ISAAC JOHNSON AND THE SECRET REVEALED
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Home > Isaac Johnson and the Secret Revealed
This is an exerpt from Innovations in Cement
Manufacturing, Chapter 1.
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| The Patent Portland Cement Works of Ed. Fewer
at Lagerdorf in Holstein. This factory was founded in 1862 by
English expatriates Edward Fewer and William Aspdin. |
In 1838, the young chemically educated Isaac Charles Johnson was
hired by John Bazley White to be works manager of his Swanscombe
cement factory in Kent. He had an early interest in the so-called
Patent Portland cement then being produced by Joseph Aspdin in Wakefield
and later by William Aspdin in Rotherhithe. Although Joseph Aspdin
had been granted a patent for his new cement composition, the actual
process was kept very much a trade secret. In fact,William Aspdin
related in 1852 that [Johnson 1911]:
The most unscrupulous means were resorted to in order to obtain
knowledge of Mr. Aspdin’s mode of manipulation. Men in his
manufactory were enticed away and workmen employed in his works
where ‘Patent Portland Cement’ was used were bribed
to spoil it. These and similar discreditable manoeuvres were continually
resorted to.
Indeed,William Aspdin, attempting to shield the process from any
potential competitors, actively promoted the mystery of portland
cement and its manufacture. In 1880, I. C. Johnson related in a
trade publication, “The Building News,” [Redgrave and
Spackman 1905] that about 1845 when young Aspdin began work at Rotherhithe
for Maude & Son, he himself was manager of the J. B. White &
Sons works at Swanscombe. At that time, the Swanscombe works produced
only Roman cement, Keene’s plaster, and Frost’s cement.
His employers were attracted by the promotion and claims being made
for this stronger and more durable portland cement, and negotiated
with Aspdin to join in its manufacture. However, no agreement could
be reached with William Aspdin. Johnson then stated that:
I advised my employers to leave the matter to me, fully believing
that I could work it out. As I before said, there were no sources
of information to assist me, for although Aspdin had works, there
was no possibility of finding out what he was doing, because the
place was closely built in, with walls some 20 feet high, and with
no way into the works, excepting through the office. I am free to
confess that if I could have got a clue in that direction I should
have taken advantage of such an opportunity, but as I have since
learned, and that from one of his later partners, that the process
was so mystified that anyone might get on the wrong scent –
for even the workmen know nothing, considering that the virtue consisted
in something Aspdin did with his own hands. Thus he had a kind of
tray with several compartments, and in these he had powdered sulphate
of copper, powdered limestone, and some other matters. When a layer
of washed and dried slurry and the coke had been put into the kiln,
he would go in and scatter some handfuls of these powders from time
to time as the loading proceeded, so the whole thing was surrounded
by mystery. What then did I do? I obtained some of the cement that
was in common use, and, although I had paid some attention to chemistry,
I would not trust myself to analyse it, but I took it to the most
celebrated analyst of that day in London, and spent some two days
with him. What do you think was the principal element, according
to him? Sixty percent of phosphate of lime! All right, thought I,
I have it now. I laid all the neighbouring butchers under contribution
for bones, calcined them in the open air, creating a terrible nuisance
by the smell, and made no end of mixtures with clay and other matters
contained in the analysis, in different proportions and burnt to
different degrees, and all without any good result.
Compared to Aspdin’s Patent Portland cement, Frost’s
British cement was clearly inferior. Frost’s cement, according
to Johnson, was composed of two parts chalk to one part of Medway
clay, was calcined lightly, and weighed only 32 to 36 kg per bushel.
However, Johnson was not about to admit defeat. His narration continued:
I had a laboratory and appliances on the premises, so I worked
night and day to find out the component parts of the stones from
Harwich and Sheppey. Having found these, and having tried many experiments,
spreading over some months, in putting different matters together,
I began to think that lime and alumina were the chief ingredients
necessary. I therefore tried quicklime powdered and mixed with clay
and calcined, by which means I got something nearer. It was a cement
very much like Frost’s. After this I used chalk and clay as
used in Frost’s cement, but with more chalk in proportion.
The resulting compound being highly burned, swelled, and cracked.
By mere accident, however, some of the burned stuff was clinkered,
and, as I thought, useless, for I had heard Colonel Pasley say that
he considered an artificial cement should feel quite warm after
gauging, on putting your hand on it, and that in his experiments
at Chatham he threw away all clinkers formed in the burning. However,
I pulverised some of the clinker and gauged it. It did not seem
as though it would harden at all, and no warmth was produced. I
then made mixtures of the powdered clinker, and powdered lightly-burned
stuff, this did set, and soon became hard. On examining some days
later the clinker only, I found it much harder than the mixture;
moreover, the colour was of a nice grey.
I went on making different mixtures until I came to 5 of chalk
and 2 of Medway clay, and this gave a result so satisfactory that
hundreds of tons of cement so mixed were soon afterwards made. Some
of this cement was sent to the French Government Works at Cherbourg,
as was, as I believe, set up as a standard of quality to which all
subsequent purveyors had to conform.
Isaac C. Johnson considered himself to be the inventor of “true”
portland cement. Up to the time of his death in 1911, at the age
of 100, he claimed that “the portland cement of Aspdin was
no more like the cement that is made today than chalk is like cheese!”
Although William Aspdin’s cement was partly clinkered, Johnson
was the first to recognize the critical importance of actual clinker
formation of a raw meal and the accurate proportioning of ingredients.
The cement industry’s transition from meso-portland cement
to a normal or modern portland cement is in large part due to Johnson’s
initial research and continuing efforts to manufacture portland
cement of uniform quality on a scientific and commercial basis.
Johnson left J. B.White & Sons after 14 years as works manager
and struck out on his own. His new firm, I. C. Johnson & Co.,
obtained the Aspdin, Ord & Co. works at Gateshead-on-Tyne in
1856, and later built another cement plant at Greenhithe-on-Thames
in Kent.
 Interested
in the remaining history of Portland cement manufacturing? Check
out PCA’s Innovations
in Cement Manufacturing SP400
(also available in a fully searchable CD-ROM format, CD400).
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