The Sugar Mill Origins And Evolution Part 6: The Man of Steel

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Sugarcane (Saccharum officinarum) is a perennial grass of the family Poaceae. It is primarily cultivated for its juice, from which alcohol (through fermentation and distillation) and sugar (through dehydration and refining) can be obtained. Most of the world’s sugarcane is grown in subtropical and tropical areas.

It is commonly accepted today that sugarcane originated in Papua, New Guinea, where it was initially domesticated. The plant was then taken to other lands by traders, where its sweet virtues quickly made it a sought-after commodity.

It is also commonly accepted that around 10,000 years ago, the original inhabitants of Papua did not have tools to process the cane, meaning that they likely chewed it raw to extract the juice, which was consumed as- is (Noël Deerr, The History of Sugar: Volume One).

Not much written history exists that documents the early extraction of the juice for the purpose of dehydration and formation of sugar crystals until the publication of De Materia Medica, a pharmacopoeia of medicinal plants and the medicines that can be obtained from them, which was written between the years 50 and 70 of the current era by Pedanius Dioscorides, a Greek physician in the Roman army. This is the oldest record documenting the existence of crystalized sugar, which was used at the time to “treat indigestion and stomach ailments.”

How did people manage to extract the dissolved sugar from the juice? The answers to this question are at the core of this series. so join us, as we explore this fascinating topic!

                   The Sugar Mill Origins And Evolution

                           Part 6: The Man of Steel

In Part 5 we discussed the introduction of wind power as an alternative to animal or human force, to turn the vertical rollers crushing the cane.  As you recall, most of the moving parts of these mills were constructed of wood, which is not the sturdiest material.  Wood fibers have intrinsic flexibility, which allows wooden structures to bend and absorb some degree of pressure without breaking.  When crushing sugarcane, however, this flexibility leads to reduced pressure being applied to the cane itself, thus making the juice extraction process less efficient.

What the industry needed at that time was a sugarcane mill constructed of steel, but the steel manufacturing technology back then was still in its infancy and steel parts where extremely expensive to produce.  This is when our hero, Henry Bessemer, comes into the picture.

Bessemer was the son of an engineer and type-founder. He showed his considerable mechanical skill and inventive powers at an early age. After his invention of adjustable mechanical stamps for dating deeds and other government documents and his improvement of a typesetting machine, he went to the manufacture of “gold” powder from brass for use in paints.   

During Bessemer’s time there were only two iron-based construction materials: cast iron made by the treatment of iron ore with coke in the blast furnace and wrought iron made from cast iron in primitive furnaces by the laborious manual process of “puddling” (stirring the melted iron to remove carbon and raking off the slag).  

During the Crimean War, Bessemer invented an elongated artillery shell that was rotated by the powder gases. The French authorities with whom he was negotiating, however, pointed out that their cast-iron cannons were not strong enough for this kind of shell. He thereupon attempted to produce a stronger cast iron. In his experiments he discovered that the excess oxygen in the hot gases of his furnace appeared to have removed the carbon from the iron “pigs” that were being preheated—much as the carbon is removed in a puddling furnace—leaving a skin of pure iron. Bessemer then found that blowing air through melted cast iron not only purified the iron but also heated it further, allowing the purified iron to be easily poured. This heating effect is caused by the reaction of oxygen with the carbon and silicon in the iron. Using these new techniques (which later became known as the Bessemer Process), he was soon able to produce large, slag-free ingots as workable as any wrought-iron bloom, but far larger.  He also invented the tilting converter into which molten pig iron could be poured before air was blown in from below (source: Encyclopedia Britannica). 

In 1849, Bessemer met a Jamaican sugarcane planter, who described to him the juice extraction methods currently in use.  Bessemer was shocked to learn about the “wasteful” and “primitive” approach that was the norm those days.  Coincidentally, shortly after his meeting with the sugarcane planter, the Society of Arts and His Royal Highness Prince Albert announced the awarding of a gold medal to the person who could improve the sugarcane extraction process the most.  Bessemer had never seen sugarcane before, nevertheless he set on a quest to design and develop a sugarcane crusher.  To test his invention, he obtained sugarcane from Madeira, this was the first time he had held sugarcane in his hands.

His steam-operated invention, which he named the Plunger Mill, consisted of two pressing cylinders with draining holes along their sides.  Above the pressing tubes, Bessemer placed a hopper that would hold the sugarcane stalks vertically.  As the stalks fell (by gravity) into the cylinders, a plunger would cut the cane into 6 inch lengths on the forward stroke, pressing those sections of cane at the bottom of the cylinder.  On the return stroke, the plunger would cut additional cane pieces and would crush them at the top of the cylinder.  This application of continuous pressure meant that the bagasse (the sugarcane fibers) could not re-absorb the extracted juice.This new press was able to extract six hundred gallons of juice per hour, roughly 20 percent more than the average wooden roller mill, from the same quantity of sugarcane.  The Society of Arts was so impressed by his invention, that it awarded Bessemer with the gold medal.  Despite this recognition, however, this invention never became an industry standard.