The Indigo Apprenticeship Program
A collaborative effort between Blue Light Junction and Rosa Sung Ji Chang (장성지) from the Indigo Shade Map Project
Rosa Sung Ji Chang & Blue Light Junction are launching their first Indigo Apprenticeship and Study Group Program this summer. The goal of the program is to offer hands-on, experiential training in the cultivation, harvest, and pigment-making process of Polygonum tinctorium (jjok, 쪽). In addition to learning practical skills and sharing cultural stories, we’ll explore how this work can support community, sustainability, and personal resilience.
Over the past five years, Rosa has been developing and refining the pigment extraction process using indigo plants grown at Blue Light Junction. Now, she invites participants to join her in this inaugural program, which focuses on hands-on practice, learning, and shared labor.
Learn more about Rosa’s practice and her Indigo Shade Map project.
Follow the Indigo Extraction Process
This program is rooted primarily in Korean and Japanese indigo traditions, reflecting the background of Rosa Chang, who studied extensively in both regions and is leading the Indigo extraction process.
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1st Harvest
July 15, 2025
The inaugural Indigo Apprenticeship Program, in collaboration with Indigo Shade Map, officially launched on July 15, 2025.
For our very first summer harvest, we collected over 100 pounds of fresh indigo from Farm Alliance’s Black Butterfly Teaching Farm, where the seedlings were initially started and transplanted by Blue Light Junction.
Photo by Timothy Prieto @timothyprieto
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Stage One
July 15, 2025
The species of indigo we harvested is Polygonum tinctorium, also known as Persicaria tinctoria. This plant is native to East Asia and plays a central role in many of the practices taught during our sessions. In the United States, it is commonly referred to as Japanese Indigo or Asian Indigo. In Korean culture, it is called Jjok (쪽), and in the Philippines, it is known as Malatayum.
After the harvest, we gathered together and continued our work on the first stage of indigo extraction at the Natural Dye Garden “Annex,” which is located right next to our studio.
Photo by Timothy Prieto @timothyprieto
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Soaking the Leaves
July 15, 2025
After a thorough rinse, the plants were soaked in a large water-filled tub—eagerly awaiting the transformation into vibrant turquoise indigo water.
Photo by Timothy Prieto @timothyprieto
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Community
July 16, 2025
Our friend and fellow farmer, Sarah Sohn, dropped off 56 lbs of indigo she seeded from growing with Blue Light Junction. Some of this indigo was started from our workshop “Indigo & Cotton Growing” with Kenya Miles in March 2025.
This moment reflects how a part of this program focuses on valuing community and shared labor, marking a huge milestone after five years of cultivating together.
Photo by Kenya Miles
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Next Phase
July 19, 2025
After a few days, the water began to change from a greenish color to a distinct turquoise-teal hue. This color shift indicates that the fermentation process has broken down the cell walls of the leaves, releasing the indigo precursors into the water, signaling that the leaves are ready to be removed.
Once the leaves were removed, we allowed the remaining liquid to sit undisturbed for one to two more days. This allowed the pigment to settle and initiated the reduction preparation.
Photo by Amber Likins @amberisknitting -
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Stage Two & Three
July 22, 2025
This alchemical process requires careful attention to timing and observation to determine when the indigo is ready for the next step.
After two days, a shimmering film that forms on the surface of the liquid indicates that the fermentation process has completed. The pigment is now ready for stage three: adding alkaline, which prepares the bath for oxidation. This oxidation transforms the reduced indigo into a visible, insoluble blue pigment.
Photo by Amber Likins @amberisknitting
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Stage Four
July 22, 2025
Immediately after adding lime, we began the aeration process to oxidize the indigo. The vat was stirred vigorously for 15 to 30 minutes until bubbles appeared on the surface. As we took turns aerating, the white bubbles transformed into blue bubbles, and the liquid changed from teal to a deep blue.
Photo by Rosa Chang @rosaful_garden
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Stage Five
July 22, 2025
A subtle carbonated “fizz” or crackling sound often accompanies the final phase of pigment oxidation, indicating that we have reached the peak of transformation. At this point, the liquid is ready for its settling and resting period. After aeration, we covered the container and allowed it to sit undisturbed for three days, enabling the pigment particles to settle at the bottom.
To be continued…
Photo by Amber Likins @amberisknitting
THE STUDIO
Located in Central Baltimore’s Station North/Greenmount neighborhood, Blue Light Junction operates as an alternative color lab, educational facility, and gathering space.
We center our practice in global traditions and knowledge bearers of craft and natural dye. focused on growing, processing, and preserving natural dyes through their histories, traditions, enhancements, and use in everyday objects.
We offer education-based workshops and events, knowledge transfer through apprenticeships and classes, and sustained research and experimentation through the Ibura Art and Research Residency.
