Soap (1948)

Carl Mason is planning a class demonstration of soap making to make the soap Carl uses fat and Li first he weighs out the LI or sodium hydroxide as it is usually called in a laboratory since the sodium hydroxide must be in solution to make soap Carl pours the solid sodium hydroxide into water when they are mixed heat develops so Carl sets the solution aside to cool while he adjusts the balance to weigh out the fat needed he uses about seven times as much fat as he does sodium hydroxide this is clean waste kitchen fat that Carl collected at home it should make good soap the fat must be warmed before mixing the sodium hydroxide with it a mix fix ing temperature of about 100° F gives good results the flame quickly warms the fat then Carl begins to add the sodium hydroxide it is the reaction between sodium hydroxide and fat form soap what is the nature of this reaction let's consider this a molecule of fat consisting of a glycerin part and an acid part and let's consider these molecules of lie consisting of sodium parts and hydroxide parts now when these molecules interact the sodium parts of the LI molecules go with the acid part of the fat molecule and the hydroxide parts of the LI molecule go with the glycerin part of the fat molecule this reaction results in three molecules of soap and one molecule of Glycerin fat plus Li gives soap plus glycerin this process is called saponification saponification is what occurs when fat and lie react in commercial soap making the glycerin is usually removed in about 10 minutes or as soon as the mixture of sodium hydroxide and fat has a honey-like texture it is ready to pour into a mold this mixture should stand several days more before it is used so that all of the fat and lie will react to form soap and glycerin Carl's soap has been standing for more than a week and he thinks it is ready to use it has a fine texture and should have good cleansing qualities but before Carl tries out his soap to see how well it will remove dirt let's take a close look at hands we say are dirty in a close view the skin would look something like this notice the oil film on the skin and the dirt particles suspended in it seen even closer it would look something like this the oil and the dirt particles coat the skin now when we use soap and water to wash our hands what happens for one thing the oil film breaks up into small globules that is it emulsifies and a layer of soap one molecule thick coats the skin the oil globules and the dirt particles closer still it would look like this the soap molecules not only free the oil and dirt from the skin but help keep them from becoming attached again if they touch a clean spot as the washing continues the soap films are indifferent to each other and so the oil globules and dirt particles can easily be rinsed off notice that oil globules or dirt particles that drop toward the skin during washing do not become attached again thus through washing and rinsing oil and dirt particles are cleaned away but a layer of soap molecules invisible to the eye remains on our hands even after rinsing now we will see soap making on a commercial scale this is the receiving yard of a large soap making plant here fats and oils arrive in carload Lots this man collects a sample from a tank car that has just come into the yard the sample he takes will be tested to make sure it is of good quality after testing the fat and oil in the tank car are pumped to the refinery here pipes lead the fattened oil to huge kettles the refinery man opens a valve and the oily mixture pours into the kettle here it is heated with a solution that removes acid impurities in a few hours when the impurities have settled out the refined oil mixed with bleaching substances goes to the filter press room these filters separate out the bleaching substances that have removed colored impurities from the oil a press man collects a sample of the fine clean bleached oil if the color appears satisfactory at this stage and after further tests the bleached oil will be pumped to the soapery to be used for soap making this oil serves the same purpose as the fat Carl Mason used in in his laboratory demonstration in this room called the soy refined and bleached oils that have passed required tests are mixed with lie and heated to make soap this soap maker checks the mixtures in the kettles in this Kettle the operation of saponifying and purifying the soap has been going on for nearly a week this reaction is the same as in the laboratory demonstration the soap maker now makes tests to see whether saponification is complete the feel of the mixture indicates whether there is any fat that is not reacted the taste indicates whether any Li remains this soap seems just right so the soap maker collects a sample for a more accurate check in the chemical Laboratory soap that passes all these tips goes to the drying room the soap still in liquid form first falls into a trough and on to a huge revolving roller the roller carries off a continuous thin layer of the liquid soap the soap layer cools on the roller and falls in clean white ribbons a conveyor belt carries the ribbons of soap into a drying oven after drying the soap travels onto this Hopper from the hopper a measured batch of soap falls into the mixer the mixer operator opens the safety guards to pour in preservatives perfumes and other Mater material needed in soap making he adds these ingredients to give special qualities to the soap in a few minutes the mixing is completed then the soap drops onto this revolving screw that feeds it into the bar forming machine the soap leaves the bar forming machine in one continuous bar a knife cuts the soap into sections then fine wires cut the sections into individual cakes a moving rack carries the cake to an inspector's table the inspector places the cakes on an endless belt the soap is now ready for Staffing and WRA cing and to start on its way to our home