as the cost per bar using your ingredient costs. Experiment with recipes and see how they'll turn out before you make the soap... SoapMaker's unique recipe qualities graph shows you the predicted hardness, lather and moisturizing qualities. Compare different recipes and see the results of changes instantly using the dynamic graph feature .Store all your recipes and organize them by category, type, date and cost With SoapMaker Professional, manage your stock of ingredients and products made... your inventory adjusts automatically whenever you "make a batch" (quoted from soapmaker website" )
4.) Snowdrift Farms http://www.snowdriftfarm.com/soapcalculator.htm
Description: The lye calculator from this site has many useful tools, users can choose what type of soap to make (either liquid or solid) as well as whether or not to make the recipe a cream soap. Users can also select their measurement preferences for the calculation. This site offers instructions as well (through the links on the bottom left of the page) for making either liquid soaps, solid bar soaps or cream soaps! A valuable tool for any soaper!
5.) Maple Springs (added by Paul) http://www.maplesprings.com/soapcalc.html
Description: "To use the Maple Springs Farm soap lye calculator... simply enter in number of ounces per oil and the amount of lye, water, fragrance, and pigments will be automatically calculated for you...The Calculator is for Sodium Hydroxide = NAOH " This site is quite useful, it gives feedback regarding the size of the recipe as well as how many ounces of essential oils, and oxide/pigments are recommended for the given recipe size. This is quite a valuable tool to if you input recipes that have already been formulated to determine the right coloring amounts and essential oils, or formulate your own!
6.) J.Soule Web Design http://www.jsoule-webdesign.com/soapcalc/
Description: This calculator is also a valuable resource, users can enter a recipe name, choose base oils, super-fatting oils, and whether NaOH or KOH is to be used in the recipe. It also allows users to input the liquid of choice, and calculate the recipe in oz, lb, or grams. The user has a choice of up to 8 base oils and 3 super-fatting oils. This will also give you the amount of water left in the soap after cure! a valuable fact for any soaper to know about the soaps they produce! There is also a helpful list of oil properties that is alphabetized and comments on Hard Bar, Lather ,Conditioning, and Iodine values.