Our word mordant is derived from the Latin word mordere, �to bite�. When you mordant, the molecules from the mineral attach to the fiber molecule. When you dye, the pigment molecules attach themselves to the mordant molecule. There are a number of mordants you may use, some more safe than others.
In some areas of Africa and Asia, mud is used as a mordant. This is where there are large quantities of certain minerals (usually iron and/or magnesium) naturally occurring. You would have to know the chemical make up of the earth in your own region to know if it will work there. I have just recently heard of also using mud as a dye with a soy activator-never tried it though-this summer!
Alum (potassium aluminium sulphate) is by far the most common of mordants and one of the safest. Slightly brightens. This is the one I am most familiar with. Too much can make your fiber sticky and yucky. Unless you are trying to get certain colours or effects, you can easily work with Alum exclusively.
Iron (ferrous sulphate-aka green vitriol, copperas-I have no idea why) is another common mordent and is also used as a dye in the form of rust. Use of iron �saddens� (grays) the colour of your dye. It is often used as a post-mordent to alter the colour of something that has already been dyed. Add to the dye bath at the end of the dyeing process and simmer another 20 minutes or so.
Tin (stannous chloride) brightens the colours of your dyes, especially reds, oranges and yellows on protein fibers. This is known as �blooming�. Too much makes fabric brittle-this one can be particularly hard on fibers if one is not careful. To minimize this risk, you can add a pinch of tin at the end of the dying time with fiber that was premordanted with alum. Tin is not usually used when mordanting cellulose fibers.
** Toxic substance-use with caution. Especially avoid breathing in the vapours of this mordant as it is chlorine-think of bleach but much stronger. Gaa...
Copper (copper sulphate-aka bluestone, blue vitriol) this mordant is used to bring out the greens in dyes. It will also deepen the dye colors, similar to using tin, but is less harsh. Confusingly, some claim it works like iron, greying the colours out-the exact opposite effect from tin! I have some but haven�t been able to use it yet, so I don�t know what it does. Just another example of the need to experiment yourself, I guess.
**Toxic substance-use with caution. Copper can cause illness and allergies with exposure. Do not breathe vapours.
Chrome (potassium dichromate)-light sensitive particularly in solution�you will need to keep a lid on your pot. Used for warm colors. It enhances yellows, reds, and mutes greens. Fiber wise, chrome is most commonly used with wool and mohair. It will give yarn a soft silky feel. Wonderful for dyes-not so wonderful for the dyer. Why are all the best art supplies deadly poisonous?
**Toxic substance-use with caution. There is some controversy surrounding the use of Chrome. Some advocate avoiding it all together. If you choose to use it, be very careful with it. Chrome powder should not be inhaled and gloves should be worn while working with it. Some advise not using it for dyeing clothes or fibers that may be made into wearables for children.
Your local law may require that left over chrome mordant water be disposed of at a chemical waste disposal site and treated as hazardous waste. However you can use it with very little waste by saving the mordent bath in a dark air-tight container to be re-used. When you go to use it again, add 75% of the original amount of chrome back into the dye bath. Continue to add this same 75% each time you use the chrome to mordant your fabric. That way you will not have to dispose of it at all. Remember that since the amount of mordent is proportional to the weight of the fiber, the amount of fiber you use will always have to weigh the same as the original amount.
(e.g. 8 oz fiber-add 2 tsp chrome to the original bath; with subsequent baths you must continue to use 8 oz fiber and add 1 � tsp chrome)
Auxiliaries
Tannic acid-which is found in tea and oak bark. Darkens blacks, sometimes used to mordent on cotton
Chalk is to be used with indigo powder for a colour known as �Saxon blue� or
Sodium bicarbonate-baking soda or better yet�
Soda ash (sodium carbonate) - all for alkalinity (if your water is acidic)
Ammonia-household type with no additives good as an after rinse-conditions yarn
Glaubers Salt (sodium sulphate) levelling agent-that is, it helps the dye take more evenly
Cream of tartar-use with tin and alum to protect the fiber
Vinegar-can be used as a mordent (creating natural acid dyes) or for acidity, also as an after rinse
Oxalic acid-for acidity (if your water is alkaline)
Mordanting Method-there are a few different ways to mordant your yarn or fabric, with pre-mordanting being the most common.
Method 1. After weighing fabric, add proper amount of mordant dissolved in � cup hot water to lukewarm water. When thoroughly mixed, add wetted fiber and stir gently. Bring slowly to the boiling point. Simmer 1 hour. Remove from mordant and let drain. Add to dye bath or allow to dry naturally. With this option, you can mordant all your fiber one day and dye the next if you want, which is good if you are using materials that need to soak for awhile, such as barks, roots or shells.
Method 2. Boil dye plant. Strain dye bath, let cool to lukewarm and add wetted fiber. Simmer 20 min longer. Take wool out and add proper amount of dissolved mordant to dye bath. Then re-enter wool and simmer 15-20 min more. Do not pour the mordant onto your fiber.
Method 3. Add dissolved mordant to dye bath first, then add fiber and simmer required time in recipe. This is what I usually do.
Method 4. Add dissolved mordant to the dye bath at the same time as the plant material.
If you are going to pre mordant (option 1) keep in mind that Alum or Copper mordanted fiber can be placed in a plastic bag or hung to dry, and will last a fair while.
Tin mordanted fiber should be dyed quickly after
mordanting-within a few days.
Iron mordanted fiber should be dyed immediately or stored in an air tight glass container.
Chrome is, as always, light sensitive-store in a dark bag or container.
Also keep in mind that sometimes, with the later three options your mordant and dye material may combine without binding to your fabric, making the dye unusable. This is why pre-mordanting is so common.
How much do you use of a mordant? Remember that the amount of mordant should be proportional to the weight of your fiber, so you will have to weigh the fiber first. Never use too much of a mordant, as it can damage the fiber. Dissolve the mordant salt in � c of hot water before adding it to the bath.
Alum-up to 25% the weight of the fiber, usually plus 6% cream of tartar
Chrome-2-4% of the weight of fiber
Tin-2-4% of the weight of fiber. 0.5 %when used as a post-mordant
Iron-5% of the weight of fiber. Also 6% tannic acid
Copper-I have no proportional data for this one. If I wasn�t so useless at math, I could probably figure it out from the recipes I have.
Or, for those of you who want measurements, for 8 0z (220 g) of fiber (this is from another source)
Alum-up to 2 oz plus � -1 oz cream of tartar
Chrome- � oz-2 tsp plus � oz cream of tartar
Tin-1 tsp
Iron-1 tsp
Copper-1 tsp
Special recipe for mordanting cellulose fibers (cotton, hemp and linen-also rayon) using Alum
The cellulose fibers require the addition of tannic acid (tara powder) or Soda Ash to take up dye well
Weigh your fiber and prepare the mordant bath-heat about 8 c water in a large pot
Dissolve alum-25% weight of fiber in � c hot water. Add to the pot
Measure out Tannic acid-10% weight of fiber. Place this in a nylon stocking and knot. Add to the pot
Add wetted fiber to mordant bath. Simmer for about an hour
Remove fiber and squeeze excess out. Allow to dry naturally.
Some dyers suggest leaving the fiber in the unheated mordant bath for at least 8 hours, or to store damp for a few days to ensure maximum take up.
