We all know the colors of the American flag. But how did those colors physically come to fly on flagpoles and inspire national anthems? When people in the flag's era wanted to put colors on fabric, the answer came down to dye.
Dyeing has been used for most of human history to add color to textile products, including yarn and fabric. Nowadays, chemists add synthetic dyes to many synthetic materials before the fibers are even created. For the thousands of years prior to the invention of synthetic dye in 1856, artisans had to use natural, plant-based dyes for fabrics. Only about eight colors were available from plant-based dyes: red, blue, yellow, green, black, brown, orange, and purple.
Natural dyes were necessary to create the colorful broad stripes and bright stars that Francis Scott Key saw so gallantly streaming at the Battle of Baltimore in September 1814. The fabrics would have been pre-dyed before Mary Pickersgill, her two nieces, her daughter, and her indentured servant began work to create the Star-Spangled Banner flag.
Pickersgill created the flag from three fabrics. White cotton was used for the stars, which retained the cotton's original color. Undyed wool was used for the white stripes. She used dyed wool for the blue star background and red stripes.
The wool for the starfield background was dyed with indigo. Indigo, possessing a deep, rich blue color, is one of the oldest natural dyes for fabrics and is created from the leaves of the plant Indegofera tinctoria. Note that the term "tinctoria" in the indigo plant's scientific name comes from the Latin root "tinctorius," which refers to dyeing or staining.
Indigo, like many other plants, was introduced to the Americas from across the ocean. In the 1740s, South Carolina planters were searching for new cash crops to support their colony's plantation economy. When she was only a teenager, South Carolinian Eliza Lucas, whose father was the governor of British Antigua, experimented with and successfully introduced a profitable strain of indigo from the West Indies. By the 1770s, indigo was a staple crop in the American South, comprising one third of South Carolina's exports.
The wool for the red stripes was dyed red with the root of the madder plant, Rubia tinctorum. (There's that "tinctorius" root again!)
Madder root dye can produce reds of many different shares, from peaches and corals to deep burgundies. To get the right shade of red, the madder root has to be combined with mordants, metallic salts that help set and intensify natural dyes. Mordants help protect the dyed cloth from perspiration, water, and fading over time. The pH of the dye bath also affects the final color so many different shades can be achieved by altering the pH with the same mordant.
The colors and shapes of flags have been used to denote military units, mark territory, and inspire national pride. Americans identify with "red, white, and blue" as a national and personal concept. Without the use of dyes to help create the distinctive hues of the American flag, we would not have had the Star-Spangled Banner to inspire Francis Scott Key, or the flags that we proudly fly today.
Daniel Holm is an educator at the National Museum of American History. Background information for this post was adapted from the activity "Star-Spangled Banner: The Technique of Natural Dyeing", presented by the Lemelson Center for the Study of Invention and Innovation. We also invite you to have a Star-Spangled Summer, hear from Mary Pickersgill, and peek inside our conservator's project to preserve the flag forever.
Goose bumps.
Chills.
Tears.
These are just some of the things visitors tell us they experience when they see the flag that inspired our national anthem.
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