Excerpts from the Society's Transactions

This is an excerpt from the paper entitled "The Macintosh: the Paternity of an Invention" by H Schurer, published in the Transactions of the Newcomen Society, 1951-53 Vol 28.

Hancock's masticator

Many strands are woven into the invention of the 'macintosh' - the culmination of a long and complex development which resulted in the inventor's name being adopted as a new word in the English language.

In this paper, the author traces the seeds of development from the time preceding the discovery of America, to 1836 - the year of the famous lawsuit - in which Charles Macintosh's patent was described by the Attorney-General as being "almost as well known as Watt and Boulton's patent for steam engines or Arkwright's for spinning machines".

The oldest records tell of the utilisation of rubber in combination with textiles for waterproofing purposes: "rubber-coated rain capes were worn by the Indians of Escuintla on the Pacific coast of Guatemala, a region of heavy rainfall". Early records describe "an attendant wearing a rubber-coated poncho" and Aztec soldiers "clad in garments woven from the fibre of the henequen coated with indiarubber gum". Rubber was used in religious ball games, in magic practices, and in native surgery and medicine - all applications associated with native ways of thinking abhorrent to the Spanish Conquerors, and so the use of latex for waterproofing garments appears to have been the one and only application that the Conquerors adopted.

No progress was made with the introduction of the substance to Europe before the middle of the 18C and it is only with Francois Fresnau, who was the first to seize on the potential of the substance, that we enter the age of rubber science... He thought of the latex as a waterproofing agent, and he proposed this application as an article of everyday use in the Western world and not as a curiosity figuring in travellers' tales. (He used latex for waterproofing covers for his scientific instruments, and was the first to propose the use of turpentine as a solvent).

The extent to which the brilliant minds of the period were struck by the unusual properties of the substance caoutchouc is illustrated by the fact that a leading economist of the age, found time to devote a Mémoire to the "elastic resin" of French Guiana making forecasts of its wide range of possible applications and emphasising the advantages to be expected from rubber-textile combinations. This was in 1769. The turning point in the story is 1779, when the Italian scientist, Giovanni Fabbroni, was sent to Paris and London by the Grand Duke Leopold of Tuscany to purchase scientific instruments for his "cabinet" of physical chemical science (which became the Science Museum of Florence). Fabbroni, while in London mixed with leading scientists such as John Ingenhousz, Richard Kirwan, Joseph Priestley and Sir Joseph Banks, all of whom had shown interest in the newly discovered substance and in the properties of the "elastic gum"...

It was left to James Syme (1799-1870) a Scottish medical student to make the discovery of the cheap and efficient rubber solvent the lack of which had held up the rubber industry for so long. He found that coal-tar distillate was as good a solvent as mineral naphtha. He announced his discovery in 1818 and it was by a coincidence that in 1819 Charles Macintosh made his contract with the Glasgow gasworks for delivery of coal tar to his factory, for purposes quite different from rubber utilisation. Syme experimented with water-proofing garments, as we know from a later source, but he did not employ the sandwich construction. This two-ply principle was also developed independently in England, and secretly, a few year's before Macintosh's patent, with the important difference that turpentine was used.

Some years before Macintosh took out his patent, Thomas Hancock had invented the "masticator", the first machine specifically designed for the processing of rubber. This was a spiked cylinder rotating within a hollow casting thus creating ever newly-cut rubber surfaces, which emerge from the machine as a united plastic compound. The invention proved to be very important to Macintosh's process, but the secret of the masticator was betrayed by one of Hancock's workmen and Macintosh's patent was infringed. However, in the lawsuit of 1836 the Macintosh-Hancock firm came out triumphant. The process of early manufacture of the cloth in Macintosh's Glasgow works (and later in the Manchester factory) is descibed briefly in this paper:

At first operations were carried out by hand. The solution was put on the fabric by means of a brush, uneven parts were finished off with a spatula. First one fabric was proofed and then the other. The union of the two fabrics was effected by passing the fabric between a pair of rollers. To test the double-texture fabric, a piece of board was placed under the fabric, a little water was then put on the surface, the board was tapped with the hand, and if water came through the cloth was insuffuciently proofed...

There were also some interesting and unexpected early uses of rubber-coated textiles, other than for rainproofing garments:

A few years after Fabbrioni's discovery in 1779, a rubber solution was actually used to render a textile fabric impermeable to gas, and from the quarrels between distinguished men of science arising out of the invention of the hydrogen balloon, it is clear that a rubber solution was used for rendering the balloon cloth gas proof. When in 1836 Macintosh sued the firm of Everington & Ellis for the infringement of his patent, the rubber solution used by the early aeronauts to render balloon fabric gas-proof was discussed in great detail...

Another unusual early application foreshadows the two-ply construction on which Macintosh's "double texture cloaks" were based. Some Spanish scientists, settled in Mexico, actually succeeeded in inducing the Spanish Colonial Government to finance a series of experiments which were undertaken with a view of developing leak-proof containers for mercury, then shipped out on a large scale from Spain to Mexico.

Note: The macintosh is also commonly spelt 'mackintosh'.