There are two kinds of natural dyes: substantive and adjective.
SUBSTANTIVE dyes, these include the tannic acid from gall nuts, walnut leaves, turmeric, as well as alizarin reds from annatto, cochineal, and safflower, indigo and the purple of some mollusks. They need no mordants to help them adhere to the fiber. The use of a mordant enhances and can modify these colors.
ADJECTIVE dyes do. The mordant joins with the fiber and the dye to set the color permanently.
A mordant or dye fixative is a substance used to set or bind the dye or colorant on fabrics by forming a bond with the dye, which then attaches to the fabric or fiber. It is used for dyeing fabrics or for intensifying the color of the dye
Aluminum is the most commonly used mordant. It is inexpensive and relatively safe to use and produce the purest color from the dye. They are used all around the world.
There are several different types of aluminum mordants. Each aluminum salt contains different amount of aluminum. For instance, only three – quarters the amount of aluminum sulphate is required to achieve the same performance of PAS (potassium aluminum sulphate dodecahydrate (alum). The quantity required of each can be calculated by using the molecular weights of each mordant.
Potassium aluminum sulphate dodecahydrate
PAS is the most widely available mordant. It is used to mordant protein fibers and is also used to make neutral aluminum acetate when combined with soda ash solution. It becomes a mordant for cellulose. Alum was traditionally mined as a ground mineral; it can still be found naturally in some locations but most alum is now industrially produced.
Can be used to mordant protein fibers, it is readily available and inexpensive. It contains more aluminum than PAS.
Ammonium Aluminum Sulphate
Can be used to mordant protein fibers, it is expensive that the other two and found in small quantity at a grocery store.
Potassium aluminum sulphate
Is a water -free alum, also known as calcinated or burnt alum, it is commonly used in Japan and is stronger but harder to dissolve than PAS.
Is an aluminum salt of acetic acid. It is a mordant for cellulose. It is primarily used for printing, but is also applied as a mordant. It can be used on silk too, but the less expensive PAS is equally effective.
- Neutral aluminum acetate or aluminum triacetate
- Monobasic aluminum acetate also known as aluminum diacetate
- Dibasic aluminum acetate or basic aluminum monoacetae
All three forms of AA work equally well.
Aluminum from Plants
Some plants that grow in soul with high concentration of aluminum are capable of absorbing the aluminum through their roots. These plants are called hyperaccumulators include tea, camellia, club moss, and symplocos and many others. When the aluminum in the plant is enough it can be extracted by boiling in water with the textiles to mordant it. The Bebali foundation. In collaboration with Michael Garcia, has done significant research in the symplicos plant leaves used by the Indonesian dyers.
Iron salts are used as mordants to sadden or darken colors. Iron will shift a yellow dye toward green and a pink dye towards purple. If combined with tannin it produces a gray or black. Small amount of improve the lightfastness of dyes. Usually 1-2% iron to WOF is enough, higher concentration of iron leaves the fabric stiffer and more susceptible to deterioration.
Is the most common form of iron for the dyer. When iron is present in a textile, the damage caused to the fiber by oxygen and UV light is accelerated. When dissolved Ferrous Sulphate generates some sulfuric acid when dissolved, which is harmful to any textile.
Ferrous sulphate is not recommended for silk, since silk is more sensitive to UV light than either wool or cellulose.
Iron (Ferrous Acetate) is an iron salt of acetic acid it is used mainly for printing but can be used as a post dye treatment to sadden the color. Ferrous acetate is not readily available and it has a short shelf life
It can be made by combining sodium acetate with ferrous sulphate or soaking rusty nails in vinegar.
Copper sulphate is a metal salt that used as a post mordant but sometimes used a pre- mordant, copper saddens the color and turns it to a greenish tone, it also improves light fastness. Copper requires care in handling and disposal. The safest and only recommended was is to use copper or brass pots or adding a piece of metal into the dye bath.
Copper sulphate also known as Blue vitriol is a good mordant if one wants to add greenish tones to the colors. It works well for wool, fair to good for silk and some vegetable fibers.
Mordanting animal fibers with Copper sulphate: for one pound of animal fiber, you need 3 gallons of warm water, 2-0unces of copper sulphate dissolved completely. Add the wet scoured fiber and simmer for an hour.
For mordanting vegetable fibers with copper sulphate for one pound of fiber take 3 gallons of warm water and 3-4 ounces of copper sulphate.
Stannous chloride us a metal salt that will brighten some dye colors on protein fibers esp. cochineal the hue can shift to scarlet red. It brightens the yellows and turns madder to a brilliant orange. Traditionally, tin was directly added to the dye bath but it can also be used as a pre- mordant instead of PAS. Tin was not used in natural dyeing until the 17th century. It is expensive and can damage the fiber it should be used only to achieve special effects and should be mixed with cream of tart to moderate the acidity and keep the fiber soft.
Mordanting animal fibers and soft vegetable fibers with tin.
One pound of dry fibers, you need 3 gallons of water. Two teaspoons of Tin dissolved. Prewet fiber is added and cooked for an hour, covered and let it cool, rinse dry or dye.
Tin is used to brighten color after they have been dyed, yarns that have been dyed with other mordants maybe brightened with tin. To do this you need 3 gallons of warm water for one pound of dry yarn and one teaspoon of tin well dissolved. Simmer the wet dyed yarn for 15-30 mins in this solution, remove the fiber and wash it once with mild soap while it is still hot/warm.
Chemical described as mordant assist are used to change the chemical structure of the mordant and to modify the pH or to help fic the mordant on to the fabric.
Cream of Tartar
Or potassium tartrate is an acid salt that helps modify the pH by lowering it slightly for wool fibers and heated mordant bath can be harsh on the wool and pH adjustment helps protect the wool during mordanting and gives a better hand. It also slows down the absorption of the mordant on wool as well as a leveling agent and resulting in more even dyeing.
Cream of tartar is not used when mordanting silk, silk is mordanted without heat and dyed at a lower temperature so as it might damage the fibers, additionally silk does not have the same tolerance for acidity as wool. The increase acidity from Cream of Tartar would slow down the absorption of mordants too much and less of the mordant will be able to attach.
Traditionally cow dung was used to neutralize and fix mordants onto cellulose fibers when tannins were not applied prior to the mordant. The phosphate and enzymes in the dried dung are the active ingredients. These enzymes are useful in removing gum thickeners used in printing. Chalk or calcium carbonate is now used instead.
Tannin has an affinity for all fibers, it has more affinity for cellulose and is an important component for mordanting cellulose fibers for immersion dyeing.
Sodium Carbonate (Soda Ash) Can also be used to raise pH.
Color fastness and dye lot leveling:
Bleeding and crocking are eliminated by using Glauber’s salt in the dye bath. Glauber’s salt is a lot used to level the dye bath. One quart of hot water to each pound of dry fiber. Dissolved Glauber’s salts to the warm water which is enough to cover the batch if fiber at the wet fiber to this bath and simmer 30 mins to an hour. Note this dulls the color. Rinse and dry the fiber.