Now! Then! Joseph Aspdin, bricklayer of Hunslet (Leeds), submits the process description for his patent for “artificial stone,” which he calls “Portland cement”

15 December 1824: Joseph Aspdin, bricklayer of Hunslet (Leeds), submits the process description for his patent for “artificial stone,” which he calls “Portland cement”

HMG. 1824. Artificial Stone. London: HMG. Get it:

Excerpt

My method of making a cement or artificial stone for stuccoing buildings, waterworks, cisterns, or any other purpose to which it may be applicable (and which I call Portland cement) is as follows: I take a specific quantity of limestone, such as that generally used for making or repairing roads, and I take it from the roads after it is reduced to a puddle or powder; but if I cannot procure a sufficient quantity of the above from the roads, I obtain the limestone itself, and I cause the puddle or powder, or the limestone, as the case may be, to be calcined. I then take a specific quantity of argillaceous earth or clay, and mix them with water to a state approaching impalpability, either by manual labour or machinery. After this proceeding I put the above mixture into a slip pan for evaporation, either by heat of the sun or by submitting it to the action of fire or steam conveyed in flues or pipe under or near the pan till the water is entirely evaporated. Then I break the said mixture into suitable lumps and calcine them in a furnace similar to a lime kiln till the carbonic acid is entirely expelled. The mixture so calcined is to be ground, beat, or rolled to a fine powder, and is then in a fit state for making cement or artificial stone. This powder is to be mixed with a sufficient quantity of water to bring it into the consistency of mortar, and thus applied to the purposes wanted.

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To facilitate reading, the spelling and punctuation of elderly excerpts have generally been modernised, and distracting excision scars concealed. My selections, translations, and editions are copyright.
Abbreviations:

ER: East Riding
GM: Greater Manchester
NR: North Riding
NY: North Yorkshire
SY: South Yorkshire
WR: West Riding
WY: West Yorkshire

Comment

Wikipedia points out that this is not today’s Portland cement:

Aspdin called the product Portland cement because set mortar made from it resembled “the best Portland stone”. Portland stone was the most prestigious building stone in use in England at the time. The patent clearly does not describe the product recognised as Portland cement today. The product was aimed at the market for stuccos and architectural pre-cast mouldings, for which a fast-setting, low-strength cement was required (see cement). It was fired at low temperature (below 1250°C) and therefore contained no alite (Ca3SiO5, tricalcium silicate).

The product belongs to the category of “artificial cements” that were developed to compete with Parker’s Roman cement, and was similar to that developed much earlier by James Frost. The process described is a “double burning” process in which the limestone is burned on its own first, then slaked, mixed with clay, and burned again. This was a common practice for manufacturers of both Artificial and Portland cements when only hard limestones were available. The grinding technology of the time consisted only of flat millstones, and it was more economic to comminute the limestone by burning and slaking than by grinding.

The limestone he used was the Pennines Carboniferous limestone of the area, which was used for paving in the towns and on the turnpike roads. The characteristic practise of the patent (and of his lime patent) is the use of “road sweepings” as a raw material. He says that if the sweepings are not available he obtains ‘the limestone itself”. It is significant that Joseph Aspdin was twice prosecuted for digging up whole paving blocks from the local roads. Limestone supply was clearly a major headache for Aspdin in the days before stone could be brought in by rail.

His son William’s innovation was to make a mix with a higher limestone content, to burn it at a higher temperature using more fuel, and to grind the hitherto-discarded hard clinkered material, hence increasing wear-and-tear in the grinding process. However, William did not file for a patent on his modified process, and sometimes claimed his father’s patent.[4] In 1848, William moved south to Northfleet, in Kent, where inexhaustible supplies of soft chalk were available.[6] A history of “financial missteps” and questionable business arrangements suggests that William may have been both inept and dishonest. Nonetheless, he is credited with launching the “modern” Portland cement industry.[4]

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Original

A.D. 1824 … Nº 5022
Artificial Stone.
ASPDIN’S SPECIFICATION

TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH ASPDIN, of Leeds, in the County of York, Bricklayer, send greeting.

WHEREAS His present most Excellent Majesty King George the Fourth, by His Letters Patent under the Great Seal of the United Kingdom of Great Britain and Ireland, bearing date at Westminster, the Twenty-first day of October, in the fifth year of His reign, did, for Himself, His heirs and successors, give and grant unto me, the said Joseph Aspdin, His especial licence, that I, the said Joseph Aspdin, my executors, administrators, and assigns, or such others as I, the said Joseph Aspdin, my executors, administrators, and assigns, should at any time agree with, and no others, from time to time at all times during the term of years therein expressed, should and lawfully might make, use, exercise, and vend, within England, Wales and the Town of Berwick-upon-Tweed, my invention of “AN IMPROVEMENT IN THE MODES OF PRODUCING AN ARTIFICIAL STONE;” in which said Letters Patent there is contained a proviso obliging me, the said Joseph Aspdin, by an instrument in writing under my hand and seal, particularly to describe and ascertain the nature of my said Invention, and in what manner the same is to be performed, and to cause the same to be inrolled in his Majesty’s High Court of Chancery within two calendar months next and immediately after the date of the said part recited Letters Patent (as in and by the same), reference being thereunto had, will more fully and at large appear.

NOW KNOW YE, that in compliance with the said proviso, I, the said Joseph Aspdin, do hereby declare the nature of my said Invention, and the manner in which the same is to be performed, are particularly described and ascertained in the following description thereof (that is to say):-

My method of making a cement or artificial stone for stuccoing buildings, waterworks, cisterns, or any other purpose to which it may be applicable (and which I call Portland cement) is as follows:- I take a specific quantity of limestone, such as that generally used for making or repairing roads, and I take it from the roads after it is reduced to a puddle or powder; but if I cannot procure a sufficient quantity of the above from the roads, I obtain the limestone itself, and I cause the puddle or powder, or the limestone, as the case may be, to be calcined. I then take a specific quantity of argillacious earth or clay, and mix them with water to a state approaching impalpability, either by manual labour or machinery. After this proceeding I put the above mixture into a slip pan for evaporation, either by heat of the sun or by submitting it to the action of fire or steam conveyed in flues or pipe under or near the pan till the water is entirely evaporated. Then I break the said mixture into suitable lumps and calcine them in a furnace similar to a lime kiln till the carbonic acid is entirely expelled. The mixture so calcined is to be ground, beat, or rolled to a fine powder, and is then in a fit state for making cement or artificial stone. This powder is to be mixed with a sufficient quantity of water to bring it into the consistency of mortar, and thus applied to the purposes wanted.

In witness whereof, I, the said Joseph Aspdin, have hereunto set my hand and seal, this Fifteenth day of December, in the year of our Lord One thousand eight hundred and twenty-four.

JOSEPH (L.S.) ASPDIN.

AND BE IT REMEMBERED, that on the Fifteenth day of December, in the year of our Lord 1824, the aforesaid Joseph Aspdin came before our said Lord the King in His Chancery, and acknowledged the Specification aforesaid, and all and every thing therein contained and specified, in form above written. And also the Specification aforesaid was stamped according to the tenor of the Statute made for that purpose.

Inrolled the Eighteenth day of December, in the year of our Lord One thousand eight hundred and twenty-four.

717 words.