Soap-Making Manual Informative Summary

Overview:

This manual, written by E. G. Thomssen in 1922, provides a comprehensive overview of soap-making practices. It begins with an explanation of soap’s chemical composition and then delves into the essential raw materials used in the industry, including oils, fats, rosin, and alkalis.

The manual thoroughly explores the different methods of soap-making, such as full boiling, cold process, and carbonate saponification. It goes on to classify various types of soaps, from laundry soaps to toilet soaps and specialized soaps like floating, transparent, and medicinal soaps. The book also dedicates a chapter to glycerine recovery, discussing various methods like saponification with caustic alkali, the Twitchell process, and autoclave saponification. Finally, the manual concludes with a detailed description of analytical methods used to control the quality of raw materials, finished products, and byproducts.

Key Findings:

The text highlights the importance of choosing high-quality raw materials, particularly in regards to the free fatty acid content, which directly impacts glycerine yield.
The manual emphasizes the importance of proper manufacturing techniques, noting that an excess of alkali can lead to harshness in the finished product, and an excess of water can lead to cracking.
The manual explores the rising significance of hydrogenated oils as a more affordable alternative to traditional fats and oils, particularly for laundry soaps.
It also emphasizes the critical role of analytical methods in maintaining quality control and optimizing efficiency in all stages of soap production, including raw material selection, glycerine recovery, and finished product inspection.

Learning:

Saponification: This chemical process is the core of soap making, combining fats or oils with an alkali to produce soap and glycerine. The reader will learn about various saponification methods, including the full boiling, cold process, and carbonate saponification processes.
Types of Soaps: The manual provides a detailed classification of different soap types, including their key ingredients, manufacturing processes, and desired properties. The reader will learn about laundry soaps, toilet soaps, floating soaps, transparent soaps, medicinal soaps, and textile soaps.
Glycerine Recovery: The manual explains how glycerine is extracted as a valuable byproduct of soap making. The reader will learn about methods for separating glycerine from spent lye, the Twitchell process, autoclave saponification, and other methods for maximizing glycerine yield.
Analytical Methods: The reader will gain knowledge about various chemical tests used to control the quality of oils, fats, alkalis, soaps, and glycerine. They will learn about tests for free fatty acids, moisture content, titer, unsaponifiable matter, and more.

Historical Context:

The manual was written in 1922, a time when the soap industry was undergoing significant changes, driven by the rising costs of traditional fats and oils. The discovery of oil hardening, the development of the Twitchell process, and the increasing use of cheaper ingredients like rosin were all shaping the industry. The text reflects these developments and provides insight into the challenges and opportunities faced by soap manufacturers of the time.

Facts:

Soap is a salt of fatty acids. Soap is formed when fatty acids react with an alkali, forming a salt.
Sodium soaps are harder than potassium soaps. This difference in hardness is due to the different molecular weights of sodium and potassium.
The detergent properties of soap are due to hydrolytic dissociation. When soap is dissolved in water, it breaks down into other substances, including caustic alkali and the acid alkali salt of the fatty acids.
Cocoanut oil is readily saponified. This makes it an ideal ingredient for soaps that need to lather quickly.
Palm oil develops free fatty acid rapidly. This reduces its glycerine yield.
Olive oil is mainly used in white Castile soap. It produces a slimy lather and imparts a characteristic odor to soap.
Cottonseed oil is used for floating and laundry soaps. It is not suitable for toilet soaps as it can cause yellow spotting.
Rosin is a cheaper alternative to tallow. It adds to the cleaning properties of soap but can also impart a yellow color.
Naphthenic acids are a valuable soap material. They form soaps with high solvent power for mineral oils and emulsify readily.
Hardened oils are a more affordable alternative to tallow. They are increasingly used in laundry soaps and can improve the hardness and lathering power.
The amount of glycerine yield is dependent on the percentage of free fatty acid. The lower the free fatty acid content, the higher the glycerine yield.
The strength of lye is measured using a hydrometer. This instrument measures the density of the lye solution, which is directly related to its alkali concentration.
Hard water contains calcium and magnesium salts, which react with soap to form insoluble lime soaps. This reduces the soap’s effectiveness.
Sodium silicate is used as a filler and also to soften hard water. It binds with calcium and magnesium ions, effectively removing them from the water.
Salt is used for “salting out” soap. This means that the soap is precipitated from the lye solution by adding salt, which reduces its solubility.
The cold process is the simplest method of soap making. It involves directly mixing lye and oils at a lower temperature, but it can result in an excess of free fat or alkali.
Marine soaps are designed to lather with saltwater. They are often made with high proportions of cocoanut oil.
Soft soaps are made with potash lye. They are commonly used in the textile industry and for washing automobiles.
Soap powders offer a greater profit than household soap. They are often filled with cheaper ingredients like salt, soda ash, and crushed minerals.
Floating soaps are made by incorporating air into the soap. This makes the soap less dense and allows it to float on water.

Statistics:

A 500% yield can be obtained for cocoanut oil soap. This refers to the amount of water absorbed by the soap, which subsequently dries out upon exposure.
Palm oil should yield approximately 12% glycerine. However, due to its high free fatty acid content, soap makers typically do not attempt to recover glycerine from palm oil.
Hardened cottonseed oil soap is twelve times harder than ordinary cottonseed oil soap. This indicates the significant effect of hydrogenation on the hardness of soap.
The lye in the glycerine change of full-boiled soap should have an alkalinity of 0.5%. This is a crucial measure of the effectiveness of the saponification process.
Marine soaps contain 10% or less free soda ash. This is a standard requirement for this type of soap.
Soft soaps typically yield 225%-300% based on the weight of oil used. This reflects the higher molecular weight of potassium compared to sodium.
A soap with 50% fatty acid content should contain about 2% carbonate of potash. This is a common proportion in potash soaps.
A typical laundry soap containing 40% rosin uses approximately 8,400 pounds of rosin per 1,400-pound frame of soap. This illustrates the significant proportion of rosin used in laundry soaps.
Floating soap bases can be made with 30% cocoanut oil, 15% cottonseed oil, and 55% tallow. This shows the use of cheaper oils to reduce the cost of floating soap production.
The percentage of cocoanut oil in a toilet soap base can vary from 10% to 25%. This proportion impacts the lathering qualities of the soap.
Cheap toilet soaps can be loaded with as much as 30% starch. This cheapens the soap but can affect its appearance and lathering properties.
A typical “glued up” soap contains 50%-55% fatty acids. This illustrates the use of fillers to reduce the cost of this type of soap.
About 8%-10% filling solution is added per 100 pounds of soap for gluing up. This is a standard proportion used in this method.
A good shaving soap should contain a 3% excess of stearic acid. This ensures a thick, creamy lather.
A typical shaving cream formula uses 165 pounds of stearic acid per 26 pounds of cocoanut oil. This illustrates the significant role of stearic acid in shaving creams.
Pumice or sand soaps often contain 705 pounds of pumice per 378 pounds of soda lye. This represents a typical proportion used in this type of soap.
Liquid soaps usually contain about 20% fatty acids. This is a common concentration for liquid soaps.
The Twitchell process typically yields 85%-95% fatty acids. This signifies the efficiency of this method in splitting fats and oils.
The lime saponification in an autoclave requires 2%-4% of lime. This is a typical proportion used in this process.
The fermentative process for splitting fats can yield 80% in 24 hours and 85%-90% in 48 hours. This illustrates the speed of this method of saponification.

Terms:

Saponification: The process of converting fats or oils into soap and glycerine by reacting them with an alkali.
Hydrolytic Dissociation: The process of breaking down a compound by water into other substances.
Titer: The solidification point of the fatty acids in a fat or oil.
Unsaponifiable Matter: Substances in fats or oils that are not saponified by alkali and are soluble in fat solvents.
Nigre: The dark, viscous layer that settles to the bottom of the soap kettle during the boiling process.
Graining: The process of precipitating soap from the lye solution by adding salt.
Running: The process of continuously pumping soap from the skimmer pipe back into the top of the kettle to prevent settling and create a homogeneous mixture.
Figging: A crystalline-like formation that occurs in soft soaps due to the crystallization of stearine as the soap cools.
Curd Soap: A soap that is finished in a grained state.
Gluing Up: A method for cheapening soap by adding fillers to reduce the percentage of fatty acids.
Sulphonated Oil: A type of oil that has been treated with sulfuric acid to form a sulfonated compound, used in dyeing and printing textiles.

Examples:

Fuller’s Earth Bleaching: This process involves adding Fuller’s earth to melted tallow to remove impurities and improve its color. The mixture is then filtered through a heated press, leaving behind a clear, bleached oil.
Chrome Bleaching of Palm Oil: This method involves adding a mixture of sodium bichromate and hydrochloric acid to palm oil, which releases oxygen to bleach the oil. The process requires careful temperature control and settling.
Marine Soap Manufacture: This process involves saponifying cocoanut oil with strong lye (25°-35° B.) in an open kettle, preventing settling by continuously pumping the soap mixture.
Soft Soap for Textile Purposes: A mixture of red oil, house grease, caustic soda lye, and carbonate and hydroxide of potash is saponified in an open kettle, resulting in a soft soap used for washing and dyeing textiles.
Cold Made Cocoanut Oil Soap: This simple method involves mixing cocoanut oil with strong lye (35° B.) in a crutcher until the soap thickens and leaves an impression when a finger is drawn over its surface. The mixture is then poured into frames to solidify.
Settled Rosin Soap: This method involves boiling a mixture of fats (tallow, grease, cottonseed oil, etc.) with rosin and lye in an open kettle. The soap is then grained with salt, settled, and the lyes drained off for glycerine recovery. The remaining soap is strengthened with more lye and rosin, then settled again. The final soap is then pumped to a crutcher and filled with additional ingredients like sal soda and mineral oil.
Soap Powder Manufacture: Dry soap chips are mixed with fillers (soda ash, silica, etc.) and alkali in a specially-adapted mixer. The mixture is then crushed and pulverized and packed into containers.
Scouring Soap: A cocoanut oil soap base is mixed with silex (a type of silica) and hot water in a crutcher. The mixture is then poured into frames or molds to solidify.
Floating Soap: A soap base containing a high proportion of cocoanut oil is boiled in an open kettle. Air is then incorporated into the hot soap using a specialized crutcher, which causes the soap to float.
Transparent Soap: A mixture of tallow, cocoanut oil, castor oil, sugar, glycerine, soda lye, and alcohol is heated in a crutcher until dissolved. The mixture is then poured into frames to solidify, producing a transparent soap.

Conclusion:

This 1922 manual offers valuable insight into the soap-making processes of the time, highlighting the importance of selecting quality raw materials, employing accurate analytical methods, and keeping up with technological advances. The book emphasizes the need for careful manufacturing techniques to produce soaps with the desired properties, such as hardness, lathering power, and color. The manual also reflects the evolving landscape of the soap industry, with the emergence of hydrogenated oils and new saponification methods like the Twitchell process, showcasing the industry’s drive towards efficiency and cost-effectiveness. This historical perspective is essential for understanding the development of the soap industry and the continued relevance of its core principles.

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