Acid Dyes
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ACID DYES
Choosing the Right Dye
Unfortunately one one kind of dye will not do everything. So you will have to chose which dye is right for you and the task at hand. I will discuss the advantages and limititations of acid dyes to help you make an informed choice.
Types of Fibers
To select a dye, you must know the chemical composition of the fiber you want to dye. Cotton, linen, ramie, and all vegetable fibers are composed of cellulose; they’re referred to as cellulostic fibers. The chemical group that reacts with the dye molecule in cellulose is the hydroxyl group, -OH. Wool, mohair, cashmere, silk, and other animal fibers are made of protein. In all protein fibers, the reactive group is the positively charged amino group, -NH3+. These are a part of the peptide bond that strings the amino acids together. The protein fibers can have additional reactive groups that are unique to each fiber, depending on the specific amino acids in the protein. Wool has a lot of the sulfur-containing amino acid, cystine, and consequently forms disulfide bonds. Silk is formed from amino acids that have a few hydroxyl groups that can also bind dye, these are the same reactive groups as found on cellulostic fibers and so silk will also color with dyes designed for cellulose.
Some synthetic fibers are made from regenerated cellulose: rayon, viscose and Tencel. They take up the dyes that react with cellulose. Nylon is a synthetic polyamide fiber having the same reactive groups as proteins, although not as many sites. Nylon dyes with the same dye as silk or wool, but some nylons, and there are several kinds, some that may dye a light color only, because of the reduced number of dye sites. Other synthetic fibers, like polyester, are more difficult to dye without industrial equipment.
ACID DYES
This ia a very large group of dyes, old ones and new ones. Dyes are called acid for two reasons:
1. they are the sodium salts of colorful complex organic acids,
2. and the dye bath is acidic, pH 2-7.
A salt is an ionic compound that separates into two oppositely charged particles, or ions, when dissolved in water. Since acids dyes are salts, when you dissolve them in water, you get a positively charged sodium ion and a negatively charged acid dye ion.
NaDye(crystalline) « Na+ (aqueous) + Dye- (aqueous)
This negatively charged dye is attracted to the positively charged binding sites on the protein fiber, -NH3+. Because opposite charges attract, this forms a very strong ionic bond.
If the negatively charged dye ion can get to the positively charged dye binding site we have colored cloth. The pH must be controlled to assure that the dye and protien are properly charged.
Classes of Acid Dyes
There are many different classes of acid dyes, leveling, milling, chrome, premetallized that have to do with the structure of the acid molecule. I want to use a very practical classification, by the type of dye bath required for their application. Acid dyes can be applied in dye-baths with stong acids, weak acids or neutral ones. The structure of the dye dye detemines which dye bath is appropriate.
Acid dyes requiring a strong acid dye-bath
These are quick to apply, level easily, have a broad pallate with bright colors. Their high solubility in water limits their wet-fastness. We do not use these dyes in the home environment because concentrated sulfuric acid is very corrosive, flesh included, and we don’t have the techniques, safety equipment required nor the utensils for dealing with such a strong corrosive acid.
Acid dyes requiring a weak acid dye-bath
These dye only require a weak acid such as acetic acid, commonly found in vineger, for the dye bath. Vinegar or concentrated acetic acid can be used safely by small scale dyers. Weak acids can be combined with their salts to form a buffer ; a buffer helps to maintain the pH constant as you add the silk and dye. A buffered dye bath requires little monitoring of the pH during dyeing.
The iso-electric point of wool is pH 4.5, this is the pH at which wool, and by extension most protiens, are at their stongest. If you can apply the dye at a pH near 4.5 these are the gentlest conditions for the protien fiber and you will notice the wonderful hand that the dyed goods has at the end of the dye process. For the substrate, these are ideal conditions.
Good fastness properties can be obtained with dyes in this class. A small amount of sodium sulfate (2-5% WOF) can be used to increase levelness. A wide range of colors is available with some weakness in the very brightest colors.
Many acid dyes we use fall into this category; Lanaset, Kiton…
Acid dyes requiring a neutral dye-bath
These dyes are applied in a nearly neutral dye–bath, with an acid salt such as ammonium sulfate or ammonium acetate both of which are white crystalline solids. At the boil, these salts decomose slightly, giving off ammonia as a gas and leaving behind minute amounts of sulfuric acid.
(NH4)2SO4 = 2NH3(escapes as a gas) + H2SO4
As the bath boils sufficient acid accumulates to promote proper exhaustion. This is pretty easy, you add some salt to the dye-pot intially and just let it decompose slowly.
These dyes do have limited solubility, do not level well and require a long carefully controlled dye run. The low solubility limits their use in direct applications where one works from concentrated dye solutions. In the presence of even a weak acid these dye may strike fast and /or precipate out of solution. These tend to have duller colors.
CLASSIFICATION OF ACID DYES
|
| Strong acid dye-bath | Weak acid dye-bath | Neutral dye-bath |
| pH acid required | 3.5 2-4%sulfuric acid | 3.5-5.5 2-4% acetic acid | 5.5-7 ammonium sulfate |
| solubility | high | intermediate | low |
level dyeing | Very good | intermediate | fair |
dyeing time | Relatively short | intermediate | longer time |
| wet-fastness | fair | better | very good |
| color range | wide range bright colors
| intermediate | moderate brightness |
| examples |
| Lanaset Kiton | Pro WashFast Nylomine Miyako Ricoamide |
Characteristics of All Acid Dyes
Acid dyes exhaust well, 96-100%, meaning that there is little dye in the dye bath at disposal time and that nearly all of the dye is on the fiber. This property also makes them easy on the environment; there is less chemical residue for disposal. Disposing of weak acid or neutral dye bath is no more problem than getting rid of pickle juice. Acid dyes require very small amounts of salt and other auxilliaries, as opposed to the massive amount of salt required for fiber-reactive dyes. These dyes are relatively insensitive to the amount of water in the dye bath; a handkerchief dyed in a liter of water and one dyed in 4 liters would be very close in color. Solution of acid dyes are stable for long periods of time. This means that you can prepare stock solutions of the dyes and still use them 6 months later. The pH needs to be carefully controlled, in the range designated, and heat is required for all processing, including direct application. This means all painting, stamping printing with acid dyes must be steamed or heat set.
Dye Sets
Dyes come in sets, or families of related compounds that form the fiber-dye bond under the same or similar conditions. Each manufactured color is a pure compound, meaning that it contains only one kind of dye molecule. These manufactured colors can be mixed to created many more colors; dye repackagers for the craft market sell mixed colors. Some sets have many manufactured colors. Lanaset, a dye set I use extensively for immersion dyeing, has 13. Others have fewer; a sulfur dye set may have only one--a black. Often it is unclear which dyes are manufactured colors. A simple method for testing for mixed colors is is to blow a bit of the dye across a damp cloth ; pure colors will have all the dots and spots the same color, mixed colors will show the component colors.
There are two advantages of using only manufactured colors: When you mix the colors, you can reproduce the colors. It is also cheaper to buy only a few dye colors. This will not limit your palette, because you are mixing from the same set as the repackager.
Dye Processes
We can divide dye processes into two categories: immersion dyeing and direct application.
In immersion dyeing, the dye is dissolved in a dye bath. The fabric is immersed in the dye bath and processed. A typical immersion process uses a lot of water, has a means of agitating the goods or circulating the bath, requires heating or temperature control, and is processed for an hour or more. The heat and time provide energy for the dye-fiber bonds to form. The term exhaust dyes is used to describe dyes that can bond all the dye molecules onto the fiber. The term exhaust is also used to describe the percentage of dye in the dye bath that is fixed to the substrate at the end of the dyeing process. Well-exhausted dye baths are nearly colorless. Pale colors can exhaust well; blacks never exhaust completely.
Direct application refers to any process where the dyes are put directly on the cloth in a concentrated concoction without a bath. Typically, the dye is dissolved in a small amount of water with other auxilliaries such as thickeners, acids, alkalis, or salts. This dye mixture is then applied by printing, painting, stamping, flinging, or other imaginative methods. Subsequent steps, batching or steaming, are required to form the dye-fiber bonds; this is called fixing the dye. The colored goods must now be washed to remove the auxilliaries that were in the dye mixture. When done properly, nearly all the dye fixes to the cloth, even dyes that do not exhaust well in a dye bath. This method does not require heating of large volumes of water nor disposal of dye baths, making it more economical and reducing environmental impact. Small-scale dyers rarely use direct application to lay down a large field of level color. In most direct-application techniques, level dyeing is not a goal.
Immersion dyeing usually gives the best penetration, meaning that the entire cross-section of the fiber is uniformly colored. Direct applications may reach only the surface of the fiber.
Packaged Dyes
Packaged dyes are quick and easy; just follow the instructions. As there is no magic universal dye that works for all fibers, these packages contain more than one type of dye and multiple assistants like surfactants, salts, and leveling agents. Say you’re dyeing a nylon tutu: One of the dyes fixes to the nylon, while the dyes for cotton go down the drain. The cost of one package is nominal, but if you dye large quantities, it would become expensive. You are paying for the work of premixing the color and the dye assistants as well as the dyes you are not using. If you just want to play with some shibori techniques, use packaged dyes for any immersion process. You can move on to other dyes when you need more control over color, fastness, or cost.
Silk Paints
Another option for beginners is silk paints. Many brands and colors are available, and they come in little bottles ready to use, so you don’t need much equipment. Silk paints are often used in techniques requiring gutta lines to control the spreading. The color you see as you paint is close to the final color, and the colors are mixable. You can focus on your painting with little thought of technique. These so-called paints are generally concentrated solutions of acid dyes. Because these dyes have limited solubility, alcohol or another additive is added to the mix to increase the solubility. The alcohol does evaporate, and exposure to the fumes has become a health issue for some people who work extensively with these products. Silk paints require a fixing process--usually steaming, but some involve a chemical fixative. Follow the instructions given by the manufacturer. You can improvise a steamer in your kitchen (but don’t use equipment you will cook in); specialized steamers are also available. Using silk paints could be a way to explore some of the resist techniques in shibori.
Like packaged dyes, silk paints can become expensive if you need large quantities. My biggest objection to these dyes are the wimpy colors I get on very light-weight china silk, which I like to use. If you use a heavier or denser silk --charmeuse or crepe de chine-- you may find silk paints satisfactory for you.
LANASET DYES
Lanaset dyes are manufactured by Ciba Specialty Chemicals and first became available to the small scale dyer in the USA in the 1980’s. They are sulphonated 2:1 metallized acid dyes that are applied under acid conditions, a pH of 4.5-5.0. There is little chance for damage to the silk at this pH, which is ideal for silk. The silk comes out of Lanaset dye baths soft and lustrous. The Lanasets have very good wash- and light-fastness. They have excellent exhaustion, 96%, and all the colors tend to exhaust at the same rate, a real advantage when dyeing a mixed color.
There are 13 manufactured colors (see Table ) and the palette is more subdued than fiber reactive dyes, but I like the Renaissance colors. There are 3 outstanding colors in the set, the violet, the turquoise and the black. The violet is very brilliant and adds fire to fuchsias, purples and burgundies. The turquoise is also flashy and makes bright greens and beautiful aquas and blue-greens. But black is the star for me, it is a neutral , jet black. This quality of black is very hard to mix yet 50% of the goods dyed in the USA are dyed black. I use a lot of black as a base color because I have never achieved black in an overdye; I can get grays and maybe even charcoal, but never a true black. Blacks are always hard to dye, you must saturate the all dye sites on the fiber to get a true black. To get black you use a the highest DOS, 6-8%, process longer and in general use the most extreme good dyeing conditions to get a deep black. Over dyeing does not have these optimum dyeing conditions needed for true black.
DOS, or depth of shade, is a central concept to controlled dyeing. The ratio between the fiber and the dye is what determines the darkness of the color. The same black dye at DOS of 0.8% will give you a pale gray, at 3.5% a charcoal grey and at 6-8% a black. To understand more about this kind of calculations see the chapter on color and formulation.
Lanasets do have a weak red range, although there are 3 red dyes, none of them have a brilliant fuchsia base. I use a red from a different set of dyes to expand the red color range. I use a very bright blue based red, Ricoamide Red 3BN 140, sometimes called polar red. This allows me to get bright reds, fuchsias and vibrant red violets. This dye is compatible with the Lanaset dyes but the pH must be 5.0. Unfortunately the fastness of this dye is much less than the Lanaset, so process it longer, let it air dry for 24 hours before washing and in general be much gentler with it. It does discharge to an off white but the decoloration happens very fast compared to the Lanaset dyes. So if you have a mixed color with both Lanaset and Ricoamide and you discharge it, the Ricoamide will discharge first and completely before any of the Lanasets show any color change.
Another aspect of the Lanaset dyes that I like for my shibori has to do with the discharge colors. All the Lanaset dyes do discharge and some go to an off-white but many go to a more interesting color. The violet discharges to a yellow (see Table for all the discharge colors). These discharge colors can add an exciting halo of color to your shibori work.
The Lanaset dyes are relatively insensitive to the liquor ratio and that allows us to work at long, 40:1 or greater, liquor ratios required to get an even dyeing on silk or to cover our tortured and scrunched silk. These dyes are composed of large molecules and therefore diffuse slowly and have a slow strike rate making them unsuitable for over dyeing the poles but easy to get level colors. The dye bath contains little at the end of dyeing and is therefore easy to dispose.
Since Lanaset is an exhaust dye the DOS are pretty low, but of course it depends on your process. But for a rule of thumb, off-whites are >0.25%, pale colors 0.25-0.80%, midtones 1-3%, dark colors <3% and black 6%. If you get good exhaustion you can probably reduce the DOS and with poor exhaustion you may need to increase them a bit.
The process for immersion dyeing with Lanaset dyes is simple. Prepare the dye bath with the auxiliaries, adjust the pH. Add the silk, then the dye, heat slowly to 85°C/185°F/185°F. Hold for 1 hour, cool. Remove the silk from the dye bath, hang to dry.
AUXILIARIES FOR LANASET
Acetic acid-sodium acetate buffer
The dyebath should have a pH of 4.5 –5.0 during the dyeing procedure. Everytime you add something, silk or dye, to the bath the pH can change. An acetic acid-sodium acid buffer is used to maintain the pH relatively constant even with additions. The sodium acetate and acetic acid work as a team, so as long as both are present they can keep the pH constant. Sodium acetate is a white salt available from chemical or dye suppliers, acetic acid is available as a 5% solution at the grocery store (white vinegar), a 56% solution from dye suppliers, or as glacial acetic acid (96%) from chemical suppliers. Acetic acid is also used by photographers so you can get small quantities at places where photographers buy chemicals for developing, just be sure that it is colorless, I have seen acetic acid for photography that is yellow. You will use a large amount of vinegar because it is so dilute. Shipping the 56% acetic acid is expensive because it must be treated as a hazardous material in transit. If you can find a local source it will be cheaper in the long run. I buy glacial acetic acid from a local chemical supplier, I use 2-4 gallons per year and I dye a lot. The most concentrated acetic acid is called glacial acetic acid because it will solidify, looking like a glacier, just below room temperature. Acetic acid is a lachrymator (makes you cry like onions) and strong acids are corrosive to flesh so take precautions, wear apron, gloves and goggles) when handling concentrated acid. I dilute the glacial acetic acid 1:1 with water and then use the 48% acid for the dye baths because it is easier to handle.
Some dyers have started using citric acid in place of acetic acid. Citric acid is a white crystalline powder and much easier to transport and less dangerous to flesh if you spill it. In many cases the substitution of citric for acetic acid is fine but not here. The acetic acid and sodium acetate make a buffer system and changing one component destroys the buffering capacity. You can make a buffer of citric acid and sodium citrate( or soda ash) but is works at a different pH than the acetic acid – sodium acetate buffer, citric acid-sodium citrate buffer works best at pH3.1, too low for Lanaset dyes. Vinegar is easy to use.
I add 1 mL of acetic acid for each liter of water that I have in my dye bath and a tablespoon of sodium acetate, just keep a record of how much you added for your dye pot and then use that amount the second time. How much you will need depends on the pH of your water. Just remember that you need both of these additives to create the buffer solution and the amount of each is not important , you just add enough to get to the right pH. If you measure the pH and it is too high, >5.5 , you need to add more acid, drop by drop, to lower the pH and if the pH is too low, <4.5, you need to add sodium acetate, tablespoon by tablespoon, to raise the pH.
Glauber's salt or sodium sulfate
This salt slows down the bonding of the dye to the fiber and encourages more even dyeing. The sulfate ions, SO42-, from the salt compete with the dye, also an negatively charged ion, for the dye sites. The glauber’s salt is diffused into the dye sites before the dye. You can use more salt to slow down the reaction and less to speed it up . It also enhances exhaustion. A small amount is used, 2- 5% WOF for an immersion dyeing silk. You can buy small amounts from the same company that sells you the dyes or you can buy 25lb. bags from your local chemical supply houses.
Albegal SET
This amber viscous liquid is a surfactant designed to be used with the Lanaset dyes, it is a retarder/leveler to encourage level dyeing. It also improves the compatibility of the dyes, and promotes migration and exhaustion. Use 2% WOF for silk, too much will interfere with the processing. You can change the amount used to get the effect that you want. This will foam up like most surfactants. Buy it with the dyes.
THE PROCESS
Using the WOF of your silk, calculate the dye and additives required.
PREPARED THE DYE BATH
Prepare the dye bath in a inert vessel large you can heat. The amount of water in the dye bath should be 30 - 50 times the WOF. (Remember 1g of water equals 1mL of water.) Have enough water to allow all the silk to move freely. The water which should be not be hot, >40°C/104°F. If the water is hard, add sodium hexametaphosphate. Adding the water softener makes the bath cloudy or milky. Add a spoonful at a time until adding more softener does not change the appearance of the bath. This precipitates the interfering substances out of solution so they can no longer react. Then add the glauber’s salt, acetic acid and sodium acetate and stir to dissolve. Measure the pH and adjust the pH to be 4.5 to 5.0.
ADD THE SILK
Add the wetted out silk carefully so that it is all is submerged below the surface of the dye bath. If a bubble of air makes some of the silk float above the surface of the dye bath, that part will not dye. Fan folding can help as well as holding the one end as you push the other end into the bath, this leaves channels for the air to escape. Poke at the silk with a stick to get rid of the bubbles and move the bath around some. Avoid stirring in such a manner that the goods become one big clump in the dyebath. Run the dye bath for 10 minutes (no heat).
ADD THE DYE
Remove the silk from the dye bath and pour the disolved dye into the bath straining it. Stir it for a bit to make sure all the dye is dissolved and evenly distributed through out the bath. Then return the silk to the bath. When I dye scarves I add them one at a time to make sure each one is totally beneath the surface of the dyebath. Run the bath of 10 more minutes without heating.
LEVELING AND HEATING
The hardest part of pot dyeing is in moving the goods so that you get level dyeing. This is the method that I use for pieces of cloth or scarves:
Remove the silk from the bath. It should be a uniform light color now. Reintroduce each piece separately, opening it up in the process. You are doing two things with the silk, you are looking to see how even the color is and you are making new folds in the cloth so that it will dye more evenly.
If the silk looks fairly even you can now start to heat the dyebath. As the temperature rises you will need to will need to ensure that the color continues to go on evenly. Slow heating will give you more even dyeing. Ideally you would like the temperature to rise one degree each minute. I just set a temperature goal, say +20°C in 20 minuntes, set a timer and check the pot when the timer buzzes. I try to take the silk out of the bath and reintroduce it 2-3 more times before the temperature reaches 70°C/158°F or when it is too hot to handle. If the color looks even I stop with 2 times, but if the color is still uneven I continue taking the silk out, refolding it and putting it back in. If you heat it too fast you won’t be able to get the silk in and out enough before it is too hot to handle.
Even a piece of shibori that is all tied up will benefit from movement in the dye bath. You want the dye to reach all the accessible areas. You can move it around with a stick but sometimes you will need to put gloved hands in the dye pot and move the silk with your fingers.
Raise the temperature to 85°C/185°F, and hold it there for an hour. Holding the temperature at 85°C/185°F can involve turning the burner on and off, or covering the pot or setting the pot over the pilot light. This is where you must take care not to damage the silk. The dwell time can be adjusted; if all the dye is exhausted you can stop heating and if you are trying for a true black you might want to increase the time dramatically.
COOLING
Allow the dye bath to cool down to at least 40°C/104°F. Take the lid off. I often leave the pot set overnight to cool down. A lot more of the dye fixes as the pots cools. You can use a fan to hurry the cooling. When it has cooled down, you can remove the silk and hang to dry. I spin mine out in the washing machine to make it easier to handle. The dye is still active until it is dry the first time so you don’t want to wash it before it has dried and the heat of the dryer can change the color a bit.
Once dry you can wash it once in a gentle cycle, hot water and a gentle detergent such as Orvus Paste. There will be very little if any loose dye in the wash water.
ADJUST AND ADAPT
This procedure is given as a starting place. If you are dyeing a pale color and the dyebath is exhausted, that is nearly colorless by the time you get to 85°C/185°F you won’t gain anything by heating it longer. On the other hand for very dark colors you may want to heat longer.
Evenness in very pale colors can be a problem because all the dye fixes so quickly. To increase levelness keep the starting temperature low, increase the amount of water in the dyebath, or add the dye in portions- add 1/3 of the dye and let that process for a bit, remove the goods, add another 1/3 and process again making sure there is good contact of all of the goods with the dyebath and then add the final 1/3 of the dye. You will learn what works for you.
Lanaset has been successfully dyed in a washing machine. The agitation of the machine will increase the levelness of the dyeing. But you can not heat to 85°C/185°F in a home washing machines so the exhaustion will be down.
NYLOMINE DYES
| PRO CHEM NAME | C.I. NAME | COMMENTS |
| WFA FlavineYellow 107A | Acid Yellow 250 |
|
| WFA Sun Yellow 119 | Acid Yellow 19 |
|
| WFA Golden Yellow 199c | Acid Yellow 199 |
|
| WFA Bright Orange 233 | Acid Orange 156 | From MSDS |
| WFA Red 338 | Acid Red 138 |
|
| WFA Fuschia 349 | Acid Red 249 | Not a Nylomine. |
| WFA Bright Red | Acid Red 151 |
|
| WFA Red 366 | Acid Red 266 |
|
| WFA Rhodamine Red 370 | Acid Red 52 | Not a Nylomine |
| WFA Polar Red 390 | Acid Red 131 | Not a Nylomine |
| WFA Navy 413 | Acid Blue 113 |
|
| WFA National Blue 425c | Acid Blue25 |
|
| WFA Blue 440 | Acid Blue 40 |
|
| WFA Turquoise 478 | Acid Blue 185 |
|
| WFA Brilliant Blue 490 | Acid Blue 90 | Not a Nylomine |
| WFA Black 672 | Acid Black 194 |
|
| WFA Green 725 | Acid Green 25 |
|
| WFA Green 728 | Acid Green 28 |
|
| WFA Brilliant Violet 817 | Acid Violet 48 |
|
The dyes that are not Nylomines are Ricoamides. The Nylomines and Ricoamindes share many of the same dyes.
Water
Most municipal water is chlorinated. Chlorine is a bleach and will effect the dye color. The amount in the water varies wildly from day to day. Your water may be hard and it might contain heavy metals. Your municipal water supplier can give you an analysis of the water. They are required by law to have this information available. As a dyer, you want to know if the water hard, how hard it is, and whether it contains interfering heavy-metal ions like iron and copper. This will tell you about the quality of the water as it goes into the water distribution system; however, it may flow from your faucet with things it picked up in the water pipes--commonly rust (iron) and copper and, in a few unfortunate cases, lead. The municipal analysis is a starting place. A dye bath is mostly water, probably 99 percent, so the quality of the water determines the quality of the dyeing. It is also the most invisible or neglected dye bath ingredient.
Very simple tests for determining water quality are available from laboratory or swimming pool supply houses. They come in a jar with instructions and involve a strip or stick that you dip in the water. The strip has a colored reactive section that changes color in response to the contaminate. You match the color to a chart to determine the hardness or iron concentration. These can be useful to help you determine the quality of your water as it comes out of the tap.
[#23]
To compensate for hard water, add sodium hexametaphosphate to the dye bath or use softened water. Both these methods will also take care of any heavy metals in the water. The chlorine content is a more difficult issue, and many people just dye with it. A lot of the chlorine is lost in the water heater. There is a anti-chlor chemical, but I have never used it. I do have a carbon polishing filter that removes chlorine for dye bath water.
Safety Considerations
The two major hazards I encounter in my work are inhaling the very finely powdered dyestuffs and fumes from discharge procedures. Make sure you have good ventilation. Dust and fumes can circulate in a home and affect people in other rooms.
Any tiny particle that gets deep into your lungs can cause damage. Wear a particle or dust mask, available at any hardware store, when working with dye powders. Make sure it fits well. When doing discharge procedures, wear a respirator with acid gas cartridges.
A clean studio is a healthy studio. Spilled dye will dry into powder and find its way into your lungs. Wipe up any spills with water.
Some people develop allergies to certain dyes after exposure to them. The best way to deal with these allergies is to prevent them. Do not let any dye enter your body. Don’t eat it, don’t breathe it, don’t absorb it through your skin. In addition to the mask and respirator already mentioned, wear gloves when working with dye baths or wet dye on fabric. Consider wearing a plastic apron (especially if you are sloppy, like me!). Never use the same equipment for both dyeing and food preparation.
The best way to dispose of dye baths is the sewer system--it is designed for waste disposal. The amount of waste from home dyeing is insignificant in the total waste treated, even in a small village. If you work outside, you may have to carry the spent dye bath to the toilet for disposal.
GLOSSARY
ACIDS
for use in acid dye baths
Sulfuric acid, H2SO4. A strong acid. used for pH<3.5. A clear, colorless, odorless liquid.
Acetic acid, CH3COOH. A weak acid. Used for pH 3.5-5.5. Acetic acid is a liquid that has a recognizable pungent odor. Vinegar is about 5% acetic acid with a pH 2.4-3.4. It can be purchased as 26% solution from shops that sell chemicals for developing photographs (sometimes it also contains a yellow colorant that renders it unsuitable for dyeing), or as a 56% solution from some dye suppliers (this must be shipped as a hazardous material and the shipping is thus expensive) and as glacial acetic acid (99.5%) from chemical suppliers (the name glacial comes from the fact that at slightly below room temperature it solidifies or freezes). . Acetic acid and sodium acetate form a buffer system that maintains the pH constant around pH 4.7.
Citric Acid, HOC(CH2COOH)2COOH. A weak acid but stronger than acetic acid. It is a white crystalline solid at room temperature. Widely occuring in plant and animal tissues, responsible for the pleasant sour taste of citric fruits. Easy to buy (used in the kitchen) and ship. Can fom a buffer with sodium citrate but this buffers works best around pH 3.1.
Acid salts
Ammonium sulfate, (NH4)2SO4. A salt that is a white crystalline solid.
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