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How to Dye Wool Fabric & Yarn from Start to Finish (5 Ways)

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Whether you’re dyeing a fine merino knit fabric, an old wool sweater, or some yarn for knitting or crochet, dyeing is an excellent way to achieve exactly the color you’re after. I’ve spent a fair amount of time dyeing both merino wool fabric as well as yarn to knit with. I’ll share my best tips below.

You can dye wool with acid dyes (the best way), box dyes (like Rit, Dylon, and iDye), natural dyes, food coloring, and Kool Aid. While wool isn’t inherently difficult to work with, remember to avoid sudden temperature changes and agitation so your wool doesn’t felt or shrink.

Contents list:

Can you dye wool? Is it easy? 

Wool takes dye vibrantly, beautifully, and evenly. If you want color variation though, it will be more difficult to achieve this because wool wants to distribute color evenly. Wool is also a delicate fabric that will felt and shrink if agitated too much or exposed to sudden temperature changes.

You’ve most likely heard of felting. We’ll cover this more in the shrinkage section below, but felting is one of the key considerations when working with wool. It can cause a wool fabric to change in texture, shrink significantly, and it can cause yarns to matt together and become completely unusable. The key to stopping this is to avoid sudden changes in temperature, and avoid agitation while the wool is wet. Agitation includes things like stirring vigorously, wringing, or overhandling the fabric or yarn while it’s wet.

What’s the best dye and dyeing method for wool?

Acid dyes form a chemical bond with wool fibers, creating vibrant and permanent colors. They do require more equipment though, so may not be suitable for one-off projects.

There are several different types of dyes available, and each one is designed to react with a particular type of fiber. While fiber reactive dyes are specifically formulated to interact with cellulose fibers like cotton and linen, acid dyes are designed to work with wool and silk. Acid dyes form a chemical bond with these fibers, so the resulting dye bath is incredibly vibrant and long-lasting. This makes acid dyes the obvious choice for wool dyeing. 

That said, acid dyes do require a fairly significant set up in order to use. You won’t be able to use any of your dyeing utensils for cooking (including your pot!) and this can take up a fair bit of space, so if the project you’re looking to work on is a one-off and you’re not planning to do more dyeing, box dyes such as Rit and iDye may be a good option. These require a smaller amount of setup and less specialist equipment, but they produce less accurate colors and have a tendency to wash out of fabrics more quickly since they’re not specifically formulated for wool.

Natural dyes are another great option for wool – almost any natural dye will have a beautiful result on wool fabric, and there are very few natural pigments that won’t absorb into wool fabrics. The biggest thing to keep in mind here is the temperature shock when working with higher temperatures. Natural dyes often require heat in order to achieve a vibrant color, and any changes in temperature should happen slowly when working with wool.

Can you dye wool using food coloring?

Food coloring shares some of the same pigment compounds as acid dyes, so it’s possible to dye things that would normally dye with acid dye (wool, silk, and nylon) with food coloring as well. This is a great way to explore the world of dyeing without buying too much specialist equipment. Since food coloring is safe to eat, you can use your normal kitchen utensils for your project rather than buying a full separate set for dyeing. 

That said, food coloring often contains a mix of different pigments, and these can absorb differently in fabric as well as acting at different temperatures (this is called the “strike temperature” – the temperature at which a dye chemically bonds with the fabric). Food coloring is great for learning and deciding whether you like dyeing, but its results won’t be as accurate as pure, concentrated acid dye.

Can you dye wool using Kool Aid?

Yes, Kool-Aid contains food coloring which shares some of the same pigment compounds as acid dyes, so you can dye wool which would normally suit acid dyes. The added benefit of Kool-Aid is that it also contains citric acid which is the catalyst for the dyeing reaction. Kool-Aid is like an all-in-one solution to try dyeing with.

A few notes to keep in mind:

  • Kool-Aid contains a lot less actual pigment than concentrated dye, so you’ll need to use quite a few packets if you’re aiming for shades beyond pastels.
  • It also contains quite a lot of sugar, which doesn’t harm the reaction at all but is going to make your fabric extra sticky if you don’t wash it out thoroughly.
  • Be sure to wash thoroughly using a gentle soap, and if your wool is machine washable, finish the dye cycle with a gentle wash in the machine to ensure everything that doesn’t belong in the fabric is thoroughly removed. If you do this, make sure you keep your washing machine temperature to a cooler setting to avoid undoing all your hard work! 

Tips for dyeing wool sweaters and coats at home:

Dye is an excellent way to breathe new life into a garment, but there are a few things to keep in mind if you’re planning to dye an existing sweater or coat, in order to ensure it retains its original shape and size once the dye bath is complete!

For sweaters, the biggest consideration is temperature shock. Any sudden changes in temperature can lead to felting, so it’s important that you keep all of the changes slow and steady. The heating and cooling of the dye bath as well as the rinse cycles can make a huge difference. You don’t need to machine wash your garment after the dye bath, and you’ll want to stay away from the spin cycle on your washing machine as well! You can lay your dyed garment out to dry on a flat surface (outside in the shade on a towel works well).

For coats, avoiding sudden changes in temperature still applies, but coats often have a hidden under-structure which can make dyeing more complex. To be honest, it’s best to stay away from dyeing structured wool coats: the internal structure consists of interfacings, canvasses, and paddings that are often not pre-shrunk before they’re used in the factory. Washing them, even without dye, can lead to some disastrously puckered results. If you insist on dyeing a coat, first take it apart at the lining to remove all structural layers. Replace these after the dye job is complete. And allow plenty of room in the dye bath for your coat to swim freely.

How to dye wool without shrinkage:

The biggest factor in avoiding wool shrinkage is avoiding sudden temperature shifts. There are others, but if you take one lesson from this blog post, I hope that it is that avoiding sudden temperature shifts is the key to dyeing wool. Whenever you add a wool item to a dye bath, the bath should start as close to room temperature as possible, and be both heated up and cooled down slowly. The cooling can happen naturally – turning off the heat and allowing an item to cool naturally – but some stoves are so powerful that you may want to avoid turning the temperature up to full blast immediately.

The second major thing to avoid is agitation. This means rapid, energetic stirring as well as the bubbling of a boiling pot – any dyeing should happen just below the boiling point. 

The avoidance of rapid temperature shifts and agitation is meant to help you avoid a process called “felting”. Felting is basically a process that irrevocably tangles wool fibers, matting them into a dense fabric that’s impossible to untangle. The nature of this matting means that the fibers contract on each other, which is what causes the shrinkage. Avoiding felting, therefore, is the key to avoiding shrinkage.

How to dye wool fabric using acid dyes (recommended method):

Acid dyes are the best and most reliable method for dyeing wool. They’re specifically designed for protein fibers like wool. They take a bit of setup – a few ingredients and some special tools – but if you’re looking for an accurate color match, predictable results, and a dye that will stand the test of time, acid dyes are perfect for any job where wool is involved.

You will need: 

  • Acid dye
  • Dye activator: Citric Acid (available from your local supermarket)
  • A dye pot made from a non-reactive metal like aluminum
  • Rubber gloves
  • A set of teaspoons
  • Dust mask
  • A small plastic cup and stirring stick (I like a plastic knife) to mix the dye solution
  • Tongs, a stirring spoon, or something similar to stir your dye bath
  • Optional: Kitchen scale (gram increments) and mini scale (hundredths of gram increments) and a thermometer

Step 1: Pre-wash & dry wool item

Pre-wash and dry your wool item using detergent. If it’s a pre-made item, pay special attention to stains as these could affect color uptake.

Step 2: Record the weight of the dry item

Weigh the item you’re dyeing and write down its total dry weight.

Step 3: Pre-soak your item

Fill your sink (or a bowl) with warm water and pre-soak your item while you calculate the amount of dye you need.

Step 4: Calculate how much dye you need

Your dye will come with a suggested recipe based on your items total weight, like “2% of Weight of Goods” – this means in order to get the swatch color, you need to calculate 2% of the total dry weight of your item. 

This calculation is the (Suggested percentage x Total dry weight) / 100
For example, if our item’s dry weight is 150g, and we need 2% dye, the formula is (2×150)/100 for 3g of dye.

If you want to avoid the maths, Dharma Trading has a calculator that tells you how much dye to use based on the dye color and weight of the item.

Note: If you don’t have scales, you can estimate with tablespoons but the colors may not be exact.

Step 5: Mix your dye

Put the dust mask on before you open the jar of dye – most powder dyes are lung irritants, so please be safe. Measure your dye into the plastic cup, and add hot (but not boiling) water gradually, mixing as the dye forms a paste and then a liquid. You can strain this liquid through muslin if there are any granules of dye left undissolved. Once the dye is dissolved and the lid is back on your jar, it’s safe to remove the dust mask.

Step 6: Add the wool item & water to the dye pot. Heat them.

Add your wool item to the dye pot. Then add enough water so that the item will be able to swim freely. It’s important that you start with cold or room temperature water when working with wool items! Heat the water to 185 degrees Fahrenheit (85 degrees celsius). If you don’t have a thermometer, you’re aiming for the stage just before boiling, where small bubbles are forming on the base of the pot but not quite bubbling at the surface. Make sure you don’t let your dye pot boil!

Step 7: Add the dye activator (vinegar or citric acid) & dye mix

Add 1/4 cup of vinegar (or 1 tablespoon of citric acid) per 450g of wool fabric. Before you do this, shuffle your fabric to the side a bit with your tongs or spoon so you’re not pouring directly on the fabric. Then mix thoroughly.

Add the cup of dye in the same way – pushing the fabric to the side to avoid pouring it directly (this helps avoid dark splotches). Mix thoroughly. You can swish a bit of extra hot water in your dye cup and add it to your dye bath to make sure you get it all.

Step 8: Stir frequently until the dye is absorbed. Turn off the heat.

Maintain the temperature and stir frequently until the dye is absorbed – the water in the dye bath will be clear if you’ve done your math right! This is called the “exhaust”.  Once the dye has exhausted (or even if it hasn’t and it’s the color you want), turn off the heat and allow the fabric to cool to room temperature. This will take a while, but you should be able to put your hand on the side of the pot with an open hand before you drain the dye pot.

Step 9: Remove your item from the pot and rinse it

Remove the fabric from the dye bath. Rinse it under warm and then cool water. Wash it with a bit of hand soap and make sure the water runs clear.

If your wool is machine washable, you may wish to follow the in-sink rinse with a run through the washing machine on a cool temperature setting and without the spin cycle. Then it’s time to enjoy your newly dyed fabric!

How to dye wool using box dyes like Rit, Dylon & iDye:

If we think of fiber-reactive and acid dyes as “specialists”, box dyes are generalists. They do an average job on a variety of fibers, whereas acid dyes and fiber reactive dyes do an excellent job on the specific fibers they’re designed for. If you’re looking for a one-off dye project with only a few required materials, box dyes can be a good option. But keep in mind that the resulting colors can be less accurate, they tend to fade faster, and there’s a risk of bleeding during washing.

These dyes are usually made from various mixtures of acid, fiber-reactive, and sometimes other dyes to create a multipurpose dye with a bit of everything. This means the concentration of the dye you need will be lower – but they can be useful if you’re dyeing a pre-made garment made from many types of fibers.

The three brands of box dye explored here are Rit, Dylon, and iDye. Personally, I normally recommend pure acid dyes for wool – but if you’re choosing between box dyes, I have had the least reliable results with Rit, and the best results with iDye. This option seems to be more permanent (in my experience) and the colors I’ve gotten have been the most accurate of the three.

You will need:

  • Box dye of choice.
  • Vinegar (for Rit or iDye) or Salt (for Dylon).
  • A dye vessel like a plastic bucket, or a stainless steel pot.
  • Rubber gloves.
  • Tongs, a stirring spoon, or something similar to stir your dye bath.
  • A set of measuring spoons. Since you’re only using these for salt or vinegar, you don’t need a special “dye only” set – your regular kitchen ones are fine.
  • Optional: a kitchen scale to weigh your fabric.
  • I also strongly recommend a thermometer – a candy thermometer or meat thermometer will work well.

Step 1: Pre-wash & dry your wool item

Pre-wash your fabric, and stain treat it if required (stains affect color intake). Allow the item to dry.

Step 2: Calculate how much dye you need

Follow the package instructions to estimate the amount of dye needed. Generally, this is one or two packets per pound of fabric, but this differs by brand and color chosen.

Step 3: Add your item & water to the dye pot

Add the fabric to your dye vessel, and fill it with enough hot water for the fabric to swim freely. These dyes can be used in a bucket with hot water, or in a pot on the stove. Using the stovetop method is the best way to get brighter and darker colors. You want to be very careful to stay below the boiling point of the water, as the agitation of the water makes the wool more likely to felt. This is 212 degrees Fahrenheit or 100 degrees Celsius.

Step 4: Add the dye activator (salt or vinegar) and dye packet

Add 200ml vinegar (for RIT), 78ml vinegar (for iDye) or 10 tablespoons of salt (for Dylon) – per packet of dye. Mix thoroughly.

Add dye, being careful not to pour it directly on the fabric (this could cause dark spots).

Step 5: Stir frequently until the dye is absorbed

Stir constantly for the first ten minutes, then frequently for at least an hour. If you’re going for a pastel shade, this may take less time. These dyes can be left for several hours or overnight. The dye won’t exhaust fully, so expect the water to still be colorful even though the fabric is done.

Step 6: Remove the wool item from the pot & rinse it

Remove the fabric from the dye bath and rinse it in hot water first, then slowly switch to cool water until the wool item runs clear. Wash it with a bit of hand soap. Rit recommends washing your item in a color fixative for maximum color-fastness, which you can find here. Be mindful of sudden temperature shifts with wool – make all changes slowly, as sudden shifts in temperature may ‘shock’ the wool into felting.

How to dye wool naturally:

Wool is an excellent candidate for natural dyeing, and absorbs many natural dyes with ease. Here’s my step-by-step guide on how to naturally dye things.

When naturally dyeing wool, remember to make sure that any environmental change (acidity, temperature, etc) is allowed to happen slowly, to ensure the wool doesn’t felt. This means that anytime you bring a pot of water to boil or cool down, make sure this happens slowly enough that the wool can acclimatize to the change. Avoid agitating the wool in the dye bath to avoid felting and shrinkage. Slow stirring to achieve an even dye result is fine, but try to keep movements to a minimum when possible.

Will the dye be permanent?

If you use acid dyes for your wool project, the chemical reaction of the dye will create a strong bond with the fibers, so the color will be almost permanent for the entire life of the garment. All fabrics will fade over time though, especially if left in direct sunlight or washed in hot water, but you can prolong the life of a dyed garment by washing it in cold water, line drying the wool item in the shade, and keeping it out of direct sunlight as much as possible.

Box dyes like Rit and Dylon tend to create colors that fade faster and wash out. This is because they’re not specifically formulated for wool.

What to read next…

This article was written by Kat Waters and edited by Sara Maker. It was originally published on 12 September 2022 and has since been updated.

Kat Waters (author)
Kat has been sewing since her feet could reach the pedals, starting with quilts she made with her mom and eventually graduating to garments. She now makes everything she wears, occasionally teaches classes, and shares her projects on social media. Highlights include her wedding dress, shoemaking, and a love for almost any fabric that comes in hot pink! Read more…