[Student Projects, Pigments & Binders]

Natural Dyes and Mordants



Introduction

Procedure

Observations and Data

Conclusion


cotton, linen and wool boards (from left to right)

 

Introduction

The dyeing process involves three factors: fabric, dye bath, mordant. Variations and combinations of these elements can result in very different products. Fabric can be made from numerous materials, both natural and synthetic, as can dyes. For this project only fabrics and dyes made from extractions of natural materials were used (cotton, linen, wool). Some natural dyes have a chemical make-up that will not allow them to bind with various fabrics. Mordants are metallic salts that act on the dye molecules by breaking apart existing links and forming new ones that will bind with the fabric. This project examines the effect of varying one of the three factors in the dye-fabric-mordant combination.

Purpose

The purpose of this project is to study the roles of fabric, mordant and dye in the creation of a final dyed product. All three elements contribute to the resulting shade of the dye stuff and are measurable according to color saturation and colorfastness.

Factors (and Controls)

- Type of fabric (linen, gabardine wool, cotton knit)
- Dye material (coffee, tea, turmeric, indigo)
- Mordant (chrome, alum, chrome-alum, tin, vinegar, tin-vinegar, no mordant)

Measurables

- Color intensity (with colorimeter in L*a*b* color space)
- Colorfastness (through use of basic solution on control group of fabric samples)

Supplies

- 3 hot plates
- thermometer
- 2 stirring rods
- measuring boats
- 5 800-ml beakers
- several watch glasses
- 3 towels
- cheesecloth bag
- linen, cotton, wool samples (1 1/2 in. squares)
- alum
- washing soda
- potassium dichromate
- 4% stannous chloride
- vinegar (5% ascetic acid)
- ground coffee
- black tea
- indigo powder
- sodium hydrosulfite
- turmeric powder
- weighing scale
- colorimeter
- cardboard for mounting of samples
 

Expectations

After reading several explanations of the role mordants play in the dyeing process, we expected that there would be an appreciable difference in our final fabric samples. Mordants and combinations of mordants were said to produce a variety of shades when used with specific fabrics and dyes. We hoped that this would be the case and that the colorimeter test would reflect this. We also expected there to be little change after our colorfastness soap test, since the mordants were supposed to prevent this occurrence.


Procedure

There are three completely different processes connected with dyeing: preparation of the mordants and dyes, mordanting of the materials and the actual dyeing process. In our experiment we used the appropriate amount of materials sufficient for dissolving in 700 ml of water. All the recipes were taken from Natural Dyes and Home Dyeing by Rita Adrosko and Ancient Dyes for Modern Weavers by Palmy Weigle, where the dyes and the mordants are given for one pound of material.

 

Making the Mordants

Mordants used before dyeing:

Alum

-5.24 g alum
-1.310 g washing soda, Na2CO3
-700 ml water

First we dissolved the alum and the washing soda in a beaker with 700 ml of water. We then immersed our fabric samples in clear water, making sure to squeeze out the additional moisture. Next we put the material in the alum solution and stirred it carefully while gradually heating the beaker. The solution boiled for 1 hour, after which we left the material in the mordant bath overnight. On the next day, we removed the material, squeezed out the excess moisture, rolled it in a dry towel, and left it in a cool place until ready to dye. Before using the mordanted material, we rinsed it with cold water.

Chrome

-0.65 g potassium dichromate
-700 ml water

We dissolved the potassium dichromate in 700 ml water and repeated the same steps as in the above procedure for mordanting with alum.

Chrome-Alum

-0.32 g potassium dichromate
-2.62 g alum
-0.35 g washing soda
-700 ml water

For this combination we halved the amounts of chrome and alum from the previous recipes and dissolved them in the same amount of water-700 ml.

Mordants used after Dyeing:

Tin

-1/20 teaspoon of 4% stannous chloride
-50 ml of water

After the material was dyed, we removed it from the dyebath and added the tin (stannous chloride), dissolved into 1/4 cup of water to the dyebath, after which we carefully stirred the solution. Then we put the material back in the dyebath and simmered it for 15 more minutes. After removal from the dyebath, we rinsed the material thoroughly with warm water.

Vinegar

-50 ml of vinegar (5% ascetic acid)
-200 ml of water

Once the material was pulled out of the dyebath, we rinsed it and placed it into a solution of water vinegar. We left fabric in this mixture overnight. The next day we rinsed it again with water.

Tin-Vinegar

-1/20 teaspoon of 4% stannous chloride
-25 ml of vinegar(5% acetic acid)
-50 ml of water

The procedure is the same as in the mordanting process with tin, but after simmering for 15 minutes in the tin mordant, we added the vinegar and simmered the fabric in the solution for another 15 minutes. We then rinsed the samples and pinned them on the boards to dry.

Making the Natural Dyes and Dyeing of the Material.

Coffee

-146.79 g ground coffee
-700 ml water

First we boiled the coffee in water for 20 minutes and waited until it cooled. After that we strained out the grounds. Then we added more cold water to make the 700 ml dyebath. Before immersing the material in the dyebath we rinsed it thoroughly and removed the excess moisture. Finally we heated the solution with the material in it and boiled for 30 minutes. We then rinsed the material and left it to dry.

Tea

-41.95 g black tea
-700 ml water

As with the coffee dye, we first boiled the tea in water for 15 minutes, and subsequently strained out the grounds (instead of loose leaves we used black tea bags). We added cold water to make the 700 ml dyebath and rinsed the fabric in preparation for the dyebath. Then we boiled the samples in the tea dye for 30 minutes. We rinsed the samples with running water and pinned them on the boards to dry.

Indigo

-10.5 g indigo powder
-20.95 g washing soda
-700 ml water
-41.94 g sodium hydrosulfite

The procedure for the preparation of this dye was a little more complicated than the others. We started with dissolving the indigo powder into a small amount of warm water in order to form a paste. In another beaker we dissolved the washing soda in water. After that we gradually added half of the washing soda to the indigo powder paste and stirred it thoroughly. After we got an even mixture,we added half of the sodium hydrosulfite and stirred again. Finally we added enough warm water to have 700 ml of solution and then heated it to 130ºF (around 54ºC). The instructions for the preparation of that dye said that we should not exceed this temperature, because the solution would otherwise not work. After the color of the solution began to turning yellowish-green, we waited for 20 minutes and then spread the rest of the sodium hydrosulfite over the substance, to render harmless any dissolved oxygen. During the preparation of the dye and the dyeing procedure, we had to stir it very carefully in order to keep oxygen from being dissolved into the solution. The dyeing process was very simple-we placed the material in the dyebath for 5 minutes and then remove it carefully. Right after the material was removed from the dyebath, it was yellow-greenish in color, but once exposed to the air it turned blue. We allowed the samples to dry completely before rinsing with running water.

Turmeric

-10.49 g turmeric powder
-700 ml water

First we put the turmeric powder into a cheesecloth bag and soaked it in 700 ml of water overnight. The next day we boiled the solution and allowed it to simmer for 1 hour, after which we waited for the substance to cool. Then we removed the cheesecloth bag and squeezed it to release as much dye as possible. We added more water (the solution was a little bit more than 700 ml). After that, we placed the material in the dye and simmered it for another 45 minutes. Finally we rinsed it with warm water.


Observations and Data

The Measurements

We made two main measurements on our mordanted and dyed samples. The first one was to measure the color of each sample with the colorimeter. The results from this experiment are given in the tables below. The numbers are given in order of L*a*b*, the three axes which are used by the colorimeter to quantify and record color. a represents the horizontal red-green color axis. b stands for the vertical yellow-blue axis. L is an extension through the interception of a and b. Lrepresents the value or the lightness that can be measured independently of color hue.

The dyes produced the following colors in the fabrics (more detailed description below):
coffee--light brown
tea--light brown
turmeric--pale gold
indigo--medium blue

Linen

 L*a*b*  Chrome  Alum  Chrome-Alum  Tin  Vinegar  Tin-Vinegar  Unmordanted
 Coffee  74.9
 4.2
 18.0
 75.1
 4.2
 18.0
 77.4
 3.7
 17.0
 69.6
 4.9
 18.5
 72.9
 3.4
 14.5
 71.1
 4.6
 18.0
 76.4
 3.6
 16.9
 Tea  73.6
 3.9
 15.2
 72.7
 4.9
 16.3
 67.2
 5.7
 16.9
 71.1
 4.6
 17.7
 71.4
 3.6
 13.2
 70.5
 5.0
 18.4
 72.5
 4.6
 16.5
 Turmeric  73.7
 6.0
 73.6
 81.0
 0.3
 68.8
 79.7
 0.2
 66.3
 84.9
 -6.6
 64.0
 84.9
 -7.2
 58.5
 82.9
 -3.9
 65.8
 82.5
 -3.9
 64.5
 Indigo  50.1
 -5.2
 -13.6
 61.5
 -6.2
 -11.9
 51.8
 -5.5
 -13.2
 47.3
 -5.5
 -12.1
 44.0
 -3.8
 -16.3
 49.6
 -4.3
 -15.2
 48.1
 -4.5
 -13.8

Cotton

 L*a*b*  Chrome  Alum  Chrome-Alum  Tin  Vinegar  Tin-Vinegar  Unmordanted
 Coffee  75.5
 3.9
 16.7
 72.8
 4.6
 17.5
 75.0
 3.7
 14.5
 73.5
 3.7
 15.6
 74.4
 3.0
 11.7
 74.2
 3.4
 14.7
 74.6
 3.9
 15.1
 Tea  71.6
 4.2
 14.5
 69.4
 5.0
 15.9
 65.5
 5.7
 17.1
 70.3
 4.3
 18.0
 71.8
 2.8
 10.4
 71.3
 4.0
 16.5
 74.6
 3.68
 14.9
 Turmeric  77.5
 4.8
 70.0
 79.2
 1.8
 71.9
 80.6
 -1.9
 65.5
 83.7
 -4.1
 65.3
 85.2
 -6.1
 61.7
 85.2
 -4.9
 66.3
 81.7
 -3.6
 67.1
 Indigo  52.1
 -5.5
 -11.8
 57.6
 -5.4
 -11.1
 52.4
 -5.5
 -11.2
 57.6
 -5.4
 -12.8
 51.8
 -4.9
 -15.5
 47.2
 -5.0
 -13.0
 58.0
 -5.6
 -13.7

Wool
 L*a*b*  Chrome  Alum  Chrome-Alum  Tin  Vinegar  Tin-Vinegar  Unmordanted
 Coffee  39.7
 11.1
 25.1
 47.6
 12.3
 29.0 
 33.4
 9.5
 22.0
 35.6
 14.2
 28.1
 47.9
 7.9
 22.0
 38.5
 13.7
 30.1
 55.8
 11.0
 29.1
 Tea  32.9
 10.8
 22.3
 31.4
 15.3
 19.6
 31.5
 9.0
 23.6
 40.7
 11.6
 26.1
 40.1
 9.5
 21.8 
 40.8
 11.5
 25.9
 40.9
 11.3
 23.4
 Turmeric  46.5
 19.3
 54.0
 59.5
 18.6
 73.2
 39.8
 19.9
 43.6
&nbsp61.4
 16.5
 60.0 
 71.8
 4.4
 63.3
 64.0
 14.0
 60.6
 67.1
 8.5
 67.8
 Indigo  41.2
 -4.6
 -10.4
 52.5
 -3.9
 -8.2
 30.1
 -4.4
 -10.9
 27.5
 -1.3
 -16.7
 33.7
 -2.5
 -17.0
 30.2
 -2.0
 -16.0
 31.3
 -1.7
 -18.0

The other experiment that we made was for colorfastness. We used only samples of the wool material with all the mordants and indigo dye. For the washing process we used soap, which we spread over the samples and let sit for 20 minutes, after which we washed the samples with warm water. The results given below show that there was no significant difference between the washed and unwashed wool, which means that the mordants we used caused the dyes to stay on the material and not wash away. The differences in the results of the unwashed and washed samples are negligible, reflecting no appreciable fading in color.

 L*a*b*  Chrome

 Alum

 Chrome-Alum

 Tin

 Vinegar

 Tin-Vinegar  Unmordanted
 Wool  42.5
 -5.5
 -7.8
 49.5
 -4.6
 -8.8
 35.8
 -6.2
 -9.7
 34.1
 -2.1
 -18.2
 42.9
 -3.9
 -17.9
 32.8
 -1.4
 -18.3
 39.3
 -3.3
 -17.1

 

Final Sample Observations

Cotton--

- The color of the fabric did not change much after the chrome, alum, and chrome-alum mordanting procedure (undyed samples).

- The color mainly remained the same for each dye lot, regardless of mordant type (no change across horizontal rows).

- The indigo dye resulted in splotchy samples because of the sediment at the bottom of the beaker.

at right, photomicroscopic view of cotton fabric (mordant: tin-vinegar, dye: indigo)

Linen--

- The same observations as with the cotton samples (color homogeneity), except that the indigo dye was more evenly distributed on the fabric.

at right, photomicroscopic view of linen fabric (mordant: tin-vinegar, dye: indigo)

 

Wool--

- There is a much greater variation in shades.

- The mordants either lightened or darkened the shade of fabric in comparison to the unmordanted controls.

- Uneven indigo dyeing as in cotton samples.

- The vinegar mordant resulted in paler coffee, tea and turmeric samples.

- NOTE: the wool samples unraveled during the boiling of the mordant and dye baths. Burning the edges of the samples will prevent this.

at right: photomicroscopic view of wool fiber (mordant: tin-vinegar, dye: indigo)


CONCLUSION

From this project, we learned that all three factors (fabric, dye, mordant) have a definite impact on the final color of the samples. Although the colors on our linen and cotton samples varied little, the wool nicely showed the differences caused by various mordant and dye combinations. The fact that the wool and cotton samples were cut from material that had been laundered and used before may account for the similarities in their dye results. But another reason for the discrepancy in dyes results may be related to the source of the fabrics: cotton and linen are made from materials extracted from plants, while wool comes from animal fibers. If we had had more time, we could have executed longer colorfastness tests, but the results of our brief soap test seem to indicate that the mordants performed their duty in binding the dye to the fabric.


Other web pages with information about the dyeing and mordanting of fabrics:

For more information about natural dying processes, check out Carol Todd's Natural Dying home page (interesting Dyeplant of the Month section with recipes and observations: http://slonet.org/~crowland

To read more about the long history of dyeing, visit this site entitled Dye History from 2600 B.C. to the 20th Century: http://www.straw.com/sig/dyehist.html

Good general information on dyeing and mordanting processes at Kathryn of the Hills' Dye Book: http://www.cobweb.net/~ryn/dyebook.html

For more information about the physical and chemical characteristics of natural and synthetic fibers, visit: http://www.fabriclink.com/characteristics.html


References

Adrosko, Rita J. Natural Dyes and Home Dyeing. New York: Dover Publications, Inc.,1971.

Bemiss, Elijah. The Dyer's Companion. New York: Dover Publications, Inc., 1973.

Weigle, Palmy. Ancient Dyes for Modern Weavers. New York: Watson-Guptill Publications, 1974.

 



Doriana Basamakova, Rachel Hildebrandt 1998.