I've been planning for a longer time to make soap myself. We still have a piece of self-made soap made by my great-grandmother -- it must be about 70 years old -- this was a time where supermarkets didn't exist yet. Back then, people made it from ingredients that were easily available: animal fat and ashes.
I have ordered some equipment and will experiment with making soap from fats/oils with NaOH. Before undertaking this, I wanted to know exactly how the chemical reaction works. There are many recipes and books available, but few of them explain the reasons for the recipes.
Before soaps were available, people apparently covered their skin with olive oil, rubbed it to dissolve the oily dirt, and then removed everything mechanically since water cannot wash away nonpolar substances. Soaps however are capable of making an emulsion from oily (apolar) as well as watery (polar) substances, which water can rinse away easily.
Making soaps can be an important skill if you don't want to rely on supermarkets, which in turn rely on the world economy.
Production of soap from fats was forbidden during World War I. All fat had to be reserved for human consumption. The soaps which were sold during that time actually consisted only of about 10% real fat-based soap with 90% worthless filling agents (like ceramic and earth dust). Purchasing of soap was strictly regulated and only possible with certificates issued by the state. So, I guess that during difficult times, soap (and the skill to make it) is valuable.
In emergency sitations you could make soap from fat/oils that are available to you but otherwise are inedible. Before throwing old fat away, one could make soap from it. There is a way to make purified soap from non-pure ingredients (via addition of table salt, see later on).
In chemical terms, a soap is a salt of a fatty acid. To get this salt, you have to make a chemical reaction between a fatty acid and a base (alkaline watery solution). Sources of fatty acids are any kind of plant oil (e.g. coconut, olive, etc.) or animal fat (e.g. tallow, lard, etc.). In nature, fatty acids do not appear as isolated molecules. Usually they are grouped together in a so-called triglyceride molecule. A triglyceride is a Glycerol molecule to which 3 fatty acid moleclues are attached.
The base in a watery solution tears away the fatty acids from the triglyceride molecule and reacts with them. Bases which are most popular for making soap are:
* Potassium Hydroxide (KOH). It can be leached out of wood-burning ashes by repeatedly pouring the same water over it and collecting the enriched water. Traditionally this has been called Lye, although "Lye" is a broad and loose term that today is rather used for NaOH in solid form. KOH produces liquidy and softer soaps than NaOH. Traditionally, the water was repeatedly poured over the ashes until an egg would float on top of the mixture. This was an indicator that the concentration of alkali components was high enough to produce soap.
* Sodium Hydroxide (NaOH). This is a more potent base than KOH and therefore produces harder soaps. An alternative name is "Caustic Soda" and "Lye". It is sold as white, solid chips and available in bulk in stores and even on Amazon.
The proportion of the amounts of fat and NaOH is important. Ideally all available fatty acid molecules will react with all available lye molecules, with no molecules left 'unreacted' on either side. If there is too much fat, the soap becomes too oily. If there is too much lye, the soap becomes too alkaline which might cause skin irritations. The amount of NaOH for a specific amount, type and mixture of fats must either be calculated by hand, or be looked up in so-called saponification tables. I found this online calculator, it even lists animal fats and produces nice recipes:
_http://www.soapcalc.net/calc/SoapCalcWP.asp
Out of curiosity, I made a manual calculation for the required amount of NaOH for the complete saponification of 1kg of lard and successfully verified the result from the online calculator.
For those who are interested, here is the manual calculation.
For each fatty acid molecule, one NaOH molecule is needed. This means that if you want to process 3 moles of fat, you need 3 moles of NaOH. To convert the number of moles to grams, you need to know the molecular weights of each fatty acid which can be found in lard.
Lard consists of (see paper for the quantities):
Oleic Acid 47 %
Palmitic Acid 26 %
Stearic Acid 14 %
Myristic Acid 3 %
Palmitoleic Acid 3 %
Linoleic Acid 3 %
The molecular masses are (from Wikipedia):
For 1 kg of lard, you get the following molecule amounts (multply 1000 g * molecular mass * percentage):
So, 1 kg of lard has in sum 3.53 mol of fatty acids. To make soap from it, you need the same amount of NaOH, also 3.53 mol.
The molecular mass of NaOH is 40 g/mol. It follows that 3.53 mol of NaOH equals 141 g of NaOH. This is the theoretical amount required to saponify 1000 g of lard. This matches with the result that the online calculator produced. :D
KOH's weight is 56.1 g/mol, so if you want to use KOH (e.g. from ashes), you have to use about 40 weight percent more than NaOH.
Amongst the traditional methods there are 3 different variations of making soap:
Cold process
1. Measure NaOH and fat weights exactly
2. Wear thick rubber gloves and eye/face protection! NaOH is very corrosive! Slowly mix the NaOH with water (a good starting point seems to be: water 70 weight-percent, NaOH 30 weight-percent). This is an exothermal reaction and will heat the water considerably. Danger of overboiling, explosion and injury if not done slowly and carefully!
3. Heat the fat to about 60°C (140F)
4. Bring the NaOH solution to the same temperature
5. Pour the NaOH solution into the fat and mix with a hand-held blender thoroughly, keep temperature at 60°C while doing this
6. The mixture will start to solidify slowly. Optionally add color, parfume or essential oils (this should be done as late as possible since the NaOH could react with the essential oils and rendering them inactive)
7. Pour everything into a mold and let it cool to room temperatur
8. On the next day, take the hard soap out of the mold, cut it into pieces.
9. At this point, the chemical reaction is not complete. It will continue to react for 2-3 weeks. That is the reason why you have to let the soap pieces mature and dry. If you use it too early, it will be too alkaline.
In this process, the Glycerine (from which the fatty acids were split off) will still be in the soap. Glycerine is hydrophile and it is said to make the skin softer because it draws water into the skin.
Hot process
This is identical with the cold process, steps 1-5. However you continue heating the mixture to 80-100°C until saponification is complete. The advantage is that the soap is immediately ready for use, no maturing needed. The disadvantage is that as soon as the soap is poured into mold and it cools down, it hardens immediately.
Hot process + purification
Purification helps to draw out of the soap any kind of impurities. This is advantageous when low-quality (used) fat is used. It is otherwise identical to the Hot Process, except that a handful of table salt is added to the mixture. The salt will draw out the excess water from the mixture (taking the Glycerine, excess NaOH and other water-soluble molecules with it) which will sink to the bottom of the pot. The purified soap will float on the top of the water, which then can be extracted with a sieve or piece of cloth.
I have ordered some equipment and will experiment with making soap from fats/oils with NaOH. Before undertaking this, I wanted to know exactly how the chemical reaction works. There are many recipes and books available, but few of them explain the reasons for the recipes.
Before soaps were available, people apparently covered their skin with olive oil, rubbed it to dissolve the oily dirt, and then removed everything mechanically since water cannot wash away nonpolar substances. Soaps however are capable of making an emulsion from oily (apolar) as well as watery (polar) substances, which water can rinse away easily.
Making soaps can be an important skill if you don't want to rely on supermarkets, which in turn rely on the world economy.
Production of soap from fats was forbidden during World War I. All fat had to be reserved for human consumption. The soaps which were sold during that time actually consisted only of about 10% real fat-based soap with 90% worthless filling agents (like ceramic and earth dust). Purchasing of soap was strictly regulated and only possible with certificates issued by the state. So, I guess that during difficult times, soap (and the skill to make it) is valuable.
In emergency sitations you could make soap from fat/oils that are available to you but otherwise are inedible. Before throwing old fat away, one could make soap from it. There is a way to make purified soap from non-pure ingredients (via addition of table salt, see later on).
In chemical terms, a soap is a salt of a fatty acid. To get this salt, you have to make a chemical reaction between a fatty acid and a base (alkaline watery solution). Sources of fatty acids are any kind of plant oil (e.g. coconut, olive, etc.) or animal fat (e.g. tallow, lard, etc.). In nature, fatty acids do not appear as isolated molecules. Usually they are grouped together in a so-called triglyceride molecule. A triglyceride is a Glycerol molecule to which 3 fatty acid moleclues are attached.
The base in a watery solution tears away the fatty acids from the triglyceride molecule and reacts with them. Bases which are most popular for making soap are:
* Potassium Hydroxide (KOH). It can be leached out of wood-burning ashes by repeatedly pouring the same water over it and collecting the enriched water. Traditionally this has been called Lye, although "Lye" is a broad and loose term that today is rather used for NaOH in solid form. KOH produces liquidy and softer soaps than NaOH. Traditionally, the water was repeatedly poured over the ashes until an egg would float on top of the mixture. This was an indicator that the concentration of alkali components was high enough to produce soap.
* Sodium Hydroxide (NaOH). This is a more potent base than KOH and therefore produces harder soaps. An alternative name is "Caustic Soda" and "Lye". It is sold as white, solid chips and available in bulk in stores and even on Amazon.
The proportion of the amounts of fat and NaOH is important. Ideally all available fatty acid molecules will react with all available lye molecules, with no molecules left 'unreacted' on either side. If there is too much fat, the soap becomes too oily. If there is too much lye, the soap becomes too alkaline which might cause skin irritations. The amount of NaOH for a specific amount, type and mixture of fats must either be calculated by hand, or be looked up in so-called saponification tables. I found this online calculator, it even lists animal fats and produces nice recipes:
_http://www.soapcalc.net/calc/SoapCalcWP.asp
Out of curiosity, I made a manual calculation for the required amount of NaOH for the complete saponification of 1kg of lard and successfully verified the result from the online calculator.
For those who are interested, here is the manual calculation.
For each fatty acid molecule, one NaOH molecule is needed. This means that if you want to process 3 moles of fat, you need 3 moles of NaOH. To convert the number of moles to grams, you need to know the molecular weights of each fatty acid which can be found in lard.
Lard consists of (see paper for the quantities):
Oleic Acid 47 %
Palmitic Acid 26 %
Stearic Acid 14 %
Myristic Acid 3 %
Palmitoleic Acid 3 %
Linoleic Acid 3 %
The molecular masses are (from Wikipedia):
Code:
Oleic Acid 282.46 g/mol
Palmitic Acid 256.42 g/mol
Stearic Acid 284.48 g/mol
Myristic Acid 228.37 g/mol
Palmitoleic Acid 254.41 g/mol
Linoleic Acid 280.45 g/molFor 1 kg of lard, you get the following molecule amounts (multply 1000 g * molecular mass * percentage):
Code:
Oleic Acid 1.66 mol
Palmitic Acid 1.01 mol
Stearic Acid 0.49 mol
Myristic Acid 0.13 mol
Palmitoleic Acid 0.12 mol
Linoleic Acid 0.11 molSo, 1 kg of lard has in sum 3.53 mol of fatty acids. To make soap from it, you need the same amount of NaOH, also 3.53 mol.
The molecular mass of NaOH is 40 g/mol. It follows that 3.53 mol of NaOH equals 141 g of NaOH. This is the theoretical amount required to saponify 1000 g of lard. This matches with the result that the online calculator produced. :D
KOH's weight is 56.1 g/mol, so if you want to use KOH (e.g. from ashes), you have to use about 40 weight percent more than NaOH.
Amongst the traditional methods there are 3 different variations of making soap:
Cold process
1. Measure NaOH and fat weights exactly
2. Wear thick rubber gloves and eye/face protection! NaOH is very corrosive! Slowly mix the NaOH with water (a good starting point seems to be: water 70 weight-percent, NaOH 30 weight-percent). This is an exothermal reaction and will heat the water considerably. Danger of overboiling, explosion and injury if not done slowly and carefully!
3. Heat the fat to about 60°C (140F)
4. Bring the NaOH solution to the same temperature
5. Pour the NaOH solution into the fat and mix with a hand-held blender thoroughly, keep temperature at 60°C while doing this
6. The mixture will start to solidify slowly. Optionally add color, parfume or essential oils (this should be done as late as possible since the NaOH could react with the essential oils and rendering them inactive)
7. Pour everything into a mold and let it cool to room temperatur
8. On the next day, take the hard soap out of the mold, cut it into pieces.
9. At this point, the chemical reaction is not complete. It will continue to react for 2-3 weeks. That is the reason why you have to let the soap pieces mature and dry. If you use it too early, it will be too alkaline.
In this process, the Glycerine (from which the fatty acids were split off) will still be in the soap. Glycerine is hydrophile and it is said to make the skin softer because it draws water into the skin.
Hot process
This is identical with the cold process, steps 1-5. However you continue heating the mixture to 80-100°C until saponification is complete. The advantage is that the soap is immediately ready for use, no maturing needed. The disadvantage is that as soon as the soap is poured into mold and it cools down, it hardens immediately.
Hot process + purification
Purification helps to draw out of the soap any kind of impurities. This is advantageous when low-quality (used) fat is used. It is otherwise identical to the Hot Process, except that a handful of table salt is added to the mixture. The salt will draw out the excess water from the mixture (taking the Glycerine, excess NaOH and other water-soluble molecules with it) which will sink to the bottom of the pot. The purified soap will float on the top of the water, which then can be extracted with a sieve or piece of cloth.
(I'm interested to know)?
