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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