Lab Summary Week 5
Olivia, Bianca, Feraidon
Introduction
This week, our class continued in our studies related to ancient shepherding and related processes by studying the dyeing of wool.
To prepare for this lab, we examined historical and archaeological evidence of dye use in various civilizations, including Minoans, Romans, and Mesoamerican cultures. In addition, we watched the documentary “In Search of Lost Colour” which documents the growing, harvesting, extraction and use of natural dyes around the world. It also traced the evolution of color production from traditional plant and insect-based dyes to modern synthetic alternatives. The final sources explored this week were a page from the US Forest Service on Native Plant Dyes and a published experimental archaeology article on dye by Carleton alums.
The processes of this lab took place across several days (not to mention the usage of wool and yarn prepared in the Week 2 Lab). It started with preparing the wool for dyeing a day in advance. Then, we traveled to a local farm for the actual dyeing. Lastly, the next day, the wool was examined, washed, and left to dry.
Methods
Methods: Mordanting
The first part of this week’s lab process began on Wednesday (April 29th) during class time beginning around 11am. During this period, we mordanted the products that we planned to dye. Mordanting is a preparatory treatment that helps dye chemically bond to fibers, improving both the vibrancy and durability of the resulting color. For this process, groups used aluminum sulfate or alum (Al2(SO4)3) as the mordant, which was purchased in bulk at an outdoor supply store.
A variety of wool types were prepared, including hand-spun yarn from previous labs, commercially spun wool, carded wool roving, and uncarded locks. Each group weighed their wool prior to treatment in order to calculate the appropriate amount of mordant to use. Across the class, aluminum sulfate was added at approximately 12–20% of the total wool weight.
The wool was submerged in water and gradually heated throughout the class period. To avoid the need for starting fires during a limited class period, boiling water from a kettle was periodically added to raise the temperature. During the adding of water, students stirred the mixture and monitored the temperature. Groups aimed to get the solution to at least 160°F. The wool was then left soaking in the mordant bath until approximately 4:00 pm to allow the treatment to fully penetrate the fibers. Once cooled to room temperature, the wool was rinsed in cool water and was then ready for dyeing.
Observations made later after the dyeing stage demonstrated that mordanting had a substantial effect on dye absorption. Mordanted wool consistently produced deeper, more vibrant colors than unmordanted samples, confirming the importance of the mordanting process in natural dyeing.
Methods: Dyeing
In this lab, our six groups combined to study the effects of three different types of natural dye: weld, madder, and walnuts. To perform this part of the lab, we traveled to Get Bentz Farm, where local farming experts Maddie and Theresa had prepared the three natural dyes for our use.
Dye expert Maddie had soaked each type of dye in hot water beginning at 12:32 pm the day before, about 25 hours before our experiment began, and let the ingredients warm in the sun shortly before we arrived. At the end of the lab, each group hung the results of their experiment on a wire rack to dry outside overnight.
For this section of the lab, we utilized the iron pots holding soaked wool, a thermometer to check the temperature of the dye mixture periodically, a durable fire, and an iron stand positioned over the fire on which the pots hung. Our process consisted of several steps.
- Add prepared dye ingredients to pot with soaked wool
- Hang pot over a strong fire. The pot’s lid can be used as a tool to regulate the temperature
- Let wool simmer at the dye’s ideal temperature for 60-70 minutes
- Continuously check wool’s temperature, making sure it does not exceed or fall below the recommended temperature range
- Remove the pot from the fire at the end of the experiment
- Hang dyed wool on wire rack to dry overnight
Weld Dye
Groups 1 and 2 studied weld dye, which is expected to produce a yellow color. Weld dye is created from weld, a native plant, with the plant’s leaves and florets included. The groups added their weld dye to the pot containing both mordanted with unmordanted wool, which they wrapped on a wooden spoon. Unfortunately, the unmordanted wool was not fully submerged throughout the process, while the mordanted dye was, potentially impacting the results. The groups hung the pot on the fire at 2:17 pm and removed it at 3:25 pm, for a total of 68 minutes, adding a handful of fresh weld at 2:43 pm to observe its effects compared to the initial processed weld.
Weld: Temperature
The optimal temperature at which weld dye should be simmered is between 160 and 180 degrees F. Maddie warned that too much temperature fluctuation would result in the weld sealing up and being resistant to dyeing, so group members had to watch the temperature carefully throughout the process. The groups recorded how the temperature of the pot changed over time using the thermometer, which they mounted to the side of the cast iron pot, and switched the pot on and off the fire periodically in an attempt to keep it in the optimal range.
Madder Dye
Groups 3 and 4 studied the madder root, which is expected to produce a red color. Madder grows locally in Minnesota, and the color derives from the plant’s roots, which are insulated by a dark red flesh that has the texture and color of a beet. The groups added their pot to the fire around the same time as the weld group, leaving the madder to simmer for about 75 minutes. At the end of the lab, it took the groups about 5 minutes to remove all of the dyed wool, which they hung to dry overnight.
Madder: Temperature
Madder root is the most temperamental type of natural dye we studied, needing to be kept between 140 and 175 degrees F to prevent browning. Maintaining this temperature window required recording the dye’s temperature every minute and removing the pot or lid periodically.
Walnut Dye
Groups 5 and 6 studied walnut dye, which is supposed to produce a dark brownish/black. After soaking, the walnuts had broken into fragments, producing the optimal color. The groups placed the walnuts in with their wool and simmered the mixture from 2:13 to 3:24 for a total time of 71 minutes. To assess how well the dye penetrated different types of yarn and wool, the groups wrapped some spun wool around wooden spoons while keeping some in ball form.
Walnut: Temperature
Walnut required the least attention as there was no prescribed temperature range, as long as the mixture stayed at a rolling boil. The groups removed the pot whenever it started to boil over and put it back on when it had cooled a significant amount.
Results
Weld
The weld dye produced the weakest result of the three dyes. Gray wool showed almost no color change, and white mordanted wool acquired only a faint yellowish-green color. The unmordanted samples showed no discernible change. One noteworthy finding was that the most visible yellowing appeared on areas of wool that were in direct contact with fresh weld stalks added mid-process (at 2:43 pm), rather than the pre-processed plant material. The dyeing process itself was pretty relaxed and only required occasional temperature checks, so it felt like something that could easily be done alongside other tasks.
The poor results were likely due to the darker gray wool overpowering the light dye, along with possible differences in how strong the weld solution was. Weld is usually known for producing a reliable yellow color, so lighter wool or better temperature control may have produced stronger results.
Madder
The madder root was the most difficult dye to manage because the temperature had to stay within a 35°F range.. Groups 3 and 4 recorded temperatures every minute and moved the pot on and off the fire, while also using a lid to control the heat. Even though this was challenging, they were able to keep the dye bath within range for most of the 75-minute session.
The results were also the strongest visually out of the three dyes. Mordanted white roving and white mill-spun wool turned a vivid reddish orange. The mordanting step appeared to make a major difference since the mordanted and unmordanted mill-spun wool showed a clear contrast in color depth. Gray unmordanted mill-spun wool looked almost unchanged after dyeing. The unspun roving also seemed to partially felt during the process. Wool that was not fully submerged developed uneven, gradient-like coloration, showing that how deeply the wool sat in the bath affected how much dye it absorbed.
Walnuts
The walnut dye was the most easiest of the three to manage because the pot only needed to stay hot and did not require strict range. Groups 5 and 6 let the temperature to fluctuate a lot, taking the pot off the fire when it started to boil over and putting it back once it cooled down. Temperatures ranged from about 90°F to 212°F during the dye session.
The results were also the most consistent. All of the wool types, including professionally spun string, hand-spun yarn, and roving fibers, developed a similar light brown color whether they were wrapped on spoons or left loose. Unlike the other dyes, walnut seemed to bond well without needing a mordant, which made it the easiest and least technical dye tested in the lab.
Comparative Analysis
| Factor | Weld | Madder | Walnut |
| Dye Color | Yellow-green (faint) | Reddish-orange (vivid) | Light Brown (consistent) |
| Temperature Sensitivity | Moderate (160-180°F) | High (140-175°F, strict) | Low (just keep hot) |
| Mordanting Impact | Minimal visible impact | Very Significant | Minimal |
| Best Fiber | White mordanted wool | White mordanted roving | All fiber types evenly |
| Worst Fiber | Gray unmordanted wool | Gray unmordanted wool | N/A (consistent) |
| Complexity | Low | High | Very low |
| Effort / Attention | Low | High (every minute) | Very low |
| Smell | Pungent / earthy | N/A | N/A |
Across the three dye types,a few clear patterns appeared:
- Mordanted wool absorbed dye much more effectively than unmordanted wool, especially with madder and weld.
- Gray wool generally produced weaker results than white wool across all three dyes, probably because the darker starting color masked lighter pigments.
- The roving (unspun carded fiber) absorbed the most dye overall, possibly because its loose structure exposed more surface area to the dye bath.
Discussion
This lab gave us a more hands-on understanding of how pre-industrial dyeing may have worked in practice. One thing that became obvious was how different the labor requirements were between dyes. Madder required constant monitoring to keep the temperature within range, while walnut and weld were much easier to manage and allowed us to work on other tasks at the same time, like petting the sheep and kittens. In a historical setting, that difference would have mattered a lot for time and labor organization.
The mordanting step also made a major difference in the final color results, particularly with madder. The contrast between mordanted and unmordanted wool showed how important preparation was for producing vibrant colors.
Another consistent result was that roving absorbed dye more strongly than the spun yarn samples. This suggests that the fiber processing may have affected when textiles were dyed historically.
Wool that was not fully submerged developed uneven coloration, showing how important stirring and pot size were during the dyeing process.
Walnut produced the most reliable results overall, even without strict temperature control or mordanting. Because of this, it seems likely that walnut would have been a practical everyday dye in areas where walnut tree were common. Madder produced the brightest and most visually striking colors, but it also required much more careful control.
Conclusion
This lab demonstrated the complexity and benefits of natural wool dyeing. Through using weld, madder, and walnut dyes, we observed how different dye materials required varying levels of labor, technical knowledge, and environmental control. Madder produced the most vivid results, but it also demanded the greatest amount of attention and precise temperature management. Walnut dye proved to be the most forgiving and reliable, producing consistent coloration across all wool types even under fluctuating conditions. Weld produced the faintest coloration in our experiment, though the results suggest that other factors likely influenced its effectiveness.
Several patterns emerged across all three dye types. Mordanted wool consistently absorbed dye more effectively than unmordanted wool, confirming the importance of mordanting. White and lightly processed fibers, especially roving, also took dye more successfully than darker or tightly spun wool. Additionally, uneven submersion produced uneven coloration.
Beyond the specific dye results, this lab provided valuable experiential insight into the labor and skill involved in ancient dyeing. Dyeing was not simply dipping wool in a pot, but rather a specialized stage of production that required knowledge of chemistry, fiber preparation, and heat management. The differing labor demands of the dyes also suggest how ancient people may have selected materials based not only on color preference, but also on available time, fuel, and technical expertise. Overall, this experiment deepened our understanding of how natural dyes function, how textile production operated historically, and the benefits of natural dyeing in modern society.
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