Chemische Fabrik Kalk
Historic German chemicals and fertilizer producer based in Cologne-Kalk.
Last updated November 4, 2026
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Overview
Chemische Fabrik Kalk, commonly abbreviated CFK, was a German chemicals and fertilizer company established in 1858 in the then-independent village of Kalk, on the right bank of the Rhine opposite central Cologne. Julius Vorster, a merchant who had previously operated a chemical works, and Hermann Julius Grüneberg, a chemist and pharmacist, founded the business as Chemische Fabrik Vorster & Grüneberg, Cöln. The company began by industrializing the production of potassium nitrate, while generating sodium carbonate as a by-product. Potassium nitrate served food-preservation and black-powder applications, and the business grew rapidly during its first years. CFK’s early development combined chemical manufacturing with control of raw-material supplies. The founders obtained access to carnallite-bearing salt deposits near Staßfurt and developed methods for recovering potassium chloride. The company also entered sodium chloride, superphosphate, ammonium sulfate, magnesium sulfate, sulfuric acid, nitric acid and other industrial chemicals. During the second half of the nineteenth century it operated or invested in several production sites in the Rhineland and elsewhere, including ammonium-sulfate facilities and fertilizer operations. Its product range increasingly connected basic chemicals with agricultural inputs. The company experienced a financial setback in 1867 after an unsuccessful British investment and weaker demand. It recovered through product diversification, including magnesium sulfate, and through stronger markets for potassium nitrate. Carl Scheibler’s work in the fertilizer division helped establish Thomas phosphate as a relatively inexpensive agricultural fertilizer. In 1892 the business was reorganized as Chemische Fabrik Kalk GmbH, one of the early German companies formed under the newly introduced limited-liability company framework. Around the beginning of the twentieth century, potassium-carbonate production gave way to sodium carbonate made using the Solvay process, reflecting changing competitive conditions. By 1908 CFK manufactured a broad portfolio including ammonia compounds, sodium hydroxide, sodium sulfate, nitric acid, hydrochloric acid, sulfuric acid, sodium carbonate and several fertilizers. Its main works, together with associated sites and interests, represented a substantial industrial complex, and the factory employed more than 1,200 people. The tall chimney and water tower became defining features of the Cologne-Kalk skyline. During the First World War the company shifted toward saltpeter and other materials relevant to the wartime economy. It later operated an explosives research laboratory, but the Treaty of Versailles required the end of explosives production and closure of that laboratory. In the interwar period, fertilizer remained central to the business. CFK developed products using ammonium nitrate and calcium carbonate, and in 1930 introduced Scheibler’s Kampdünger, a two-component fertilizer based on lime, ammonium and phosphorus. Under the Nazi regime the company increasingly concentrated on materials connected with explosives production. During the Second World War it used approximately 460 forced laborers, initially from Poland and later from the Soviet Union. Allied bombing severely damaged the works: the sulfuric-acid plant was destroyed in 1943, and most production had stopped by 1944. The factory was closed in March 1945 after roughly 80 percent of its production facilities had been destroyed. Reconstruction began soon after the war. In August 1945 the works produced burnt lime for barter, followed by the resumption of ammonium-sulfate production in 1946 and the rebuilding of major facilities. Superphosphate and Kampdünger production restarted in 1948; the potash-containing version was marketed as KAMPKA-Dünger. By 1950 production had returned to its prewar level, and CFK held a significant share of the German sodium-carbonate market. Salzdetfurth AG acquired a minority interest in 1952, raised it to 75 percent in 1957 and bought the remaining shares in 1960. Under Salzdetfurth, the plant was modernized, including new phosphate capacity, a taller chimney and increasingly automated filling and loading operations. Nevertheless, the sodium-carbonate facilities became technologically dated, and the company struggled to develop products that could open new markets. Salzdetfurth was subsequently combined with other potash and mining interests, leading to the formation of Kali und Salz AG, the predecessor of today’s K+S group. CFK expanded into flower and garden fertilizers during the 1970s, but its Cologne site ultimately became uneconomic and difficult to expand in a densely populated urban district. All production facilities of the former Chemische Fabrik Kalk were closed in 1993. The site was demolished and decontaminated. Cologne police headquarters and the Köln Arcaden shopping mall were later developed on the former industrial premises. The Chemische Fabrik Kalk name survived only as the designation of a wholesale subsidiary within the K+S organization, rather than as an operating chemical factory. The brand therefore represents both a major chapter in Cologne’s industrial history and the transition from nineteenth-century integrated chemical works to modern specialized corporate groups.
History
Chemische Fabrik Kalk was founded on 1 November 1858 by Julius Vorster and Hermann Julius Grüneberg. The founders selected Kalk because it offered industrial land near Cologne and access to transport routes. Construction began on the site of a former iron foundry, and production started in February 1859. The original process converted potassium carbonate and sodium nitrate into potassium nitrate, with sodium carbonate recovered as a by-product. Output rose from 250 metric tons in 1859 to 2,400 metric tons in 1864, while the workforce expanded beyond the initial ten employees. The business soon integrated upstream resources and broadened its portfolio. It acquired salt-mining interests near Staßfurt, developed processes for recovering potassium chloride from carnallite and built related production capacity in the Staßfurt and Leopoldshall area. From 1860 it also produced sodium chloride. Superphosphate followed in 1864, ammonium sulfate in 1865 and potassium carbonate using the Leblanc process in 1866. The company established ammonium-sulfate facilities in several German cities and in Saint Petersburg, although many were later closed when gasworks retained or commercialized ammonia by-products. A difficult period in 1867 was addressed through diversification, especially magnesium sulfate and the recovery of potassium-nitrate markets. Fertilizer became increasingly important. Carl Scheibler introduced Thomas phosphate, an inexpensive fertilizer based on steelmaking slag, and later established Düngerfabrik C. Scheibler & Co. with participation from CFK’s owners. The Kalk site added sulfuric- and nitric-acid facilities in 1881. In 1892 the partnership was renamed Chemische Fabrik Kalk GmbH, shortly after German limited-liability legislation was introduced. After 1900 the company discontinued potassium-carbonate production in response to competition and concentrated on sodium carbonate made by the Solvay process. In 1908 its portfolio included ammonia compounds, caustic soda, sodium salts, mineral acids, soda ash and fertilizers. The company’s industrial footprint and employment made it one of Cologne’s important employers, while its water tower and chimney became prominent city landmarks. The First World War caused an initial reduction in employment and production, but the company later concentrated on saltpeter and established an explosives research laboratory. Postwar treaty restrictions ended that activity. During the 1920s CFK responded to rising raw-material costs with compound fertilizers, and in 1930 marketed Scheibler’s Kampdünger. From 1933 onward the company increasingly supplied materials associated with explosives production. It employed forced labor during the Second World War, including roughly 460 people from Poland and the Soviet Union. Bombing from 1942 onward destroyed much of the plant, and production ceased in March 1945. The works restarted with burnt-lime production in August 1945. Ammonium sulfate resumed in 1946, major reconstruction occurred in 1947, and superphosphate and Kampdünger returned in 1948. The potash-enriched product was sold as KAMPKA-Dünger. By 1950 the company had recovered its prewar output and had a notable position in Germany’s soda-ash market. Salzdetfurth AG progressively acquired CFK between 1952 and 1960. Modernization included phosphate capacity, a 120-meter chimney and automated packaging and loading systems. Salzdetfurth later became part of the corporate structure that formed Kali und Salz AG, the predecessor of K+S. CFK added flower and garden fertilizers in the 1970s, but aging production equipment, limited urban expansion space and inadequate access to new product markets weakened the Cologne operation. Production was finally closed in 1993. The factory was demolished after environmental decontamination, and the former industrial land was redeveloped for public and commercial uses. The CFK name survived only in wholesale activities associated with K+S.
- 1993
Cologne production ends
[1]All production facilities at the former factory site were closed.
- 1960
Acquired by Salzdetfurth AG
[1]Salzdetfurth AG acquired the remaining interest in CFK and took full ownership.
- 1948
Postwar fertilizer production resumes
[1]Superphosphate and Kampdünger production restarted during reconstruction.
- 1945
Factory closed after wartime damage
[1]The works stopped operations after approximately 80 percent of the production facilities had been destroyed.
- 1930
Scheibler’s Kampdünger launched
[1]The company introduced a compound fertilizer based on lime, ammonium and phosphorus.
- 1900
Shift to Solvay soda ash
[1]Potassium-carbonate production ended and sodium carbonate production using the Solvay process became central.
- 1892
Renamed Chemische Fabrik Kalk GmbH
[1]The partnership was converted into a limited-liability company and adopted the CFK name.
- 1864
Superphosphate introduced
[1]CFK began manufacturing superphosphate fertilizer from phosphorite.
- 1859
Production begins
[1]The new works began producing potassium nitrate and sodium carbonate by-product.
- 1858
Company founded in Kalk
[1]Julius Vorster and Hermann Julius Grüneberg founded Chemische Fabrik Vorster & Grüneberg, Cöln.
Products and positioning
Historically positioned as an integrated German producer of basic chemicals, mineral fertilizers and industrial salts, with a strong regional base in Cologne and later a role within the K+S potash and fertilizer group.
Industrial chemical · 1859
Potassium nitrate
The first major product of the Kalk works, potassium nitrate was initially made from potassium carbonate and sodium nitrate. It served food-preservation uses and was also an important ingredient in black powder. Production expanded substantially during the company’s first decade.
Basic chemical · 1859
Sodium carbonate
Sodium carbonate, or soda ash, was initially obtained as a by-product and later became a major commercial product. After 1900 CFK used the Solvay process, and the company became one of Germany’s significant soda-ash producers before its facilities ultimately became outdated.
Mineral fertilizer · 1865
Ammonium sulfate
CFK began producing ammonium sulfate in 1865 from ammonia and sulfuric acid. The company operated several related plants, and ammonium sulfate was among the products restarted during postwar reconstruction in 1946.
Mineral fertilizer · 1864
Superphosphate and Thomas phosphate
The company developed a substantial fertilizer business based on phosphate materials. Superphosphate production began in the 1860s, while Thomas phosphate, promoted by Carl Scheibler, offered a lower-cost fertilizer made from steelmaking slag and was aimed at broad agricultural use.
Compound fertilizer · 1930
Kampdünger and KAMPKA-Dünger
Scheibler’s Kampdünger, introduced in 1930, combined lime, ammonium and phosphorus components. After the war, a potash-containing version was marketed as KAMPKA-Dünger, with the name indicating the addition of potash salts. It became one of the company’s notable fertilizer products.
Industrial chemical · 1867
Magnesium sulfate
Introduced during the company’s nineteenth-century financial recovery, magnesium sulfate was especially intended for export to the United Kingdom, where it was used as a drying agent in textile applications.
Controversies
1940
Use of forced labor during the Second World War
During the Second World War, Chemische Fabrik Kalk used approximately 460 forced laborers, initially from Poland and later from the Soviet Union. The labor deployment formed part of the wartime operation of the factory under Nazi Germany.
Brand decisions
1993
Closure of the Cologne-Kalk worksStrategyBackground
The factory faced aging equipment, constrained expansion space in a densely populated district and difficulty entering new product markets.
Action taken
All production facilities at the former CFK site were shut down.
Aftermath
The site was demolished and decontaminated; the name continued only as a wholesale subsidiary within K+S.
1960
Full acquisition by Salzdetfurth AGM&ABackground
Salzdetfurth AG had acquired 25 percent of CFK in 1952 and raised its interest to 75 percent in 1957.
Action taken
Salzdetfurth AG acquired the remaining 25 percent and took full control.
Aftermath
The new owner modernized the facilities and later became part of the corporate lineage leading to K+S.
1945
Postwar reconstruction and restartStrategyBackground
Bombing had destroyed most production facilities and the factory had closed in March 1945.
Action taken
Workers repaired surviving equipment and restarted with burnt lime, followed by ammonium sulfate, superphosphate and fertilizer production.
Aftermath
By 1950 production had returned to its prewar level.
1930
Launch of Scheibler’s KampdüngerProduct launchBackground
Fertilizer demand was recovering, but raw-material price increases encouraged the use of by-products and blended formulations.
Action taken
The company introduced a two-component fertilizer based on ammonium nitrate and calcium carbonate, with lime, ammonium and phosphorus components.
Aftermath
The product was readily accepted by the market and remained part of the postwar product family as KAMPKA-Dünger.
1900
Move from potassium carbonate to soda ashStrategyBackground
Competitive pressure made the earlier potassium-carbonate business less attractive.
Action taken
CFK ceased potassium-carbonate production and expanded sodium-carbonate production using the Solvay process.
Aftermath
Soda ash became one of the company’s principal products during the twentieth century.
1892
Conversion into Chemische Fabrik Kalk GmbHStrategyBackground
The original partnership had operated for more than three decades and Germany had newly introduced the limited-liability company form.
Action taken
The business was renamed Chemische Fabrik Kalk GmbH and reorganized as a GmbH.
Aftermath
The CFK name became the company’s enduring corporate identity.
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