Direct dyes are a class of hot water dyes for use on cellulose fibers, such as cotton. It is one of the two types of dyes that are mixed in 'all purpose dyes' such as Rit, Tintex Hot Water dye, and Dylon Multi-purpose Dye. (The other type in the mixture is an acid dye, which will not stay in any cellulose fiber for long.) Try to find them pure, without the useless (for cotton) and money-wasting acid dyes mixed into the 'all-purpose' dyes.
In most cases, better results will be obtained, often with versatile and easier-to-use cool water methods, if you use fiber reactive dye instead of direct dye. However, there are some cases in which direct dye is preferred.
The colors of most direct dyes tend to be duller than those provided by fiber reactive dyes, especially after fading in the laundry. The washfastness of direct dyes is poor: expect anything dyed with them to 'bleed' forever. They lack the permanence of the cold water fiber reactive dyes which most hand-dyers prefer for use on cellulose fibers. As a result, clothing dyed with direct dyes should be laundered in cool water only, with closely similar colors. The washfastness problem can be reduced by following dyeing with the use of a cationic after-treatment such as Retayne.
The main reason why direct dyes are used is because of cost. Although the widely available all-purpose dyes which contain a mixture of direct and acid dyes are very expensive, per pound of fabric to be dyed, direct dyes sold alone and purchased in bulk are among the cheapest of all dyes.
Direct dyes are applied in hot water, typically between 175°F and 200°F. They can be applied in the same boiling-water dyebath with acid dyes (whether for same-color effects, as in all-purpose dyes, or contrasting effects, as in the case of AlterEgo brand dyes).
Direct Dyes are used on cellulose fibers such as cotton, rayon, and linen, but they will also color silk and wool unless dyeing is accompanied by a chemical 'reserving agent', which unfortunately is unavailable to home dyers (except, perhaps, as an element in Alter Ego's very expensive proprietary 'fixative').
Direct dyes are not generally more lightfast than fiber reactive dyes; many direct dyes are less resistant to light than similarly-hued fiber reactive dyes, and both tend to be less lightfast than vat dyes. There are just a few cases in which a particular direct dye may be more lightfast than similar shades of fiber reactive dyes (see About Lightfastness). For example, Colour Index Direct Orange 39 and Direct Blue 86 are quite reasonably lightfast, with a rating of 6 (on a scale of 1 to 8). While some fiber reactive oranges are as lightfast, not all are; the popular Colour Index Reactive Orange 4 rates only 4 on that scale, while the Turquoise Reactive Blue 140 rates 5-6 on that scale.
Unfortunately, the cationic dye fixatives, such as Retayne, that are required to render the washfastness of direct dyes acceptable also reduce lightfastness somewhat.
Direct dyes are only loosely associated with the fiber molecule through the property called substantivity, which is the tendency of the dye to associate with the dye without strong bonds. This substantivity is increased by increasing the size of the dye molecule, so direct dyes tend to be large. Small dye molecules tend to be bright, while large dye molecules tend to be duller (as there are more parts that can absorb additional wavelengths of light), so direct dyes are generally much less bright in color than fiber reactive dyes. Substantivity is said to result from a combination of the relatively weak Van der Waals forces and some hydrogen bonding.
Dharma's Industrial dyes are eight different colors of direct dyes—"not as washfast or as bright as our other dyes, but easy & cheap". They are very inexpensive to use, costing as little as 6 cents per pound of fabric to be dyed. A pound of Dharma's Industrial Dye costs only $6.
PRO Chemical & Dye until recently sold an inexpensive line of nine different direct dye colors under the name "Diazol Direct Dyes". Dyeing one pound of fabric to a medium shade requires only 2.25 grams of dye, less than is required for most dye types. This means that a pound of dye would be sufficient to dye more than 200 pounds of cotton fabric. See their instructions for Immersion Dyeing using Diazol Direct Dyes. The different colors have different costs, with prices being set lower for the less expensive dyes, rather than all being set to the same price as the most expensive color, as in many brands. ProChem was unusual among hand-dyers' suppliers in being upfront about which dyes are included, which allows you to learn much more about what materials you are using.
Aljo Mfg. sells the same direct dyes that ProChem used to, by Color Index Number, as well as blended colors. They may supply their dyes in a different strength, but you can ask for 100% of standard strength.
Jacquard Products has introduced a line of direct dyes called iDye, to go with their line of low-energy disperse dyes called iDye Poly. The two kinds of dyes may be mixed in order to dye cotton/polyester blends in a single dyebath. Although instructions are included for dyeing with iDye in the washing machine, dyeing polyester or blends with iDye Poly requires boiling on the stovetop. iDye is much more expensive per use than Industrial Dyes or Diazol Direct Dyes, as it is packaged in individual-use packets like Rit or Tintex all-purpose dye. Each 14-gram iDye packet will dye 2 to 3 pounds of fabric, at a cost between $3 and $4. Specific identities of the individual dyes used in iDye are unknown to this writer, and the manufacturer reports that all of them are proprietary blends; thus, data for lightfastness and washfastness are not available and require testing by the individual user. Two noteworthy members of the iDye line are a fluorescent yellow, which will appear to glow under sunlight or a blacklight, and a Sun Blocker, whose main ingredient is identical to that found in Rit Sun Guard (we have found Rit Sun Guard to be quite effective in turning clothing into a strong sunscreen).
Cushing sells a line containing many different pre-mixed colors of direct dyes; no information is available on which direct dyes are included. There are two groups of primary colors: the lighter set is Scarlet, Light Blue or Copenhagen Blue, and Yellow, while the darker would be Blue, Cardinal and Canary. They are designed to be used directly, however, not for color mixing; thus, there are forty different colors available. Half an ounce of Cushing Direct Dye is sufficient to dye two pounds of cellulose fiber, such as cotton, and costs $3.65. You can order directly from the WCushing website or from some dye suppliers such as Earth Guild.
Rit brand's Proline Bulk Dye consists of only direct dye, with no acid dye included, but apparently with a considerable amount of salt included, so a given weight of dye will not go nearly as far as with ProChem's Diazol Direct dyes or Dharma's Industrial dyes. See the Rit Dye website for bulk purchases. One pound, enough to dye sixteen pounds of fabric, costs $14.
Direct dyes are also found, along with leveling acid dyes, in all all-purpose dyes, such as Rit® brand dye, Dylon® Multi-purpose dye (not to be confused with Dylon®'s fiber reactive dyes, in their Cold Water and Washing Machine lines of dye), DEKA L® Hot Water Dye, and Tintex® Easy Fabric Dye.
There are a few natural dyes which fall in the category of direct dyes. These include turmeric, saffron, and walnut. Unlike most other natural dyes, these dyes do not require the use of a mordant. Turmeric and saffron are known for being fugitive, that is, they are not very fast to either light or washing. Turmeric in particular is said to require redying every year or so.
The hazardous carcinogenic direct dyes that are based on benzidine are no longer allowed to be used in direct dyes or dye mixtures sold in the United States. They were, however, sold in the US in all-purpose dyes before and throughout the 1970s. Benzidine-based direct dyes are still used industrially in some countries, but their use should be strictly avoided. The specific dyes to avoid are direct black 1, direct red 28, direct black 38, direct blue 6, direct green 6, direct brown 95, direct brown 2, direct blue 2, and direct black 4. More information on this issue is included near the bottom of my page on all-purpose dyes. See the US government document, Health Hazard Alert--Benzidine-, o-Tolidine-, and o-Dianisidine- Based Dyes.
Some o-dianisidine-based direct dyes are still being sold for household use in the US, in the form of dye-impregnated tie-dye color cords, and may be sold in other forms in other countries. They are still available for industrial use in the US and elsewhere. Be sure to request an MSDS from your dye supplier for each direct dye that you use, and avoid all dyes that are based on benzidine or o-dianisidine. Dyes that are made from these chemicals may break down to form them again, after they are absorbed into the body, so they are not safe to be exposed to. Both benzidine and o-dianisidine are suspected cancer-causing chemicals. A careful adult who understands safety precautions can probably use these dyes safely, but they should never be given to children to use, since children are less likely to follow all safety rules.
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