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Natural Dyes Basics
There are many plants and chemicals in nature that can dye fabric, leather, hair, and other items. Humans started using dyes as soon as they were discovered; 6000 BC or earlier. In the Medieval period there were certain plants that were heavily relied on for most colors.
Section 1: Safety
Because dyeing substances and mordants can be poisonous, there are some important rules to follow when dyeing:
Disposing of Mordants and Dyes:
Always dilute baths before pouring them out. Mordant baths and extremely acidic or alkaline baths should be diluted heavily before disposal. Natural dyes from plants can usually be poured out onto the ground without ill effects on surrounding vegetation, but mordants and very alkaline or acidic water can damage plants. Never pour baths into ponds or running water, pour them as far away as possible from wells and septic systems, and try to avoid gardens, valued plants and compost heaps. The exception would be if your bath contains something you would have added to the soil anyway; i.e. a bath of lime and madder (no mordants) could be poured out onto acidic soil.
Pouring dyebaths and mordants down the drain can cause problems for septic systems, especially when the bath is extremely acidic or alkaline and when the bath contains a lot of loose fibers or solid dye material. People on public water sewer systems should check with their local municipality to find out if there are restrictions on what chemicals can be disposed of down the drain. In most cases, dyeing occasionally will not cause a problem for the local sewer, but large-scale or frequent disposal of mordants and dyebaths could damage their systems.
Section 2: Dyeing Terminology
Some things will give bright colors to fabric that are not permanent, like beets, grass, and berries. These are considered stains rather than dyes because the bright colors quickly fade to yellow or brown shades.
Substantive vs. Reactive:
Dyes can be substantive or reactive. Substantive dyes stick to the surface of the fiber and eventually wear off. Blue jeans are dyed with indigo, a substantive dye, and so they fade in areas of stress (like your knees). Reactive dyes make chemical bonds with the fibers and will not wear off as easily. Most dyes are reactive.
Reactive dyes work best with a mordant. A mordant is a chemical (usually a metal) that helps the dye bond chemically to the fiber. Examples of metallic mordants are aluminum (alum), copper, tin, iron and chrome. Some non-metallic mordants are cream of tartar and tannins. You can sometimes get the advantage of a mordant by using solid pieces (i.e. throw copper pennies or iron nails in a dye vat), but serious dyers usually buy powdered forms of the metals. WARNING!! MANY MORDANTS ARE POISONOUS and should not be inhaled or eaten!!!
Adjective dyes are dyes that change color depending on the mordant. Most reactive dyes are also adjective dyes.
Pre-mordanting is the process of soaking the fibers in a mordant bath before entering them into the dyebath. Pre-mordanting can be done immediately before dyeing or the fibers can be allowed to dry completely in between mordanting and dyeing.
Bancroft was an 18th Century chemist who theorized and tested the simultaneous mordanting and dyeing of fibers. Some dyes work well with Bancroft's method, while others get much better results from pre-mordanting and dyeing as separate procedures. While the technique is often called "Bancroft's", it was not actually new and was used during the Medieval period.
Post-mordanting is done by dipping the fibers in a mordant bath after dyeing. This bath is sometimes called a "Modifier".
Any bath used after the main dyeing process to change the color. It may contain a mordant or may be very acidic or alkaline.
The pH of a liquid can be taken using litmus paper and is usually expressed on a scale of 0-14 with 7 being "neutral". Numbers less than 7 are acidic and numbers greater than 7 are alkaline (or basic). In chemical terms, the more loose hydrogen atoms in a solution, the more acidic it is. Some dyes and fibers dye differently at different pH levels.
Plants containing indigotin (Indigo, Woad, etc.) work as "vat dyes" where an anaerobic environment must be achieved in the dye bath before the dye will adhere to fibers. Such vats are usually kept at a steady, warm temperature to promote optimal vat culture.
Overdyeing is the process of taking fiber already dyed in one dyestuff and dyeing it with something else. It can often produce much better colors than dying with one dyestuff alone. For instance, dyeing a fiber yellow and then overdyeing with blue can achieve beautiful greens. Historically overdyeing was often used commercially to take advantage of two dyestuffs in the same color range with different properties; i.e. brazilwood produces a really bright red that fades, and madder produces a very long-lasting red (but madder red isn't always as bright), so the two were often used together.
Section 3: Natural Dyeing Principles
Animals are Acidic and Botanicals are Basic:
Animal proteins, like wool, other hair, and silk dye best in acidic conditions and are weakened by alkalines. If you dye an animal protein in alkaline conditions, it is best to end with a diluted vinegar rinse to restore a slightly acidic pH to the fibers before they dry.
Botanicals, or plant materials like cotton, flax, hemp, ramie, etc., dye best in alkaline (basic) conditions and are weakened by acids. If you dye a botanical in acidic conditions, it is best to end with a weak washing soda bath to restore the fibers to slightly alkaline before they dry.
Measuring Mordants and Dyestuffs:
Most dyeing recipes specify ingredients by weight rather than measure. Recipes will also specify the amount of fiber to be dyed OR the other ingredients will be expressed as a ratio to fiber weight. This is because the amount of water in the dyebath will not affect how strongly the fiber takes color, but the amount of dyestuff in the dyebath does. So if you dyed one ounce of fiber with one ounce of dyestuff and want to reproduce the same color on 5 more ounces of fiber, multiply the amount of dyestuff times 5 also. The water should always be enough to let the fibers move around freely; you need not keep track of how much water you used and can add more at any time.
Different dyes work better at different temperatures. Most plant dyes benefit from being heated, but some (i.e. madder) change colors if allowed to boil. Some dyes take best at lower temperatures (safflower and woad/indigo).
For the most even dye job, you should move the fibers around as much as possible in the dyepot. Unfortunately, when wool is heated and agitated it tends to felt, so you must be very careful about how and how much you move it around. For most wools, heat and cool the dyebath slowly and be gentle when moving the fibers to avoid felting.
Wet fibers look darker:
When trying to achieve a certain color, always remember that the color when wet will always appear darker and you may be disappointed when the fibers dry. Also, some color will rinse out as you rinse the fibers. Always dye to a darker shade in the dyepot than you think you need. Lifting your fiber out of the dyepot to "air" is often good for the dyeing process.
You must always rinse fibers after they have been dyed, and some dyes will still bleed for several washings afterwards. As mentioned above, you may want to add some washing soda to plant fibers or some vinegar to animal fibers to return them to their optimum pH in the last rinse.
Natural Dyes are unpredictable:
Books and friends can tell you the range of colors you will most likely get from a given dye source, but there are so many factors involved in the process that reproducing a color exactly can be very difficult. Some reasons for disappointing results could be: insufficient heat, too much heat, accidental iron or other metal contamination in the water, bad growing conditions for the dyeplant, plant harvested at the wrong time of year, dyestuff allowed to dry out, dyestuff kept in humid conditions, dyestuff too old. The point of that list is to stress that you should NOT feel unskilled if you don't get the color you expect - the most experienced dyers in the world get accidental color sometimes. You can overdye, or you can decide you like the color anyway. Colors you consider "ugly" may be termed "gorgeous" or "neat" or at least "useful" by someone else, so giving away dyed material is often a perfect solution.
All content copyright the author, Jennifer Munson firstname.lastname@example.org The author makes no guarantees for instructions and recipes on this site; neither does she accept responsibility for their outcomes. Verbatim copies may be made for educational purposes only provided they contain original copyright marking.
This page created May 4, 2001
Last updated August 02, 2005