How to Make? An Improved Soap .. Not just for more Foam (GTZ, 1993, 71 p.) A. Basic elements for making improved soap A.I. Raw materials A.II. Technology of improved soaps making

How to Make? An Improved Soap .. Not just for more Foam (GTZ, 1993, 71 p.)

A. Basic elements for making improved soap

A.I. Raw materials

The raw material needed for making soap are fats (oil, grease or butter), alkaline, water and secondary products (salt, additive colors, scents etc.).

A.I.1. Fats

A.I.1.1 Nature and chemical characteristics

The natural fats used for soap making are triglycerol, which is an ester from an alcohol triple, glycerol with linear carbonic acid chains (fatty acid). According to their solidity at ordinary temperature, fats divide into oils (liquid at usual ambient temperatures) and butters (solid).

Some fats are extracted from plants while others are animals origin. On the chemical point of view, all are appropriate for saponification. However more or less fundamental differences exist between the proprieties of each of them. In the practice the number of fats used for soap production is limited. The main reasons for this limitation are economic and technical proprieties of fats and of the soaps generated from them, availability and price.

There exists two (2) main chemical parameters to characterize the appropriateness of triglycerol for saponification: Iodine Number and Saponification Value.

The Iodine Number of a fat expresses the weight of iodine in grams which can be fixed from 100 g of them. It indicates the presence of double links, thus the degree of insaturation of the carbonic chain.

Its value varies between 10 to 200. Note that the butters and greases, which are solid under normal conditions , have an Iodine Number inferior or equal to 70. Moreover the soap made from a high Iodine Number fat has the tendency to be soft. The Saponification Value of a fat is the quantity of caustic potassium (KOH) in mg needed to transform 1 g of it in soap. For most of the natural triglycerol, this index is situated at about 190-200. The important exceptions concern palmist, copra and cowbutters with value reaching 240-250. A high Saponification Value indicates an easier transformation of the fat into soap.

In soap making process iodine number and saponification value play an important role in a sense that their values allow to predict some important proprieties of the soap obtained from the fats (or the mixture of fat).

The INS Factor (Iodine Number-Saponification Value), which represents the difference between these indexes, is an essential parameter enabling to characterize as well the (mixture of) fats as the soap obtained from the latter.

With increasing values of this factor, the following proprieties can be observed:

1. The fat tends to be solid;
2. The soaps made are tough (rough);
3. The bleaching and foam forming proprieties tend to decrease
4. The solubility of soaps tend to decrease;
5. The soaps tends sharply to become rancid.

Copra and palmist fats constitute the exceptions to the above stated rules.

Table I. indicates the values of iodine and saponification indexes of the main fats used in soap making in tropical areas.

The majority of these fats are plant origin and are extracted from cultivated plants. However in certain rural areas, a high proportion of fatty materials used in traditional soapmaking are extracted from fruits of wild plants.

In Sahel and Savanna Zones, the following wild species are used in soap making: Balanites aegyptiaca, Karitea (shea) (Byturospermum parkii), Cailcedra (Khaya senegalesis), Manan (Lophira lanceolota), Baobab (Adansonia digitata) etc.

Some essential using proprieties of an improved soap strongly depend on the nature of the fat being used for its composition.

Table II. indicates some important characteristics of soaps from selected fats

Table I. Iodine number and saponification values, INS Fac of principal fats used in soap making in tropical zone; weight of caustic soda to saponify 1 kg

FATS	SAPONIFICATION VALUE	IODINE NIMBER	INS FACTOR	CAUSTIC SODA NEEDED TO SAPONIFY 1 kg (in g)
Butters/Fats
Cocoa	195	38	157	1339,03
Coprah	256	8	248	1882,53
Karitea	187	61	126	1333,33
Fat (pork)	198	70	128	141,17
Tallow (cow)	197	40	157	140,46
Tallow (mutton)	195	39	156	139,03
Oils
Peanuts	190	95	95	1335,47
Baobab	206	27	179	1446,88
Cotton	194	109	85	1338,32
Kobi	195	71	124	1339,03
Kapok	193	83	110	1337,61
Manan	191	70	121	1336,18
Neem	196	69	127	1339,73
Palm	200	51	149	1442,60
Palmist	248	17	231	1776,82
Physic oil	196	92	104	139,75
Castor oil	182	85	97	127,77
Sesam	190	111	79	1335,47
Soja	192	128	64	1336,90
Sunflower	190	135	55	1335,47

Baobab (Adansonia sp.), Kobi (Carapa sp.), Kapok (Eriodendron s and Manan (Lophira sp.), are wild species of humid and semiarid tropical zones.

Table II. Characteristics of sodium soaps from the main soap making fats in tropical zone

Soap from	Colour	Consistency	Foaming capacity Foam characteristics	Bleaching effect	Effect on the skin	Usage
Butters/Fats
Coprah	Pale yellow to white	Very hard Crumbly	Strong, quick, foam less stable	Very good even at cold	Rough	Washing
Karitea	White	Hard	Slow	Middle	Very soft	Body hygiene, Washing
Fat	White	Hard	Strong, quick stable foam	Good	Very soft	Body higiene
Tallows	White to yellow pale	Very hard	Weak, slow, stable foam	Good	Very soft	Body hygiene, Washing
Oils
Peanut	Tan	Quite hard	Weak, slow	Middle	Very soft	Body hygiene, Washing
Cotton	Grey-yellow	Soft	Middle, stable foam	Good	Smooth	Washing
Manan	Tan	Hard	Strong, stable foam	Good	Smooth	Washing, body hygiene
Neem	Dirty yellow	Hard	Strong, quick, stable foam	Very good	Smooth, antiseptic	Washing, body hygiene
Palm	Yellow pale	Hard	Strong, slow foaming, stable foam	Very good	Very smooth	Body hygiene, Washing
Palmist	Yellow pale	Very hard (Crumbly)	Strong, quick, foam less stable	Very good even at cold	Rough	Washing
Pourghere	White pale	Soft	Strong, quick, foam stable	Good	Smooth, antiseptic	Washing, body hygiene
Castor-oil	White	Very hard	Weak, foam stable	Good	Smooth	Washing, body hygiene
Sesam	Brown-clear	Soft	Strong, slow, foam stable	Good	Smooth	Washing

A.I.1.2 Pretreatment

The usual techniques for extraction generate fat products containing impurities. Moreover these fats present sometimes, at raw state, strong odors and more or less intense colorations. Soaps produced from such raw materials are least quality.

To obtain a good appearance and better usage quality soap from such materials, the precedent refining and bleaching are consequently necessary. To achieve this, there are some simple methods.

A simple method of refining (purification and deodorisation) consists in boiling the fat in mixture with water during 5 h at least (one volume of fat for 1/2 a volume of water).

The addition of some natural products can considerably improve the performances of this method, for instance that of a mixture from okra powder (hibiscus esculentus). At the end of the operation, the impurities pass into the watery phase and the purified oil floods above.

A modification of this techniques consists in boiling the fat with 25% of its weight from a solution of 10% salt in water during 30 minutes.

The bleaching (decoloration) is also necessary as pretreatment method of some soap making fat with initial strong coloration.

Palm-oil, and in a less measure, that of cotton, should go through this stage before their saponification. The simple bleaching methods we can consider are as follows:

- Thermic treatment (oxidation at hot air);
- Bleaching by adsorption on special muds targile, kaolin) or/and activated charcoal;
- Chemical bleaching with strong oxides.

Thermic bleaching is achieved by boiling the fat body to 200-250 °C in a basin opened during 5 to 6 hours. The operation is carried until a white paper dipped into the oil doesn't show any more coloration.

As for bleaching by adsorption, the fat is boiled at 90 - 100 °C; you then add around 5% of its weight in adsorbent muds (and eventually 1 to 2% of active charcoal). The product is mixed during 15 to 20 minutes.

The chemical bleaching is made with potassium bichromate (1 to 2 %) in presence of a strong mineral acid (H₂SO₄ or diluted HCl). The temperature of the mixture should be maintained under 52 °C.

So this operation is thus somewhat more delicate than the two precited others.

A.I.2. Alkali

For direct saponification of neutral fats (triglycerols) we need to put a strong basic solution (alkali) in the water. Caustic soda and caustic potasch are the most frequently used for this goal. The soaps obtained from these two bases are however different in some characteristics such as consistency, foam formation, solubility etc.

A.I.2.1. Caustic soda (NaOH)

This is the most alkali used for saponification of neutral fat. The soaps obtained (sodium soaps) are harder and less soluble than those obtained from potassium. Moreover they are less able to retain the humidity of the air.

The caustic soda is a chemical basic product used in various fields of crafts: tanning, dying etc. So it is easily available on the market, even in developing countries.

At pure natural stage, it is a white crystallin substance, which is easily soluble in water with heat production. The concentrated caustic soda solutions are harmful to the skin and can cause serious burns. They should consequently be handled cautiously.

The caustic soda solution quickly retains the carbondioxid from the air, which leads to a change in the initial concentration. For this reason, usage of the densimeter enabling the determination of exact concentration of the alkaline solution available for saponification, is necessary.

To prepare the caustic soda solution by using the solid product from the market, you dibite the quantity of soda in the same weight of water (add small portions of the product to water by stirring well). Be cautious by wearing protecting glasses and gloves.

FOR SECURITY REASON, NEVER PRACTICE THE ABOVE MENTIONED OPERATION IN THE ADVERSE SENSE, BY POURING WATER ON CAUSTIC SODA !

The basic solution so obtained can be easily diluted by water addition and usage of a densimeter to control progression of the dilution. You so obtain the concentrated solution required for the chosen saponification process.

A simple and approximate method to determine the concentration of an alkaline solution consists in putting into it an egg of chicken. When this just floats over the surface, the solution contains respective:

180 g of caustic soda (NaOH)
230 g of caustic potassium (KOH)

for each liter.

Table III. gives the density and corresponding concentration levels of caustic soda and potassium solutions.

Table III: Density and concentration in free alcali of caustic soda (NaOH) and potassium (KOH) solutions

Degre Baume (°Be)	Density at 15°C	1L of solution contains:		1Kg of solution contains:
		(g NaoH)	(g KOH)	(g NaOH)	(g KOH)
1	1,007	6	9	6,,100	9
2	1,014	12	17	122,000	17
3	1,022	21	26	200,000	26
4	1,029	28	36	277,100	35
5	1,036	35	46	333,500	45
6	1,045	42	58	400,000	56
7	1,052	49	67	466,400	64
8	1,060	56	78	522,900	74
9	1,067	63	88	588,700	82
10	1,075	70	99	655,500	92
11	1,083	79	109	733,100	101
12	1,091	87	119	800,000	109
13	1,100	95	132	866,800	120
14	1,108	104	143	944,200	129
15	1,116	112	153	1000,600	138
16	1,125	123	167	1009,700	148
17	1,134	134	178	1118,400	157
18	1,142	144	188	1226,400	165
19	1,152	156	203	1335,500	176
20	1,162	167	216	1443,700	186
21	1,171	177	228	1551,300	195
22	1,180	188	242	1559,100	205
23	1,190	200	255	1667,700	214
24	1,200	212	269	1776,700	224
25	1,210	225	282	1885,800	233
26	1,220	239	295	1995,800	242
27	1,231	253	309	2005,900	251
28	1,241	266	324	2114,200	261
29	1,252	283	338	2226,400	270
30	1,263	299	353	2336,700	280
31	1,274	316	368	2448,100	289
32	1,285	332	385	2558,000	298
33	1,297	348	398	2668,300	307
34	1,308	364	416	2778,000	318
35	1,320	384	432	2888,300	327
36	1,332	399	449	2999,300	337
37	1,345	420	469	3112,200	349
38	1,357	441	487	3224,700	359
39	1,370	462	506	3336,900	369
40	1,383	483	522	3449,600	378
41	1,397	506	543	3662,500	389
42	1,410	528	563	3774,700	399
43	1,424	553	582	3888,000	409
44	1,438	575	605	3999,900	421
45	1,453	602	631	4114,100	434
46	1,468	629	655	4228,300	446
47	1,483	658	679	4443,800	458
48	1,498	691	706	4661,500	471
49	1,514	721	731	4766,000	483
50	1,530	750	756	4900,200	494

In general, 13 to 15% of the weight of the fat are necessary for saponification with caustic soda. The concentration of the alkaline solution to be used can vary between 8 and 50% according to the preparation method which is used.

Examples showing how to calculate the quantity of caustic soda solution needed for saponification by using the saponification value and the Baune-densimeter.

The among of caustic soda necessary for complete saponification of a fat is obtained by using the following formula:

(Weight of fat (Kg) X saponification value X 0,713) / 1000

where

0.713 = ratio of molar masses of caustics soda and potassium (40 g: 50,1 g = 0.713) and
1000 = conversation factor from grams into kilograms.

To saponify for instance 5 Kg of peanut oil, you need:

For a mixture of fat, the easiest method consists in calculating the respective quantities for complete saponification of each component.

The addition of these values finally gives the total quantity of soda for saponification of the mixture.

Example: 100 Kg of a fat mixture composed of:

cotton oil	30 Kg
palm oil	30 Kg
karitea (shea) butter	40 Kg

For saponification of the various component, the following quantities of caustic soda are needed:

Cotton oil:

Palm oil

Karitea butter:

Total = 13,76 KG

When you use an alkaline solution, the quantity needed for saponification is obtained as follows:

The exact concentration of the alkaline solution is obtained by measuring the density of the liquid with a Baume aerometer.

Knowing the degree of the solution and based on indications in Table III, you can determine the quantity of pure caustic soda contained in 1 Kg (or in 1 l).

Example:

The precedent mixture of 100 Kg needed, as noticed, 13,76 Kg of pure caustic soda for a complete saponification.

By using a solution at 24 °Be, the total quantity of that solution for a complete saponification will be:

A.I.2.2 Caustic potassium (KOH)

It is a strong base, which like caustic soda, allows direct saponification of neutral fats. As the latter, the concentrated solutions can cause serious burns on the skin. Caustic potasse is less currently used at home level than soda. So it's less available on the market.

However the home-soap-making uses it most exclusively as alkaline source in rural zones. For this purpose you treat vegetable ashes with water. Potassium made soaps are quite soluble in water and present a bright ability to adsorb it (hydroscopy). They are thus of soft consistency and even liquid.

A.I.3. Water

The reaction environment for saponification is an emulsion between fat and water, in which the needed alkali is diluted. Appropriate water for soap making is soft water (rainwater for instance), as hardness elements of water, the magnesium and calcium ions present the propriety of deleting the washing action of soaps.

An easiest method for softening a hard water consists in adding concentrated alkaline solution, mixing it well and left still for 1 to 2 days. The Mg and Ca ions will then form in water insoluble byproduct that deposit at the bottom of the container

A.I.4. Secondary products

The secondary products used for making improved soap are: salt, additives (clay, kaolin,starch, silicate, carbonate etc). Usage of these products is not strictly necessary for soap making, but they can present some technical and trading advantages(improvement of usage qualities, decrease in production costs for instance).

A.I.4.1. Salt

Addition of salt to soda soap leads to achievement of very hard soaps. This practice is based on the fact that soap is not soluble in salted water. Glycerine which is soluble in water is than eliminated with other impurities of the raw materials. Soaps obtained from some fat like copra, palmist or castor oils can incorporate high quantities of salt without being greened out. In this case salt can be used as filling material.

The quantity of salt to be added for greening out varies according to the nature of the fat and is about 10 g of salt for each 100 g of original fat material. The main advantage of greening out is that it gives purified soap.

A.I.4.2 Additives

These products are added to soap in order to either increase the quantity or to give it a hard consistency. To that aim you can use clay or kaolin or starch or silicates of soda or potassium etc. The later can contribute to improvement of washing qualities of the soaps containing it and protect them also form becoming rancid. Other types of additives like alcohol, sugar and glycerine are used to produce transparent soaps. Kaolin can be added to an optimal rate of about 5% of the mass of the initial fat to be saponified.

A.I.4.3 Colors

The color of the product may be important for good selling. To achieve this, the home level soap maker may use some natural colors. Among them you can use the extracts from niebe leaves (vigna sp) for the green color and extracts from red sorgho (Sorghum sp) for colors going form red-brown to orange.

The extraction of these colors is made with diluted alkaline solutions. The process consists in putting mashed leaves in maceration in alkaline solution until you achieve the color you wish. The obtained liquid can be used after filtering.

Non bleached palm oil also can be used (after being filtered) for colorations from light-yellow to orange.

According to local availability, other natural colors can be used. They should how ever be stable to alkaline and oxidation.

The above mentioned extracts should be incorporated to the hot mass of soap at the rate of 0,l to 5% of the initial fat weight.

A.I.4.4 Scents

In order to give a scent to the soap, the soap maker may use extracts from local plants containing perfumes (etheric oils). Extracts from citronel and lemongrass (Cymbopogon sp.), Eucalyptus (Eucalyptus sp) etc. are appropriate.

The extraction itself is a simple process which is done with steam according to the following scheme:

Installation of steam distillation of etheric oils

- Putting water into containers I and II (metallic containers of 50 1 for example);
- Heating intensively container I and moderately container II;
- After bringing containers I to boil, put the smashed vegetable material in container II;
- Put in place a vase to recuperate the liquid of condensation, connect the tube for condensation and close hermetically the container II;
- Then connect I and II, close I hermetically and go on heating it intensively during about 15 minutes;
- After 15 minutes, stop the operation and recuperate the cloudy water of condensation.

The so achieved extract is incorporated into the soap by mixing it at rate of 1 to 100 g for 100 kg of raw fats.

A.I.4.5 Skin protecting agents

Soaps obtained from some fats are damageable to skin. These harsh side-effects are particularly valid for palmist and copra butter based soaps. For this reason addition of skin protecting agents to such soaps is necessary.

Among the natural products which can play this role by improved soaps you may consider: the portion of insaponifiable in the fat, a light surplus of non saponified fat (to be added for instance at the end of the operation) and addition of natural wax (about 3 - 5 % of beeswax for example).

A.II. Technology of improved soaps making

Soap fabrication from neutral fat (triglycerol) and alkali (for instance caustic soda, NaOH) is achieved according to the following reaction:

(RCOO)3C3H5	+	3NaOH	®	3RCOONa	+	C3H5(OH)3
Triglycerol	+	caustic soda	gives	soap	+	glycerol.

According to the conducting temperature of the saponification reaction, we distinguish three (3) different methods of soap-making: the saponification at cold temperature, the semi-hot saponification process and the hot process.

A.II.1. Cold saponification process

It is a simple process which requires less time and energy. Moreover the produced soap contains glycerine. This has a good effect on skin and can contribute to a better conservation of soaps during storage (prevention from dehydration). This soaps are well soluble and produce a lot of foam.

The main disadvantages of this method are:

- All fats are not usable for saponification according to that process, particularly some proportion of copra butter and/or palmist oil should be incorporated into the fats mixture;
- The soap produced contains all the impurities of the reaction mixtures;
- A surplus of free alkaline is necessary to prevent the rancidity.

Operating method:

The (mixture of) fat is heated in the boiler up to 40°C. Then You add the necessary alkaline solution tin small portions at the beginning), by stirring well in the same direction. By using caustic soda, the appropriate solution must have a concentration of 20 to 35% of NaOH (or about 26 to 40 °Be. By correct operating, the reaction produces enough heat to ensure a complete saponification.

The auxiliaries (additives, color, scent) are incorporated when the reaction has really started (the mixture then shows a consistency which looks like that of honey). The warm mass is then poured into big moulds where the complete saponification reaction is achieved.

A.II.2. Semi-hot process

This method of saponification is also easily to implement if you practice the following way:

- Heat fat (or mixture of fat) at about 55 - 70 °C;

- Add (slowly and in small portions at the beginning) the alkaline solution necessary to saponification by stirring (the reaction produces heat and the temperature of the mixture can increase up to 90°C)

- Leave the mass become cold to 60°C and mix in the auxiliaries;

- Pour the soap in containers (for 24 to 36 hours) and leave it until it becomes cold and hard.

The above mentioned cold and semi-hot processes are quite well indicated for improved soap-making at home and small-scale levels considering their easy implementation and the quality of the products they can generate

A.II.3. Hot or full boiling process

This method of saponification is mainly used for production of hard sodium soaps.

The implementation of operations is identical to that of semi-hot process until the real starting of soap formation (increased viscosity of the reaction medium). From this stage, you add by portions the remainder of the alkaline solution by stirring when being heated. After adding the calculated alkaline, you heat the mass up to ebullition during a few hours.

At the end of this operation practice, the graining out consisting in adding salted water or humid salt, must be carry out. The initial mass divides then into 2 phases: an inferior stage composed of salted water, glycerol and soluble impurities present in the mixture and a superior stage composed by the soap (insoluble in salted water).

The resulted soap undergoes again some special operations (cocking in a strong bleach, liquidation etc.) before being poured in moulds for hardening.

This process, when correctly executed can produce a soap of semiindustrial quality. According to its complexity and the high cost of investments for purchase of adequate equipments, this process can be recommended only for production of semi-industrial soap.

The above described process enable production of laundry and simple toilet soaps. To produce special soaps (high class toilet soap, transparent soaps, medical soaps, shaving soap etc.) the application of other soap making processes is necessary.

A.II.4 Control of saponification

To follow-up the execution of saponification and to control the quality of the soap produced, you can practice two simple methods:

- A sample of well soap should melt in water without turning it muddy;
- The presence of small drops of fat bodies indicates a shortage in alkaline, thus incomplete saponification;
- A well made improved soap shall present a light spicy taste due to the light surplus of alkaline necessary for a good preservation for rancidity

For the consumer a good soap should have the following qualities:

- Have a clear color, fast white;
- Be hard on touch;
- Produce quickly abundant and stable foam;
- Have a soft and good effect on the skin;
- Be able to conserve during a long period without loosing the above mentioned qualities.

Soaps produced from simple fats scarcely have all these qualities.

The saponification of fat mixtures gives the operator the advantage to be able to influence the qualities of the final product by choosing fats with complementary properties as component.

For this reason, the best soaps are produced in practice by saponification of fat mixtures different origins. So, if you want to produce a hard consistency soap, the INS Factor of the mixture should have a minimum value of around 110. You therefore can choose fat which soaps have different qualities as concerning foaming, cleaning property, action or effect on the skin.

The limitating element to the extent of such compositions is the availability of the appropriate fat on a considered geographic area. The availability of the fat according to their source in the 3 main ecological zones which characterize the developing countries is the following:

Equatorial zone	Humid tropical zone	Semi arid tropical zone
copra	peanut	peanut
fat (pork)	cotton	neem
palm	karitea(shea)	tallow (mutton, cow)
palmist	fat (pork)
	palm
	pourghere
	castor plant

In chapters C to G the technical details about preparation of improved soaps at family and small-scale level (cold or semi-hot process) and based on locally available fats are explained.