Mordanting is an essential step to prepare your fabric to hold on to the pigment you expose it to. There are many ways to mordant fabric because there are a number of different chemical process that work. Plants with high tannin content can act as a natural mordant, but will usually impart a color to the fabric as well. The process I include below is a two step process. I use a recipe I learned from Botanicalcolors.com and I feel that this process gives me very vibrant dye results with long lasting color. You can also purchase mordants from their website.
Once fabric is mordanted, it is always mordanted. You can mordant something and then dye with it immediately, still wet from your mordant bath, or you can dry the fabric (washing or rinsing after mordanting is not necessary) and save it for later. Just make sure to label your already mordanted items so you don't forget. Another important aspect to this process and all dye processes, is to have separate pots and pans and bowls and spoons that are only for dye processes, labelled as such, and never used for food again.
Gather:
- Gloves
- Mask
- Eye protection / glasses
- 2 buckets (I use home depot orange buckets)
- 2 lids
- Aluminum Acetate (powder form)
- Calcium Carbonate (chalk, powder form)
- Teapot or stove top for heating water
- Spoon / stir sticks
- 1 small pitcher (second hand plastic pitcher works great)
- Weighed out and wetted fabric
- Bathtub (or you can do this in your kitchen, or outside, but in the bathtub makes for easy cleanup)
- A timer
Step 1: weigh your items and note what you have in grams. For example, you have 3 t shirts, and your total weight is 400g. I usually mordant in batches that weight about 400 -500g. You want to be able to easily stir your fibers in the baths. Calculate how much of each ingredient listed below that you will need.
Aluminum acetate aka. AA : the recommended amount of aluminum acetate is 5 to 10% of the weight of fiber, or 2-4 rounded teaspoons for 100 grams of fiber. More mordant will increase the depth of shade. I aim for 7%.
Calcium carbonate, aka. CC : the recommended amount of calcium carbonate is 5% of the weight of fiber, or 1 rounded teaspoon for 100 grams of fiber.
Step 2: Dedicate your first bucket to AA, add your fibers/cotton items to the bucket and fill halfway with hot water. I use the hot bathtub water directly from the faucet into my bucket.
Step 3: wearing gloves, a mask, and eye protection, weigh out your Aluminum Acetate or “AA” and add it to your pitcher. Heat up water, it doesn’t need to be boiling but should be hot, add to pitcher & stir to dissolve. Next add this mixture to your AA bucket. Top off with more hot water, stir well. Cover and wait 45 minutes. Stir once or twice during the 45 minute soak.
Step 4: After 40 minutes, you can start preparing your second bath. Fill your second bucket halfway with hot water from the bathtub faucet. In your pitcher, using your PPE, add your needed weighed amount of Chalk aka. CC, then top with a couple cups of warm water. Stir well to dissolve. Then add this to your CC bucket.
Step 5: After your items have been soaking in the AA bath for 45 minutes, using gloves, pull the items out and put directly into your CC bucket. Top off with more hot bathwater, 2cover and stir occasionally, letting items soak for 30 minutes.
Step 6: After 30 minutes in the chalk bath, your items are modanted. You can now take them out and dye them, or you can squeeze the excess water out as much as you can, then add items to a clothes dryer and dry them, or hang on a rack where it’s ok for chalk-water to drip.
This process will not hurt your dryer but you can give the inside of the dryer a quick wipe down after you use it for mordanted items.
Reusing mordant
These baths may be reused at least twice. If you observe cloudiness or flakes floating in the AA bath, it is time to change it. Recharge the bath with 50% of the amount of required mordant, or 1 teaspoon per 100grams of fiber for a 5% solution, or 2 teaspoons for a 10% solution. If you have 800g of items to mordant, perform the mordanting with two rounds of soaking, adding the weaker AA and CC to teh baths for the second batch.