by E. Hope Allen Yankey, appearing in The Shepherd, October 1997
Each year I get another crop of wool from my sheep and more gray hairs appear on my head. So, when I get the urge to dye, I just want to dye it all—the wool and the hair. Actually, wool and hair dye similarly, because they are both ANIMAL PROTEIN fibers (they contain carbon, hydrogen, oxygen, nitrogen, and sulfur) unlike cotton, flax, and rayon which are PLANT CELLULOSIC fibers (they contain carbon, hydrogen, and oxygen). Not all dyestuffs will dye all fibers. Some will dye both animal and plant fibers, but must be treated very differently during the dyeing process. All dyestuffs are "chemical" dyestuffs—all the things that make up the earth and our bodies are chemicals, for that matter. It's just that some "chemical" dyestuffs occur naturally (i.e., for example, walnut hulls, onion skins, dandelion flowers, cochineal bugs, etc.), and can be used for dyeing wool in their natural state, but may require additions of acid, soda ash or lye, and "metallic" formatting agents which attach the dyestuffs to the wool fibers, Different mordants (or metallic compounds) produce different colors. They also provide better wash and light-fastness than would be attainable otherwise. Some natural dyestuffs may require an intermediary “chemical” reaction to make use of the “raw'' coloring matter that is obtained either from plant or animal sources. Indigo, for example, one of the oldest recognized natural dyestuffs, is of this type. It cap be synthesized from coal tar derivatives and used commercially for dyeing both wool (and cotton), but must be, whether obtained from the Indigo plant or synthesized commercially, ''reduced'' or made soluble (able to dissolve) in water with the addition of caustic soda (Sodium Hydroxide) and Sodium Hydrosulphite. Synthetic Indigo has been one of the more significant dyestuffs to be utilized industrially, because it is equally easy and cheap to manufacture, easy to apply, imparts good color, and provides excellent light and wash fastness.
The majority of synthetic dyestuffs designed for dyeing tool are Classified as ACID dyes—because the teethed used to get them to bond to wool requires the addition of acid to the dyebath, sulfuric or acetic, commonly. These are marketed by a variety of companies (Ciba, Rite Chemical, ProChemical, for example) under different trademarks, but are often listed as “Acid Green No. __,” “Acid Black __,” etc. The Jacquard Cushings, and ''GayWool' dyes are ACID dyestuffs. However, Rit and Dritz dyestuffs that are marketed in grocery stores for home use, are DIRECT dyes designed for “direct” application (i.e., dissolve dyestuff in water, add fiber, a little table salt, and heat) to cellulosic fibers, cotton, rayon, etc. They were not developed for wool, and, although they will impart color to wool, the effect is more often like that of staining rather than true “dyeing”—it is difficult to obtain any great ''depth'' of color or, more importantly, fastness properties. The Kool-Aid, Jello, and food-coloring dyestuffs fall into this class as well—they are safe for kids, safe for adults, yes, but not “substantive” for dyeing wool fibers, yarns, etc. where durability and fastness are needed. There are two major types of the ACID dyestuffs synthesized for wool use. (You may already have figured this out on your own.) One type will dye a given “lock” of wool fibers more evenly lengthwise, from the fiber root to the tip, or a mixture of blended wool fibers—whether gathered from the rump-to-the-belly-to-the-shoulder-head-and-neck wool from one fleece, or from both lamb's and mature sheep's fleeces, or blended from fleeces of different wool types (fine, medium, and coarse). These are the Levelling Acid dyes which come with the recommendation that Sulfuric Acid be used in place of the weaker Acetic Acid we are most familiar with using to dye wool (vinegar is a 5% or less solution in water of Acetic Acid). The Levelling Acid dyes exhibit poor fastness properties. The other type, which you may have stumbled across, provides the “heather'' like effect or “variegated'' look—individual fibers take up these dyes more strongly at their weathered, more porous tips, while blended fibers from the various parts of a given fleece or fleeces bind these dyes very differently depending on their “type,'' diameter, crimp, and the amount of degradation due to dirt, grease, and sunlight exposure. These Acid dyes and are applied from a weakly acid bath, utilizing Acetic Acid. The Milling Acid dyes provide excellent substantivity or fastness properties on wool. They are great fun for the spinner, weaver, tentmaker, etc. who chooses to dye their own wool, and can provide a variety of color effects. There are many ACID dyestuffs which fall betwixt and between the Milling and the Levelling Acid types with equally betwixt and between properties and affinities to dye wool evenly, “level.”
Not significant to industry at this point for dyeing wool (the exception: carpet blends with nylon and polypropylene) are the newer synthetic dyestuffs classed as REACTIVE dyes, which you may recognize as those marketed under the following trademarks, for example: both Procion M (cold dyeing) and Procion H (hot dyeing), Cibacron, Reaciofix, Remazol|, Levafix, Lanasol, Kayacion, and others. REACTIVE dyestuffs are chemically MORE reactive (makes sense)—they dissolve more readily in water, they bond more readily to whatever fiber they are used to dye (actually, they bond equally well to the water molecules themselves), and are, consequently, more substantive, less likely to bleed or fade with repeated washings and exposure to light. These dyes are very popular now with crafters. They impart a greater degree of brilliance at surprisingly deeper and deeper shades of yellow, red, blue, green, brown, black, etc. whether used as individual dyes or as mixtures to obtain all hues (all colors) than all other natural or synthetic dyestuffs. Their use has been primarily on cottons. Little has been done to research or examine commercially the use of REACTIVES for dyeing wool. The method used in trial experiments and university research projects suggest the best technique for dyeing wool with REACTIVE dyes (as many of you have discovered on your own) utilize the same basic principles used for dyeing wool with conventional Milling Acid dyestuffs—from a weakly acidic bath at or near boiling. Acetic or Hydroxyacetic (Glycolic) or Formic Acid work better than vinegar because they are stronger. Sulfuric Acid is much stronger and more hazardous to use around the house and is not needed for REACTIVES on wool. REACTIVES vary greatly in their ability to evenly dye your wool fibers—you can use this to your advantage to create color variations along with individual fibers or in blends of different types of fibers. As pointed out earlier, the same is true with the use of the ACID dyestuffs on wool. It will take some experimenting with different dyes and with different dye mixtures to get a feel for what is possible beyond just the “accidental.'' (Personally, I prefer the use of REACTIVES because they can give greater depth of shade and brilliance than is attainable otherwise—it is the nature of the chemistry of these dyes that will do this. Their ability to react with wool fibers gives excellent fastness properties as a result.)
All wool is typically dyed—whether “loose,” spun, woven, felted, or knitted—in a heated water bath or “liquor” at temperatures near or at boiling. (Little dyeing occurs below 160 degrees Fahrenheit.) That's whether you're dyeing in a pot or kettle in your kitchen, outside on a backyard barbecue grill or 'specially designed dye-pit, or in a wool-dyeing facility in industry. Still, dyeing can only, really, take place if the dyestuff, whether natural or synthetic, is made soluble in water and is then forced to enter and bond with the wool fiber molecules. For all us home bodies fascinated with dyeing our own wool fibers, yarns, fabrics, and garments, there are some practical considerations to be made to get not only the color we desire, but also, insure wash and light fastness, and, in turn, retain residence, softness, and wool quality. Below are some tidbits of information I've gathered along the way (30 years) which may aid you in dyeing wool for both fun and profit!
*Wool is scaly, not smooth like hair, and comes in a variety of scaliness, crimp, diameter, whiteness, and length. This affects dyeing. Finer, crimpier wools may take up the same amount of dye as stronger, less crimpy wools, but will appear duller because their physical make-up reflects less overall light to our eyes than the more coarser, lustrous type wools. The whiter and brighter the wool you start with, the more brilliant and intense the color you'll obtain when the wool is dyed, no matter the dyestuff or method used in dyeing. No wool can me made whiter than it is—i.e., wool cannot be "bleached" before dyeing (like cotton). And, naturally colored wools can really only ever be tinted or stained, not dyed.
*Weak Acids (Acetic, Hydroxyacetic, and Formic) do not generally affect wool quality—strength, softness. that illusive thing we call “feel”/“handle”—and so dyeing in a typically, weaker acid environment (pH 4-6) produces no detrimental effects. On the other hand, the use of strong soaps and alkaline detergents, like Ivory cake soap and Ivory powdered detergent, will affect wool quality, and should be avoided during the scouring or washing of wool prior to dyeing. (The cold water, alkali technique used to tie dye cottons with Procion M type dyes can damage wool strength and wool softness of “feel”/“handle,” making the wool brittle and harsh. It is recommended that you use the more conventional acid bath technique even when dyeing wool with the Procion M type dyes.)
*Dyeing at or near the boiling point is generally not harmful for reasonable periods of time—30 to 60 minutes or even two or three hours. However, the less the time that is required to obtain the “color'' desired, the less chance of the dyes migrating (moving towards the more porous tips) along individual fibers or among competing blends of fibers (affecting levelness). I prefer dyeing at temperatures of 185- 195 degrees Fahrenheit near but not boiling. This lessens the chance that wool will become harshened, shrink, and felt due to the increased heat and activity at the boil.
*Also , along these same lines, “SHOCK'' is damaging to wool. Always GRADUALLY increase and decrease the temperature subjected to the wool fibers prior to and after dyeing. Avoid extremes in going from hot to cold and vice versa. GRADUALLY rinse, starting with hot water and decreasing the temperature to that of room temperature in your final rinse. (You can “cheat” by using a mild conditioner that you would use on your hair to impart softness, but be sure and rinse well afterwards. Vinegar makes an excellent final rinse, also.)
*The use of Sodium Sulphate or Glauber's Salt during dyeing will assist leveling or even distribution of the dye throughout the fibers, but keep in mind, once reacted with the fibers, as the REACTIVE dyes are prone to do, you're done, so to speak. Slight additions halfway through the dyeing process, especially with Milling Acid type dyes, may aid in the leveling process.
*Dry wool is more difficult (just takes longer) to dye than wet wool. This leaves you two choices: one is to wash, rinse, and dye in sequence, the other being to wash, rinse, dry, and store wool which, when preparing to dye, you “wet our” first in water containing a very small amount of mild shampoo or detergent for approximately one (1) hour. This lessens your overall time and exposure in the dyebath to high temperatures, etc.
*Also, the grease in wool has to be removed before dying can take place. Otherwise, you may simply be dyeing the grease and exhausting dye where you don't want it. I wash wool in cheap shampoo or Orvis (industrial strength shampoo to which a small amount of Sodium Sulphate has been added) in gradually, increasingly warm water, and rinse in a vinegar bath prior to dyeing. There will still remain a small amount of grease on the fiber unless you work really hard to remove it via repeated washings at high temperatures. I find a small amount desirable (see below).
*Hard water can affect dyeing results. If your water is known to contain much calcium or other minerals, add a small amount of Borax to your dyebath liquor (approximately one teaspoon per gallon water). If you get your water from a chlorinated, fluorinated source ''in town,” l suggest you let it stand in an open pot or kettle several days prior to use. Otherwise, use rainwater, if possible. Chlorine and Fluorine will affect dyeing, where as acid rain might, but, wool, being dyed from an acidic bath will, perhaps, be less affected by acid rain than by other water impurities.
*After dyeing, it is important that you wash your now dyed wool to remove excess dye that did not attach itself to the wool fibers. Again, some dye may have exhausted itself onto the grease, or have, as is the case with REACTIVES, remained attached to the water molecules. This needs to be removed, especially if you’re selling dyed wools. Often, intense shades will appear to “bleed” more during this final wash, but it is only the excess dye that is being washed out. Rinse in GRADUALLY decreasingly cool water until the water is clear. Any remaining grease or lanolin will precipitate back onto the wool fibers and create a nice handler.
*The use of any dye can be hazardous, but need not be sufficient cause for great alarm.Never just “throw'' powdered dye into the dyebath. Not only do you risk breathing the dust, but the powdered clumps are often slow to dissolve and can get trapped as such among the wool fibers. I know you might think the use of powdered dyes could produce interesting effects, but consider the risk and the waste. (Some people feel the need to wear protective masks, etc. I just don 't like to wear them—but I do wear gloves, most of the time. The use of “natural” dyestuffs obtained from plant and animal resources does not remove all hazards. Some mordants are known carcinogens—Chromium being the more commonly encountered of today's mordants in use. Mercury, Copper, and Lead were extensively used as mordants in the 1800's, but, obviously, are not being recommended for use now. Some plants are known irritants, some are poisonous, and many can cause severe allergic realigns in some people—goldenrod, ragweed, sumac, poison ivy, pokeweed, choke cherry, dogbane, etc. The biggest threat from synthetic dyestuffs (and, in some instances, natural ones as well) occurs as a result of the nature of the dyestuff as prepared—in POWDERED form—and not the chemical structure itself. Some REACTIVE dyes carry a warning label indicating that they may irritate respiratory passages. I have had asthma my entire life, so I do know what respiratory irritants can do—but, again, the vapors that escape from the dyebath are a far more serious threat than repeated exposure lo the dyestuffs themselves, unless you're working day after day in a factory where large, open vats are used for dyeing and poor ventilation is the rule, not the exception. Remember this: Breathing the vapors from a near boiling solution of Acetic Acid or vinegar can be harmful with or without the addition of dyestuffs! The best way to avoid problems is simply follow these rules: First, dye either outside or in a place with excellent ventilation (Under a hood is goodl). Second, always dissolve powdered dyestuffs and chemical additives in water prior to adding them to the dyebath liquor (add a little cold water to the amount of dyestuff or additive you intend to use and make a paste, then continue to add slightly warmer water to the paste until you have the dye (or additive) completely dissolved in a reasonable amount of water [1 to 2 cups]). REACTIVES DYE SKIN READILY AS WELL AS WOOL . . .) And third: If you experience a problem, call someone you know who has had more experience with dyes and dyeing than you or OTHERWISE, GO BACK AND READ THE DIRECTIONS AND THE WARNING LABELS!
*Additions of small amounts of acid may be needed during the dyeing process to achieve the compete exhaustion of some dyestuffs. this may be accomplished by trial and error (observation) or my monitoring the pH or acidity of the dyebath liquor. You can always reuse the dyebath to dye other wools, but completing the exhaustion of any one dye from its original dyebath solution will tend to impart greater fastness properties, less bleed problems, and more consistent colors. You can utilize all of these factors to produce any great number of color effects and color combinations with a little ingenuity and design. It helps to keep a notebook of all the dyestuffs you've used and all the dyebaths you've created—who knows, someday, MAYBE, even I'll try it!
*Eight Years of College in Textile, Fiber, and Color Chemistry at both North Carolina State University and Lehigh University, Ten Years of Industrial Experience, and an Overlapping Thirty Years as Shepherd, Shearer, Dyer, and Feltmaker, Twenty-five devoted to the Coopworth Breed and use of Coopworth wool.
*Laboratory Course in Dyeing, C.H. Giles, The Society of Dyers and Colourists, Great Britain, 1966.
*Wool Science: The Chemical Reactivity of the Wool Fibre, John A. Maclaren and Brian Milligan, Science Press, Australia, 1981.
*Wool and Mohair, Thomas Hamsworth and Graham Day, Inkata Press, Australia, 1990.
*Color Index Reference Manual, Fourth and Fifth Volumes, Latest Edition, Available from the NCSU School of Textiles Library, 1992.
*NCSU School of Textile Staff Members: Dr. James Rucker, Dr. Leon Moser, Jeff Krause, and Lynell Williamson.
*The Dye Pot, Mary Frances Davidson, published by author, Tennessee, United States, 1974.*North American Dye Plants, Anne Bliss, Scribner's Sons, New York, United States, 1980.