Category Archives: dyeing silk

Once thin silk takes one color of dye can it be overdyed a darker color?

I recently dyed some pieces of silk and gauze. Once the silk takes one color of dye can it be overdyed a darker color? The colors I got were not what I expected. In one a green color took over the piece. I have tried over dying the green with cobalt and it’s not doing anything. I would love any advice you have to offer.

Thin silk is limited, as you’ve seen, in how many dye molecules it can take up. While thicker fabrics such as a heavy raw silk, or the cotton jersey of t-shirts, can add more color through six or more rounds of dyeing, a very thin sheer fabric, such as chiffon or gauze, may do so through only one or two rounds of dyeing, refusing to change color further when you dye it again.

Physical manipulation of the fabric, as by rough washing, can free up more dye sites in a fabric, but that’s not a good idea with fine silks.

Removing the dye color with a dye discharge chemical, such as thiox, will probably not help, because the dye molecules will still be bound to the fabric even after they have been decolorized by the reducing agent. The hypochlorite in chlorine bleach might chew up enough of the surface of the fabric to reveal more dye sites, if you’re dyeing cotton gauze, but you should never use chlorine bleach on silk, since it is very destructive to protein fibers.

You might be able to add another layer of color if you use an entirely different class of dye which attaches to the molecules of the fabric in a different way. For example, if you have been dyeing your silk with Procion dyes plus soda ash, you might find that dyeing them with acid dye plus an acid, such as vinegar, will allow one more round of color—or if you’ve been using acid dyes, which includes Procion dyes that have been set with an acid rather than soda ash, then you might try dyeing with Procion or another fiber reactive dye, and setting it with soda ash. Definitely a matter of trial and error, no guarantees that it will work, but it is worth experimenting.

Also see my earlier post, “Will a fabric reach a saturation point after which it cannot take any more dye, or any more dye of a given colour?“.

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Can I use vinyl sulphone as an acid dye on silk with citric acid for immersion dyeing?

Name: Nancy
Country or region: northeastern USA
Message: Can I use vinyl sulphone as an acid dye on silk using 1 TBL citric acid when immersion dyeing in 3.5 gallons of water? Slowly heating to 185°F and holding for 60 minutes, then slowly cooling.

Yes, this looks like a recipe that should work. You might want to use more citric acid, though.

Oddly, in this recipe, a vinyl sulfone dye may act as a true fiber reactive dye on silk, unlike other types of fiber reactive dyes, which act only as acid dyes when applied at acid pHs. You might get a combination of acid-dye-type bonding and fiber-reactive-type bonding.

PRO Chemical and Dye provides a similar recipe for immersion dyeing wool with vinyl sulfone dyes, combining 2.5 gallons of water with two tablespoons (or 35 grams) of citric acid, and simmering (about 185 degrees F, or 85 degrees C) for between 30 and 60 minutes. You’re using more water and less citric acid than their recipe. Their recipes for immersion dyeing silk with these same dyes calls for a high pH, instead, with sodium carbonate or potassium carbonate instead of the acid, but, since it is a protein fiber, silk can also accept dye using recipes intended for wool. Dyeing silk at a low (acidic) pH will tend to preserve its luster and stiffness better than dyeing it at a high (basic) pH.

The difference between acting as an acid dye and acting as a fiber reactive dye lies in how the dye becomes attaches to the fiber. An acid dye is attached to a protein fiber by means of a combination of hydrogen bonding and salt linkages. A fiber reactive dye, in contrast, is attached by a true covalent chemical bond, making the dye and fiber molecules into a single molecule, firmly bound together. The advantage of the fiber reactive type of bond is that is it much more permanent, and cannot be washed out with hot water, unlike acid dyes. See “What kinds of chemical bonds attach dyes to fibers?”.

The vinyl sulfone dyes, also known as Remazol dyes after the brand name under which they were first introduced, contain a masking group of atoms in the dye molecule; this masking group prevents the dye from reacting with the dye water, thus giving the dyes a longer life when dissolved in water, and its slow removal in a hot dyebath helps wool to dye more levelly (producing a more perfectly solid color) than it would if all of the dye were immediately able to react with the wool. There are two different ways to remove the masking group: one, which works very quickly and without high heat, is to produce a high pH with a chemical such as sodium carbonate (soda ash). Surprisingly, the other is to heat the dye in the presence of a mild acid, such as citric acid. The ideal pH for the removal of the masking group is between 5 and 6, which is only mildly acid. This takes some time, but an hour should be plenty of time for it.

Typical hand-dyeing recipes for using fiber reactive dyes as acid dyes call for producing a somewhat lower pH than is required for milling acid dyes or fast acid dyes. ProChem’s recipe’s 35 grams of citric acid in 2.5 gallons of water, or 10 liters, works out to 0.35%, while your recipe of approximately 17.5 grams of citric acid in 3.5 gallons of water, or 14 liters, is 0.125%. It would be good to check the pH of this amount of citric acid in the amount of the water you are using, and keep a record of it. (See “How do you use citric acid as an auxiliary chemical for dyeing?”.)

A note on spelling, for anyone curious as to why sometimes “sulfone” appears spelled with a “ph”, and sometimes with an “f”….The main reason why we see the spelling “vinyl sulphone” is that Jacquard Products sells a brand of vinyl sulfone dyes which they name “Vinyl Sulphon”, the intentionally odd spelling, along with the capital letters, serving to distinguish it from the generic name for the vinyl sulfone dyes. The generic name is sulfone, rather than sulphone, as decreed by IUPAC, the international federation of chemists which sets standards in chemistry nomenclature; a sulfone is a chemical compound containing a sulfonyl functional group (a sulfur attached with double bonds to two oxygen atoms), in which the sulfur is also attached to two carbon atoms. The element sulfur was often spelled “sulphur” in British writings starting in the eighteenth century and continuing until 2000, when the Royal Society of Chemists in Britain agreed to standardize to the IUPAC spelling; interestingly, sulfur had been the original spelling even in British usage. The letter combination “ph” typically indicates that a word was originally sourced from Greek, but the origin of the word “sulfur” is Arabic, not Greek.

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questions about silk dye safety

Name: Anna
Country or region: France
Message: Hello,
Thank you for your website and all the information that it provides. You are offering the world with a wonderful service. If you wouldn’t mind, I would love to have your opinion on a few inquiries.

My mother has her brand of silk clothing that she has always dyed herself, and ever since childhood my family has been exposed to various types of fumes, including those from dyes (mostly acid dyes from the polish brand Kakadu, if this rings any bells ) but also fumes from steaming screen-printed silk, which always produces an awful smell and always felt to me like this could not be a good thing to be breathing near. So I guess my question is, what could be the risk of exposure to such fumes ? Is there any literature and studies that may enlighten me on the matter? I personally am experiencing a tightness in the chest area since spending a few months with my mother, and it raised my concerns regarding my health as well as my mother’s and her employees.

It’s difficult to talk about the risks of fume exposure without knowing what kinds of dyes and other chemicals have been used. I can’t find any information on the Kakadu brand of textile dyes. It would be helpful if you can request MSDS (Materials Safety Data Sheet) information from the seller for each of these dyes, but even that will tell us nothing about what dyes and other chemicals may have been contained in older, now discontinued, formulations of the same brand of dyes. (See, for instance, the question “Did Sennelier Tinfix Silk Dyes cause my wife’s hyperthyroidism?“, in my old dye Q&A blog, for a case in which it was impossible to find MSDS information for a discontinued dye formula.)

The tightness in your chest might be due to asthma caused by an allergy to the dyes. Asthma is a known occupational hazard for workers in the textile dye industry. This is normally an issue only with powdered dyes, as dyes are less likely to get into the air while they are dissolved in water. Experience with my relatives with Chronic Obstructive Pulmonary Disease (though they did not work with dyes) makes me worry about actual lung damage from exposure to unsafe chemicals, though I don’t know of any particular relationship between COPD and the sort of exposures you report. I would encourage anyone suffering from tightness in the chest to see a doctor. A spirometer can be used to test your lung function.

Once a person has a demonstrated allergy to a particular type of dye, that person should stop using that type of dye at all, and switch to other types of dye. For example, one well-known quilt artist developed an allergy to Procion MX dyes and had to switch to the very similar Cibacron F dyes (now known as Novacron F dyes). Continued exposure to a substance to which one is badly allergic can result in a serious case of asthma.

Do you, yourself, take particular precautions when exposed to fumes, whether it is by adding ventilators, air purifiers, plants to your environment or special diet or supplements to keep you from storing toxic compounds in your soft tissues ?
I remember reading an article a few years back about the use of algae and chlorophyle in general as well as the use of glutathione supplements to protect workers from air born toxins in the denim industry, but I can’t seem to find anything on the subject as I am looking today.

As a rule, I don’t believe in nutritional supplements to counter toxic exposures. There have been many, many cases in which useless substances are promoted for this purpose solely for the enrichment of the those selling them. The supplements I have seen being promoted for this purpose are generally nothing more than useless scams. Neither algae nor chlorophyll is likely to have any beneficial effect. Glutathione, if given in time, is an effective antidote for overdoses of acetaminophen (whose other generic name is paracetamol), and has other medical uses, but again I would not rely on it to counter unspecified toxins. [Correction: N-acetyl cysteine is the antidote to acetaminophen/paracetamol poisoning, used for its ability to increase the body’s levels of glutathione. Glutathione itself is subject to breakdown in the process of digestion.] In general, dietary intake of antioxidants in food, particularly in colorful vegetables and fruits, is helpful (for example, there are scientific studies suggesting that eating curry may be good for lung function in COPD, because of the antioxidants found in turmeric), but, again and again, the isolated nutrients have proven useless when given in the form of dietary supplements.

I do take precautions when dyeing, and it is important for all dyers to do similarly. The first step is to avoid breathing the dust generated by handling dye powders. This is the most common hazard in handling dyes, as even non-toxic dyes, like many other powders, are capable of producing severe allergies and asthma if repeatedly inhaled. A dust mask is usually sufficient, but only if it fits so well that no air comes in around the sides of the mask. All air that is breathed must come directly through the filter material of the mask in order for it to provide protection.

Of course it is unwise to eat any dye that has not been cleared as being safe for human consumption. This means that hands must be protected with waterproof gloves, and washed before eating or smoking. This sounds obvious, but I have many times seen artists eat a sandwich or smoke a cigarette with unwashed hands covered in  oil paints whose pigments were known to be very toxic, such as cadmium red and chrome orange! While most of the dyes we use are  unable to penetrate a waterproof glove without any holes, and in most cases of glove punctures stay in the outer layers of skin rather than penetrating inside the body, sometimes basic dyes (also known as cationic dyes) have been used like acid dyes, or even sold as one or two of the colors in a line of acid dyes. Basic dyes are, in general, more dangerous than acid dyes or fiber reactive dyes, because, unlike these other dye classes, basic dyes have a positive electric charge that encourages them to cling to and penetrate skin.

When handling small quantities of objectionable solvents, such as the alcohol used to dilute some silk paints, a dust mask is of no use at all. Make sure to have good ventilation. A good way to improve ventilation in your work area is to use electric fans in two windows, one on each side of the work area, with one fan pushing air outside through one window, while the other fan sucks air inside through the other window. Cross ventilation is much more effective than a single open window.

Larger quantities of dangerous solvents require more precautions, not instead of, but in addition to, having excellent flow-through ventilation. It is important that the amount of a solvent or other chemical in the air be no greater than the safe vapor concentration for that chemical, which you may be able to find in the MSDS safety information for that substance. Any significant exposure to chlorine bleach, for example, calls for a well-fitting respirator (not merely a dust mask) with an acid gas cartridge. Different toxic substances require different kinds of cartridges. Some solvents, such as alcohol in fabric paints, or the volatile solvents used to dissolve gutta in resists in silk painting or for dry-cleaning, cannot be adequately screened out by a respirator.

I myself purchased an extra stove burner specifically for use out-of-doors when dyeing polyester, because the carrier chemicals used with polyester dyes are unhealthy to breathe (and smell horrible). Boiling these chemicals indoors would have permeated the entire living area; it’s impractical to outfit everyone in the house with a proper respirator, and unpleasant to wear one for more than a few minutes anyway. When working in a lab, I would use a fume hood to work with similarly noxious chemicals.

Also, do you have the knowledge of any association that could provide specific guidelines for the work place environment and safety when it comes to silk dying and screen-printing ? My wish is to really do all that is in my power to protect those around me and offer a pleasant work environment.

PRO Chemical & Dye’s Studio Safety Guidelines are good, though brief.

Although it is not a new book, I very much liked the information on setting up a safe dye studio in Deborah M. Dryden’s book, Fabric Painting and Dyeing for the Theatre. Probably the best book for me to recommend to you would be Monona Rossol’s 2001 book, The Artist’s Complete Health and Safety Guide. Both of these books identify specific hazardous dyes that should be avoided altogether, since there are safer alternatives. Most of the dyes in question are direct dyes, while a few are acid dyes; none are fiber reactive dyes.

Dye sellers who mix different dyes together to make different colors will probably not reveal which specific dyes are in a given dye color, as this is a trade secret, but they should provide information for all of the dyes that they use in their mixtures in any particular line of dyes. Any company that sells dyes should provide MSDS information so that you will know whether to be more concerned about the safety of their dyes.

Dyes based on benzidine, o-toluidine, or o-dianisidine are dangerous, because, after being absorbed by the body, they can be metabolized back to the carcinogenic chemical they were made from. Benzidine is the compound of greatest concern. In order to know for certain whether any of your dyes present this hazard, you have to have the MSDS page for each dye. With some types of dyes, it is not difficult to get this information, so you can feel safe from these chemicals. With dyes whose manufacturers do not identify the dye chemicals or make MSDS information available, there is no way to tell.  Until the early 1980s, these dyes were in common use, without warning labels. The dyes are listed Rossol’s book and in a US Government publication from 1980, “Health Hazard Alert–Benzidine-, o-Tolidine-, and o-Dianisidine- Based Dyes“, which can be found in the Internet Archive.

The main hazard from serious exposures to benzidine, o-toluidine, or o-dianisidine is an increase in the risk of bladder cancer. Once someone has been exposed to these chemicals, the most important single precaution to take is to avoid tobacco smoke, since previous exposure to chemicals that cause bladder cancer increases sensitivity to future exposures, and tobacco smoke is a major cause of bladder cancer.

A paper on the University of Illinois at Chicago website, Silk Screen Printing, written by Ronald Fuchs and Michael McCann about the dangers of silk screen printing, focuses on the hazards of solvents for fabric printing inks, such as toluene, and advocates the use of water-based inks, instead. The screen-printing inks, which are based on pigments rather than dyes, are different from dyes used for printing silk fabrics, as the dyes used on silk are water-based.

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