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Editor’s note: This article is featured in the Fall 2009 issue of SDL Atlas Update, the company’s quarterly newsletter. To sign-up to receive the newsletter, send us an e-mail at firstname.lastname@example.org.
Manufacturers of textile dyes, apparel manufacturers, and retailers (often through third-party laboratories) routinely test the colorfastness of textiles to perspiration by use of either AATCC Test Method 15 or ISO 105-E04. AATCC Executive Vice President Jack Daniels recently wrote about this simple but very important test used globally for quality control and research:
AATCC began developing what has now become AATCC Test Method 15 Colorfastness to Perspiration, in 1949, and that method has been revised many times, particularly in the 1950s and 1960s. When ISO Technical Committee 38, Textiles was developed in 1947 a subcommittee was established to derive an ISO method based on the work of the Americans, through AATCC, the British, through the work of the Society of Dyers and Colourists (SDC) and including work being done on the European continent through the ECE. At that time the work through ECE appeared to be lead by the Germans and Swiss.
A very good account of the early history of colorfastness to perspiration may be found in an article by B. A. McSwiney, Professor of Physiology, at Leeds University, in the June 1929 issue of the Journal of the Society of Dyers and Colourists on Physiology and Industry. Work was being done on this subject in a number of countries, as color changes and staining were being observed that were differing from simply treating textile materials in dilute acidic solutions that had been proposed as early as 1905 by Cain and Thorpe. They had reported that fastness to perspiration is analogous to fastness to acids. In that early work, acetic and sulfuric acids were used. A very detailed chemical analysis of human perspiration was again reported by McSwiney and C. C. N. Vass in the June 1930 issue of the Journal of the Society of Dyers and Colourists. In McSwiney’s initial article, he mentioned that the American “Commission” had determined that freshly secreted perspiration contains 1-1.5% solids, 50% sodium chloride; 10% other inorganic constituents, such as phosphates, sulfates, and chlorides of magnesium, calcium, and potassium; 30% nitrogenous matter, chiefly urea; and 10% of organic acids, chiefly lactic acid, with possibly a little acetic acid.
The initial artificial perspiration solutions investigated by the various research groups incorporated varying amounts of sodium chloride, lactic acid, and disodium hydrogen phosphate for acidic solutions and sodium chloride, ammonium carbonate or ammonium hydroxide, and disodium hydrogen phosphate for alkaline solutions. Early work had reported that human perspiration varies between males and females and varies when people are under stress through fear or sports. For instance, females and the obese typically have higher glucose levels in their perspiration. It was reported that human perspiration is always slightly acidic, pH 5.1 to 6.77. On standing, however, it was found that perspiration can become alkaline through the decomposition of urea and other nitrogenous compounds which are present, converting into ammonia or ammonium carbonate. It was found that an increase in temperature speeds this conversion, and later it was determined that bacteria on the skin or in the perspiration can act as an accelerant. Typically the alkaline perspiration solutions were found to produce much more severe shade change and staining than the acid solutions, but there were a few exceptions.
In the early 1950s work was being done to assess colorfastness to perspiration on copper-complex and copper after-treated direct dyes which were popular in those days for dyeing cotton and wool, which were producing poorer results in actual wear than the artificial perspiration solutions up to that time were predicting. It was found that the copper atoms were being sequestered in certain direct dyes causing sever shade change, and if these same tested samples were retreated with copper salts, a restoration of the shade occurred. Of the many amino acids found in perspiration, histidine was by far the most active, and therefore the British, Americans, Germans, and Swiss began investigating the inclusion of various amounts of histidine hydrochlorides. The British wanted to include as much as 5.0 grams per liter, but the Americans had found that amount to produce far too severe results and would result in significant shade change in dyes that had previously be classified as being fair-to-good performers. The Americans began work using 0.25 grams of histidine monohydrochloride per liter in the acid perspiration solution and the Germans agreed with the Americans on this amount. The Swiss ignored the acid solutions and began incorporating 0.5 grams per liter histidine monohydrochloride in the alkaline their perspiration solution.
After the above groups began studying the inclusion of varying amounts of histidine monohydrochloride in artificial perspiration solutions, the Canadians became involved. They began looking at the general methods of application of the solutions, the influence of wet pickup and various staining fabrics. The Americans developed the Perspirometer, and later asked the Atlas Electric Devices Company (now SDL Atlas) to manufacture what became the simpler AATCC Perspiration Tester, designed by a Canadian, Carl Tiechgraber, who became involved with AATCC, as the Canadian work declined.
In 1974 the AATCC began listing only the acid perspiration solution, but continues to reference the alkaline solution, and articles that appeared in the October and November 1974 issues of Textile Chemist and Colorist provide good background information and laboratory versus wear trial data.
As of this time, AATCC continues to incorporate 0.25 grams per liter of L-histidine monohydrochloride in its acid perspiration solution. ISO 105-E04 currently specifies 0.5 grams per liter L-histidine monohydrochloride, so the AATCC and ISO methods are related, but not identical. Obviously, AATCC believes its method to provide the best representation of end-use performance. The ISO method continues to provide an alkaline perspiration solution that AATCC does not believe predicts normal end-use performance, as being much too severe.
Daniels wrote that he does not have an answer as to why the different sodium phosphates may be employed in these various methods, but suspects it had to do with chemicals that were readily available in the various laboratories around the world doing the early exploratory work.
From the articles mentioned, the researchers realized they needed these types of compounds to produce artificial perspiration solutions that would contain phosphates as found in human perspiration and that would yield solutions having specific pH ranges.
We hope you find the above information useful. Over the years there have been many researchers studying colorfastness to perspiration, and it is interesting that this activity became one of the very first projects undertaken by ISO/TC38/SC1-Tests for Coloured Textiles and Colorants.