Isis Logo Isis Brand.


  • Grid reference: SD7499543610
  • x=374995
  • y=443610
  • 53°53'15"N; 2°22'50"W
  • Civil Parish: Clitheroe, Lancashire

Clinker manufacture operational: 1894-1929

Approximate total clinker production: 340,000 tonnes

Raw materials: Carboniferous Limestone (Chatburn Limestone Formation: 348-352 Ma), with varying amounts of intercalated shale from quarry at 375300,443700.

Ownership: Isis Portland Cement Co. Ltd

This was a dry process plant designed and owned by Charles Spackman. There were originally six kilns (200 t/week) with Spackman’s drying chamber modification. A Schneider kiln (100 t/week, 5.0 MJ/kg) was installed in 1912 (see article), and a further one was added in 1919, the two being uprated to 150 t/week each by forced draught. The bottle kilns were then used as driers. The Bolton and Clitheroe railway dates from as early as 1850, and much of the product of the lime plants of Clitheroe and points further up the valley was shipped out by rail. The cement plants used it similarly to establish firm control of markets in north Lancashire. Spackman was not interested in up-rating or installing rotary kilns (which he rightly regarded as inefficient). The plant was very simple and could probably be operated by a workforce of ten or less, so it remained profitable enough. The plant continued in its small way until closure in 1929: the company was liquidated on 3 February 1930. The site was subsequently occupied by Ribblesdale plant, plans for the latter beginning as soon as this premium site came on the market. There appears to be no trace of the plant, expansion of Ribblesdale having re-worked the entire site.

No rotary kilns were installed.

Sources: Jackson, pp 252, 283, 294: Peter del Strother, History of Ribblesdale Cement, Castle Cement Ltd, 2008, ISBN 978-0-9545416-1-3, pp 22, 32, 33: Clitheroe Advertiser, 2 Aug 1912. Read the newspaper article.

The following is a transcript of an anonymous article that appeared in the Clitheroe Advertiser, 2/8/1912, kindly supplied to me by Peter del Strother.

It is the result of an organised visit of the local populace to the Isis plant, around the time of the installation of the first Schneider kiln.

The clay as brought in is slightly roasted (Note 1) in heaps under large sheds, each heap when finished representing one month's production. The stone is delivered into the works in wagons containing about ten tons, the contents of each are sampled, and the carbonate of lime determined before unloading. The clay is free from lime, consequently the composition of the stone being known a simple calculation gives the proportion of each material. The mixture is by weight and is finely crushed in a swing jaw crusher and elevated to hoppers above the grinding mills. The grinding is in two stages. In the first, a somewhat coarse gritty powder is obtained by grinding between burr stones. This is finished by tube mill to such a fineness that less than five percent of residue is left upon a sieve having 40,000 meshes to the square inch (Note 2). At this stage the composition of the mix is checked, the percentage of carbonate of lime being determined in samples taken at intervals. By the method employed a determination, accurate to with one half of one percent, can be made in seven minutes. The raw meal or flour as is it technically called is received into a series of tall receptacles or silos which not only serve as storage, but also as mixers. By means of extracting worms a constant stream of previously ground material is drawn out and is returned with the stream coming from the mills, while the other worms are employed to extract that required for the next step of the process (Note 3). The material extracted is collected into one conveyor at the delivery end of which it is mixed with about ten percent water. The damp mixture is conveyed to a floor above the presses, and by these it is formed into bricks which are passed directly to the kilns, of which two types are at present in use. An older one which works intermittently, and for which a portion of the succeeding charge is dried in chambers (Note 4) by heated air obtained during the burning of the preceding one, and one shaft kiln just set to work (Note 5). This works continuously, bricks as taken from the presses and coke being continually charged at the top, while clinker is drawn below. The kiln itself is constructed of steel plates lined with fire bricks and it works with natural draught, special arrangements having been made to ensure sufficient air supply, and consequently rapid burning and cooling of the charge. The charging floor is carried on an enclosing structure built up of broad flange beams, which also supports the chimney quite independent of the kiln. This is lined with specially made thin fire bricks built in cement and the plates are bolted (?) together. A scaffold formed of light (?) quartering was carried up with each belt of plates and firmly clasped to them. This at once served for lifting and bolting the plates and for putting in the lining. This type of kiln is repeated with some slight modifications. The whole is driven by a Pollit and Wigzell compound condensing engine of 450HP. The lighting is by arc lamps, power for these being obtained from a separate engine. An inspection of the laboratory bought the visit to an end.

Vote of thanks from Mr Platt of Salford to Mr Spackman of Isis:- "it was part of his duty to test cement for the large Corporation of Salford and in testing cement he had a pleasant experience a few years ago. Two samples of Portland cement were sent to him, one being highly priced and one being much cheaper. The price of the latter was so low indeed that the Committee who had advertised for contracts were very doubtful about it. The Committee sent samples to him and he did not know where either of them came from. The samples were both tested in the same way and the cheaper cement fulfilled the standard to a greater extent than the cement of a higher price. He afterwards found out that the cheaper cement was manufactured by the Isis Portland Cement company, of which Mr Spackman was the head."


Note 1. Meaning, it was dried.

Note 2. This sieve is around 75 μm, and this is a very fine grind.

Note 3. Thus, multiple storage bins are used, and the material is continually recirculated around them. This was about as good a blending system for dry meal as was available at the time.

Note 4. The Spackman chamber was on the same lines as the Johnson chamber, but adapted for drying and pre-heating stacked bricks rather than slurry. Spackman developed it during his time at the Barrow plant, and subsequently introduced it at several other locations.

Note 5. A second Schneider kiln was added after the war, and the bottle kilns were no longer used.