Natural Dyes for Wool: Hemp

By Hannah Thiessen on March 20, 2021

With the advent of medical marijuana and CBD legalization sweeping the world, I’ve been seeing more opportunities to work with one of the oldest natural dyes: hemp. Hemp has long been used as a fabric and material base, but did you know that it’s also possible to dye soft yellows with the stems, stalks and leaves of the hemp plant?

When I moved into my home last year, I was surprised to find out that my next door neighbor is a CBD farmer, and he gathered a huge bag of leftover stems and stalks from their annual harvest for me to try my hand at dyeing with. While these dried, leftover elements have less color than the leaves would, I thought it would be worth it to give them a shot in the dyepot using many of the same methods I’d use for other wood-based dyes, like Brazilwood, Osage, or Cutch.

How to Naturally Dye Wool with Hemp

Materials

For this dye experiment, you’ll want the following materials on hand. Remember, anything you use for natural dyeing must not be used again for food or food prep at any time, and you’ll want to store it separately to avoid any cross-contamination.

• 1-2 large stainless steel or aluminum soup pots or stock pots
  This should be big enough to hold 1-2, 100 g skeins of yarn, covered in water and fully submerged with room to move around. If you only have one, you will need to mordant the yarn overnight, strain and wash the pot, then prepare the dye in the same pot, re-wetting the yarn and adding it to the dye bath on the 3rd day of the process, instead of being able to do both the dye prep and mordanting on day 1.
• Dedicated tools: measuring cup, spoon for stirring
• A heat source
  This could be your at-home stove with good ventilation, a hot plate, a propane burner or even a crock pot. If you’d like to use an upcycled crock pot, you will not need the stock pot, but it will need to stay fully dedicated to natural dyeing as dyes are not food safe.
• A water source
  Natural dyes do use a lot of water–for prepping your fibers, creating dye baths, and rinsing finished yarns. You can use rainwater if you like, especially if you find your tap water is influencing your colors negatively. You can test your water’s pH with strips and see how ‘neutral’ it is if you like.
• A respirator or face mask
  You’ll need this for the alum in this dye experiment, but not for the onion skins.
• A scale that can measure grams in small quantities
  If you already have a baking scale, you can use it here, just make sure not to let any dyes or materials touch the scale directly. Simply use the tare function to zero-out the weight of any vessels you’re using to measure, then clean off your scale thoroughly after use.
• Aluminium sulfate or Aluminium Potassium Sulfate*
  Mordants are chemicals that bind to both the fiber and color, acting as a bridge to attach color molecules to your wool. This chemical is the safest of a handful of options and is popular with many natural dyers. It will only bind color to protein fibers, not cellulose ones–so color taken by the wool may not be taken up the same way by any blended fibers (like cotton, hemp, linen or nylon).
• Cream of Tartar*
  Cream of Tartar adds a little softness back into your bath and prevents your wool from feeling too crunchy at the end of the dyeing process.
• Hemp stalks & stems
  I used a greater than normal weight ratio of stems and stalks, to compensate for what I believe is a lower concentration of dye in these pieces. My ratio was approximately 1.5:1 dye goods to fiber.
• 2 skeins of Knomad Latte
  For this dye experiment, I’m using Knomad Latte, a 100% Baby Alpaca yarn with the most delightful halo and softness.
• Old clothes
  We’ll be working with iron and bright yellow dye, so it’s better to avoid surprises.
• Gloves
  Rubber gloves or kitchen gloves, which can be re-used multiple times, are my preference here. While most natural dyes are perfectly safe to handle with your hands, you’ll be washing, rinsing, and in and out of water a lot, which can damage your nails and cuticles. Keep those knitting hands pretty and get some gloves.

*These items have been pre-calculated in the amount you need for this project, dyeing 200 g of wool, however, you’ll find what you need to do your own calculations using the mordanting guide below.

Step 1: Prep your fiber. Knomad pre-scours and washes their yarns before shipping them to us, so there should be no need to heavily clean the fibers–simply remove the tags, leaving all the ties, and open the hank into a big loop. Add reinforcement ties if you feel they’re necessary, and soak the fiber in warm water for an hour to get it fully saturated (typically 1 hour).

Step 2: Measure the alum. Wearing a respirator or face mask, measure out 12% of your weight of fiber (WOF) in alum sulfate. Here’s the math for our experiment:

200 x 0.12 = 24 g of aluminum sulfate
Hot tip: weigh out how much alum is in a tablespoon (dedicated tablespoon) and then calculate moving forward about how many tablespoons you’ll need to simplify future measuring.

Step 3: Add hot water to your alum in a small mixing container. I like to use empty, recycle-ready plastic containers. Stir the alum and water mixture until the alum is fully dissolved and the water looks cloudy or clear, but has no visible grains in the bottom of the container. Measure out 1 tbsp of Cream of Tartar and dissolve it into the water while it’s still warm.

Step 4: Transfer your mordanting solution to a larger stock pot, and fill with enough water to cover your skeins of yarn (don’t add them until the pot has all the water in it). Stir and then add your yarn, moving it around to let it fully absorb the mordanting solution. Set on low heat and simmer (do not boil) for 1 hour. Allow to cool overnight with the yarn in the solution.

If you have only one pot, you’ll need to wait until tomorrow to do this step. If you are using more than one pot, you can prepare the dye bath the same day that you mordant as follows.

Step 5: Create your dye bath.
This hemp dye bath needs to steep for 1 hour, then have approximately 12-24 hours to fully develop. You may decide to make your dye bath ahead of everything else and see how rich you can get the color to be before you add yarn. For this experiment, I broke down the twigs and stems into more manageable pieces, then boiled in water for 1 hour before taking it off the heat and allowing it to develop overnight. Even with this extended amount of time, my bath was a very clear yellow–for a stronger tone, I might let the twigs soak in a bucket for a few weeks rather than hours.

Leave your dye bath overnight to fully develop.

Step 6: On the day you are ready to dye, strain your dye bath into a cookpot, removing any sticks, stems or vegetable matter.

Step 7: Prepare the yarn. Drain the water from your yarn soak, and push a little of the extra retained water out with your fingers. Not too much–liquid being held by the fiber will help draw the dye into the yarn, so we don’t want to take it all out and risk too much splotchiness in the final fiber. Add your yarns genty to the dye bath, making sure that yarn has enough room to move around but is mostly submerged in the pot. If you need more water, it’s okay to add some here.

Step 8: Place your pot on the heat source of your choice and increase the temperature gradually to a heat just under simmering. If you have a thermometer, you’re going to first lift the temperature to 90 F (32 C), stir, and then lift the temperature again to 180 F (82 C). I don’t have a thermometer, so I just eyeball it, and that’s okay too. You want the water hot enough for steam to be rising off it, but not so hot that it’s bubbling, boiling, or moving your yarn around for you. Keep the dye bath at this temperature for an hour, stirring occasionally to move the fibers around and keep them from collecting dye only on one side. After an hour, turn the heat off and let it cool.

Step 9: Lift a bit of your yarn from the pot and evaluate the color–with onion skins it can develop quickly and strengthen slightly as it cools. If you like the color as-is, remove the yarn from the pot and move to the next step. If you would like to see the color deepen or strengthen a bit, leave it in the pot overnight, stirring one more time before you go to bed.

Step 10: Remove your yarns from the dye bath and smoosh out some of the extra dye–set the wool aside. Fill a sink, basin or bucket with room temperature water and add your yarn, moving it around with your hands to allow dye release. When the water is dark, drain it and do this step again. Rinse until the water is mostly clear to ensure that no dye particles will transfer to hands or clothing while working with the finished yarns. If you want, you can add a little bit of wool wash to one of these rinse baths to improve the softness and scent of your finished yarn.

Step 11: Hang your hanks of yarn to dry out of the direct sun (I like to use a portable hanging rack in the bathtub). They will drip a little bit, so if you need to dry them indoors, I suggest putting them in a bathtub or in a room with a drain (like a basement). Depending on your humidity and weather, it can take 1-2 days for yarn to fully dry, but maneuvering it so that the same part of the hank is not always hanging down can help move this process along a bit.

I hope some of you might also live somewhere that you’ll be able to try this more unusual dye material, and we can re-capture the interesting color range I’m sure this plant offers us. Right now there’s not a lot of information available online about dyeing with hemp, so please let us know if you’re able to try this experiment and get different colors!