Cause of Yellow Spots on Canvas Painted with Chrome Greens ANDREWJ. SNYDER,Kentucky Color & Chemical Company, Louisville, KY.
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N RECENT years the use of paint for making stripes and other patterns on cotton duck for use in the fabrication of awning and porch furniture has become quite general. This paper deals with the performance of chrome green when made into a suitable paint and used on the cotton duck. It deals in particular with the appearance of yellow spots which may develop on the chrome green pattern. Those yellow spots which vary in size, shape, degree of yellowing, and location on the stripe have occurred in widely separated parts of the country. The following are some of the reasons heretofore advanced as to the possible cause of the trouble: (1) bird droppings, which are often decidedly alkaline; (2) reducing compounds that might be present on the fabric; (3) metallic stains of iron or copper; (4)presence of alkali dust from sources such as cement, macadam roads, washing powders, soaps, etc., on the green. These may be the source of the trouble in a limited number of cases, but their presence can usually be determined by examining the spots microscopically. The general appearance of the yellow spots still pointed to the idea that the green had been acted upon by an alkali. If this was true, where did the alkali come from?
ALKALIFROM BACTERIA
were badly yellowed, and there was no evidence of the mold prowth on the duck. The author has established the fact that amine- or ammonia-forming bacteria are the cause of the trouble. The amines and ammonia produced by the bacteria are very soluble in water. These alkalies collect and concentrate in pockets and folds of the wet awning or other canvas product. If the canvas has been painted with chrome green, it is probable that a yellow discoloration will appear in a short time, if the conditions are suitable for bacterial growth, because of the destructive action of the free alkali. The amount of damage naturally depends upon the strength of the alkali that is produced, the length of time the alkali is in contact with the color, and a number of other factors. It is impossible to tell exactly when the cotton duck is infected by the bacteria, but the infection probably originates in spinning and weaving r o o m where molds and mildews are known to be prevalent. Most of them are spore formers, and are very resistant to heat and chemical reagents. The bacteria and spores do not cause any trouble unless these conditions-food, warmth, and moisture-favorable for their growth are present.
FOOD SOURCEOF BACTERIA
Having determined that bacteria were the cause of the A study of the problem starts with the fact that chrome trouble, it was necessary to h d their source of food. Since green is made by mixing lead chromate and ferriferrocyanide, Prussian blue is a nitrogen compound, there was a possibility generally known as Prussian blue. that the bacteria derived their nitrogen from the blue. This I n searching the literature as to the possible causes of the was easily determined by culturing pieces of the unpainted trouble, the author found numerous references stating that duck in the Petri dishes. These unpainted pieces develop cotton goods were susceptible to mildew. These references the alkaline reactions and odors more rapidly than the led to the idea that molds or bacteria or both were re- painted, indicating that the bacteria did not derive their sponsible for the trouble, since it is well known that certain source of nitrogen from the cyanogen compound, but from types can cause the formation of free alkali, and this alkali the duck itself or a material on the duck. in turn can decompose the green. Chrome greens are readily Kjeldahl determinations were run on canvas used for decomposed by alkalies, even in dilute solutions. awnings from different manufacturers, and the total nitrogen Various samples of painted striped awnings were obtained content varied from 0.16 to 0.23 per cent. Usually about to test out this idea. Pieces of awning, thoroughly wet with half of this nitrogen was readily soluble in water. I n the tap or distilled water, were placed in Petri dishes. These presence of water and of the proper temperature, this quickly dishes were kept a t 37" C. in a constant-temperature oven available nitrogenous material makes a fertile place for for various lengths of time. bacterial growth. Bacterial activity is shown by the speed Results usually manifested themselves in 24 hours, and in of production of free alkali. many cases 12 hours were sufficient. The pieces of canvas Samples of the unpainted duck were washed with warm gave very alkaline test reactions, and the characteristic water (to remove the water-soluble material), dried, and yellow discolorations were present on the green. In many painted in the usual manner. Tests on cloth treated in this instances the alkali present would be strong enough to fashion were then run by the methods previously described. destroy the green completely in a few days. Many of these tests were continued for as long as 6 weeks, A number of articles in the literature on the subject of and the color was unchanged a t the end of that time. In mildew state that oils, fats, and soaps enhance the action order to make the tests more severe, and to be sure that the of mildew and produce alkaline products. This sounded amine- or ammonia-forming bacteria were present, additional plausible a t first, since the paints contained suitable ingre- tests were made by folding badly spotted, infected green dients for this reaction to take place. I n the case of the awning duck within the pieces to be tested. Many of these green stripe, the alkalinity was developed from another samples were run for a 6-week period. The green showed source, however, which will be described in more detail later. no signs of bacterial action at the end of that time. It was Mold growth was very pronounced on some of the cultured also found that it is possible to wash the soluble material samples of awning, especially after a period of several days. from painted duck and then have the green remain free of When the duck was examined by means of a microscope, a yellowing, when tested in the usual manner. number of different varieties of mold were found. The first I n most of the above mentioned experiments where the conclusion was to place the cause of the yellowing on mold water-soluble nitrogenous products had been washed from growth. However, some samples of the green on the awning the duck, the test pieces gave acid reactions; in a few cases 579
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the reaction was neutral. I n no case did a n alkaline reaction develop during the culturing process. These tests were far more severe in the laboratory, where ideal conditions of temperature and moisture were maintained, than will ever happen in a practical way. As stated before, many of the test pieces developed a mold growth after being cultured several days. The mold apparently does not harm the color. The mold grows best when neutral or acid conditions and a small amount of water are present. Some of the test pieces would be decidedly alkaline on one spot and a short distance away would be acid to Congo paper.
SOLUTION OF THE PROBLEM Odd as it may seem, since chrome green is a mixture of Prussian blue and lead chromate, the author has not heard of any instances where Prussian blue alone on awnings has spotted. A number of samples were prepared using Prussian blue in place of the chrome green and were then exposed in the Petri dishes. It was found that Prussian blue has a somewhat faded appearance after a considerable length of time. This action is much slower than with chrome green and is not as noticeable. It may be that the lower pH value
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of a Prussian blue affords it more protection against the free alkali. A number of additional colors were used on awning duck, and the alkaline reaction was produced in practically all cases. If a color is not easily damaged by alkali, there naturally will be little or no change of the shade of the color. Cotton duck painted on both sides is much more resistant to bacterial action than the canvas painted on one side only. I n this case the water-soluble nitrogenous material is covered by paint and is not as readily available to the bacteria as is the case with unpainted duck or duck painted on one side. The real solution of the problem lies with the manufacturer of the cotton duck. Either the nitrogen-containing material on the canvas should be eliminated, or a less desirable method, the addition of an antiseptic to the cloth in order to prevent the growth of undesirable bacteria, should be used. A number of cotton duck manufacturers are doing considerable research on the use of antiseptics in the prevention of mildew. The successful application of an antiseptic in the prevention of mildew may also be successful in preventing the growth of the amine- and ammonia-forming bacteria. RECEIVED January 29, 1934. Preeented before the Division of Paint and Varniah Chemistry at the 85th Meeting of the American Chemical Society, Waahington, D. C., March 26 to 31, 1933.
Treatment of Waste from Dyeing and Printing ' c
FOSTERDEE SNELL,Foster D. SneI1, Inc., Brooklyn, N. Y.
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The laboratory examination of wastes from a constitutes about 10,000gallons, printing and dyeing establishment handling silk, containing about 1000 pounds does PieCe-dYeing and of soap and more than an equal printing on silk, silk-andrayon, and cotton indicates that the printing weight ofsericin. Of this, about cotton, silk-and-wool, rayon, and c o t t o n . The c o l o r s used are W L and ~ boil-off ~ ~ liquors ~ should be diverted. 25 per cent is discharged during principally basic and direct dyes. By SO doing, the remaining liquors can be the day and the remainder late blended and treated with 4pounds of copperas and in the a f t e r n o o n . Hydrogen The predominant colors vary 4 pounds of lime at a cost of less than 5 cents per peroxide bleach s o l u t i o n s are from season to season according discharged intermittently and to the fashion* The 1000 gallons to render them suitable for disamount to a total of 5ooo gallons off its own silk, using soap for the Purpose, and bleaches with hycharge into a dream containing 5 s h and plant daily. About 2000 gallons of drogen peroxide stabilized with life. sulfur d i o x i d e bath are dissodium silicate. It also does a charged daily. Every 2 hours minor amount of mercerizing. There is no hypochlorite there is a discharge of 2000 gallons of weak alkali, a total of bleaching, no chrome-dyeing, and no silk-weighting. The water 10,000 gallons daily. A sour in this department yields a dissupply used is both well water and city water, softened with charge of about 10,000 gallons daily. A mercerizing bath of zeolite. The water supplied and the waste accounted for 25" BB. is discharged only at about 6-month intervals. The balance of the waste from this department consists of miscelfurnish a rough cross check. laneous wash waters. SOURCES AND QUANTITIES OF WASTEDISCHARGE The daily discharge from the printing department consists The plant can properly be described as separated into three of 10 to 20 gallons of concentrated printing dye, hydrosuldepartments: dye house, boil-off and bleach, and printing. fite, formaldehyde, etc. This is accompanied by about 25 Quantities of waste do not necessarily bear any relation to to 50 gallons of highly contaminated wash water. A furthe volume of production. For the purpose under discussion ther discharge of less contaminated wash water amounts to here, the plant may be most clearly visualized as a producer 5000 gauons daily. I n addition to the above wastes the plant has a working of certain effluents in terms of normal operation. The dye house discharges 100,000 gallons per day of ex- population of approximately 350 persons, furnishing 20,000 gallons of sanitary sewage per day. hausted dye solutions and wash water. The boil-off and bleach department discharge 200,000 COMPOSITION OF WASTES gallons per day of mixed waste. The boil-off discharge alone The individual wastes were sampled a t half-hour intervals 1 This is the sixth of a series appearing under the general title "Chemical effluent Of each type and the throughout the Treatment of Trade Waste." Part I appeared in Am. Dyesluff Reptr., 16,54 was used to furnish data on the composition of the wastes. (1927) For Parts 11, IV,V, seefootnotes, Part 111 was not published. HE plant under discussion
