MORE THAN All You Need to Know to Make Your Own Indigo Dye Vat
SKIP AHEAD FOR INSTRUCTIONS, Materials and Notes on Both
T.M.I to follow regarding Indigo's plant origins, the nature of the pigment and a bit of Vat chemistry.
INDIGO IS AN ORGANIC PIGMENT THAT CAN BE GROWN IN PLANTS
Indigo pigment is produced within the leaves of a broad range of plants across an array of genera. They have been historically grown on different parts of the earth that suit their particular needs (sun, moisture, soil, etc). Varieties range from Indigofera Suffruticosa in Central America, Persicaria Tinctoria in Asia, Isatis Tinctoria throughout Northern Europe and Indigofera Tinctoria primarily in South and Southeast Asia. I grow and have extra seed for each of these varieties, please get in touch if you are interested in growing any of them. You can certainly find a variety that you could grow in your local climate.
These plants each contain only a small percentage by weight of actual dyestuff in their leaves. It can take tons of plant material to make a few pounds of dyestuff. One way or another, the pigment is extracted from the leaves and can be purchased in a concentrated, powdered, ball or brick form. This indigo concentrate is often graded on its Indigotin content level, the percentage by weight of actual pigment. Indigotin levels of quality dye concentrate almost always range between 20% and 50%.
The indigo pigment molecule is non-reactive in water. It cannot be dissolved (like salt for example), but it can and must be put into liquid suspension as a first step to making an Indigo vat. The easiest type of Indigo to work with, as well as the most common in the marketplace, is concentrated pigment in finely ground powder form from the plant Indigofera Tinctoria. All processes that I'm describing here presume that is the dye product you're working with. There are a wealth of other indigos out there, both natural and synthetic, most all of which you can treat similarly to this and get good results.
The indigo pigment molecule, as purchased, will not react with cloth or dye it. It can be rubbed in and will cause a temporary stain, but it is not dye. For the indigo to actually transfer and adhere with the cloth, we must create what is called a Vat. The Vat will be referred to with a capital V here, for at the scale of the individual dyer, the entity known as the Vat has an incredible amount of history and personage, requires pampering and sustenance, often warmth and food. The Vat serves to modify the Indigo molecule in such a way that it eschews inertness and chemically interacts with AKA dyes cloth (and other things, but for our purpose, cloth). The Vat must fulfill two conditions to properly modify the Indigo, it must first have an elevated pH, a condition know as alkalinity in which the amount of OH− ions exceeds that of H+ ions in the solution. Second, the Vat must be a reduced solution, meaning (in this case specifically) that the solution is devoid of dissolved oxygen and there are an excess of electrons in solution which causes the oxygen atoms present on the indigo molecule to be reduced (essentially snatching up these electrons into their orbit) and changing the Indigo molecule into what is called Leuco-Indigo which becomes dissolved in the Vat solution. This change is easily visually confirmed! Leuco-Indigo will appear as a transparent yellow-green (not too dissimilar from a childhood favorite soda, Mountain Dew) as compared to the opaque dark blue of Indigotin in suspension.
Once we have a properly reduced, leuco-indigo rich Vat, we can dip our cloth to dye with indigo. At the moment that the cloth emerges from the Vat it will be colored a tinge of green with the reduced leuco-indigo. As the piece comes into contact with the atmosphere, the pigment molecule, now adhered to the fabric, will lose its excess electrons and visibly transition back to blue.
There are many different ways of creating a Vat! There are many paths that will get you to the same finished product, a beautifully dyed blue piece! Each Vat style requires different ingredients and maintenance, and each has a set of positive and negative attributes.
The simple recipe that I advocate for the beginner is one that fits with our modern world (and is coincidentally one of the oldest know ways of producing a Vat). It is easy to make, requires no upkeep and (if properly sealed between uses) can be used on-demand for months at a time until it is exhausted of pigment. It is know as The Iron Vat. I've outlined the pros and cons for working with the Iron Vat below. If you have questions about this or any other kind of vat, feel free to get in touch.
Iron Vat Pros
• Simple Inexpensive Ingredients
• Can be saved and used over a period of months with essentially no maintenence
• Can easily yield a beautiful range of rich blues
• Is a cold (room temperature) vat. It does not require ongoing heating or re-heating in order to work properly. This is particularly crucial when dyeing with gluten resist, as a warmer vat will dissolve these materials
• Doesn't smell bad
• Great for cottons, rayons, hemps, ramie, linens, etc. Any cellulose fiber
• Perfect for shibori and stencil print dyeing
Iron Vat Cons
• Contains powders that can be inhalation irritants when dry and ingredients that are skin irritants in solution (though this is a fact of all indigo vats). Use of a respirator while working with dry ingredients and wearing gloves (not allowing skin contact with the Vat solution) mitigates these concerns.
• Not recommended for use by children. Contains soluble Iron.
• Not suitable for over-dyeing previously stained items, as the Iron can react with and may darken any impregnated tannins (coffee, tea, etc).
• Not suitable for protein fibers (wools and silks) as the excessive alkalinity can damage the fiber, making it brittle or scratchy feeling.
• Pieces MUST be rinsed between dips
• 50g Plant Derived Indigo Dye Powder (dark chalky Blue/Black/Purple in color)
• 100g Ferrous (II) Sulfate Heptahydrate (granular, pale green particles the scale of beach sand)
• 150g Calcium Hydroxide AKA Slaked Lime or Hydrated Lime (fine white powder)
• 50g Citric Acid
• Around 5 Gallons of water, the more pure the better
SUPPLIES, See Notes Below :
• Accurate Kitchen Scale
• 5 Gallon Bucket with tight sealing lid, no holes or cracks in the bucket itself
• Empty shampoo bottle with flip disc top
• 20+ Steel or glass marbles
• Stirring stick
• Rubber Gloves
• Measure out all ingredients and have them on hand, ready to mix
• Transfer the indigo powder into the bottle and add the marbles. Add just enough water to cover the indigo and shake for 2 minutes. We're talking vigorous cocktail shaking as opposed to a gently waking someone up shaking. This will hydrate the indigo making it more easily react in solution.
• Bring at least one gallon of water to a boil on the stove top in a stock pot. The volume is not particularly important as we are merely using it to make a condensed dye solution.
• Carefully pour the boiling water into the empty 5 gallon bucket (your Vat) and immediately add the Ferrous Sulfate, stirring until fully dissolved
• Add the Slaked Lime to the Vat and stir to mix until fully dissolved. The color should be a chalky green.
• Pop the top open on the shampoo bottle and gently spray the indigo suspension into the Vat. Add more fresh water back into the shampoo bottle and shake a bit more to rinse the marbles and spray that into the Vat, use up every little bit of that indigo powder! The Vat should now appear chalky dark blue.
• Stir and wait approximately 30 minutes. You will notice a reaction beginning to occur! The iron and lime will fall out of suspension, settling to the bottom of the vat and the indigo will react with the dissolved ingredients and as it becomes reduced (undergoing the molecular change to leuco-indigo) the Vat will change color to a transparent yellow green color with a distinct coppery purple surface.
• Top up your Vat with water (splashing as little as possible) until it is a couple inches shy of full. This should leave you enough room to add items into the Vat and not displace so much liquid that the Vat spills out and over.
• Your vat is now ready to dye in! The indigo reduction reaction is ongoing and the vat will continue to strengthen for another day at least.
NOTES ON DYEING PRACTICES:
• WET BEFORE FIRST DIP. Never introduce an item into the vat dry! Always wet (and massage the wetness into the core of the piece if it is already bundled or clamped) and wring any piece before it is placed in the vat for the first time.
• DIP MANY TIMES FOR DARK COLORS. Indigo dyeing is a cumulative process! You cannot achieve a dark saturated blue with a single dip! You must dip multiple times to build up an accumulation of transparent blue layers that together add up to a dark blue! Your dips into the vat can be rather short : 30 seconds to a minute is often acceptable. However, longer dips will impart more pigment onto the piece and allow the pigment to flow into areas tucked away between folds. If practicing shibori, massage your pieces under the surface of the Vat, easing pigment into folded areas for saturated blues right up to your ropes or block resist.
• NO SPLASHING IN THE VAT. Maintain the optimum dyeing conditions as long as possible with your Vat by introducing as little air as possible to it each time you dip your piece. Air contains compounds that are detrimental to the indigo Vat: carbonic acid which will lower the pH of the vat and oxygen which will convert leuco-indigo back into its non-reactive form, indigotin. Place the lid over your vat at every moment that it is not in use to minimize the interaction between the Vat and the air.
• GENTLY DIP & UNDIP. Slowly lower your piece into the Vat, disturbing the surface as little as possible. When removing the piece from the Vat, do your best to wring out the piece while it is still beneath the surface of the Vat. Squeeze it tightly before raising it through the plane of the surface of the Vat, then gently release your grasp as you raise, so that when it is above the surface, it does not drip.
• RINSE THOROUGHLY AFTER YOU DIP. Vigorously, with lots of bubbles and splashing, rinse your piece in fresh water. Then wring out the excess water from your piece into the rinse bucket (not the Vat of course) until it is as dry as you can get it. This vat style has gunky sediment. This can get trapped in the folds of a piece and can cause staining and uneven coloration. Once the piece emerges from the vat, it can be rinsed in water immediately, this will not remove any dye from the piece. I usually have a rinse bucket set aside as well to be able to dunk, shake and agitate my pieces between dips. Get any and all sediment off the piece before allowing it to oxidize.
• FULLY OXIDIZE BETWEEN DIPS. There is no set amount of time to wait between dips into the indigo vat. The only factor that you need to be aware of is the oxidation state of the indigo molecule that is attached to your piece. This is easy to recognize visually (unless you are blue-green colorblind, in that case, ask a friend). A piece that is completely oxidized will appear fully indigo colored, showing no green. The last areas to oxidize between dips are always those the most tucked away in the folds and creases of the piece. Make sure to rinse these areas fully and allow them to oxidize. Before attempting another dip, peel and pry your pieces open to peek into the crevices and make sure your piece is fully oxidized (no green). If you still see green, vigorously rinse your piece in water again and wring it thoroughly. The more dry your piece, the more quickly it will oxidize.
• KEEP ON DIPPIN. A fully saturated Indigo blue will appear nearly purple-black when wet. If you are trying to achieve a dark color, keep dipping beyond what you think is necessary. When the piece dries and excess pigment is rinsed off, the color will lighten substantially.
• STIR VAT AFTER USE. When you're finished dyeing your pieces, gently stir your vat and circulate all the materials inside, still no splashing! Put the lid back on the vat and store it away until your next dye session.
• RINSE BEFORE OPENING. If you have the luxury, I recommend rinsing your piece under your coldest fresh flowing water AS you are opening it. This will help you keep your whites bright and from any stray dye from adhering to parts of your piece that are exposed at this time.
• BALANCE THE PH. When your piece is completely dyed, it will probably have been exposed to a Vat with pH 11 or greater! In the long run, this can be detrimental to the pigment and the fabric. Thoroughly rinse this piece in water, starting with cold, gently progressing to warm until no more pigment comes off the piece. Next, dissolve a small portion of citric acid (say, a tablespoon per gallon of water) and let your piece soak in that solution for 20 minutes. This will reduce the pH and also will help to brighten the blues of the piece if there is any excess iron that came into contact with the fiber. Rinse.
• FIRST WASH YOUR PIECES ALONE. After balancing the pH, wash your pieces with a neutral detergent on their own in a cold water wash. If mixed with other garments during this first wash, there is the possibility that they will crock off, transfer color through rubbing against other pieces (I've tinted many a white shirt blue this way. After a couple washes and some time in the sun, they go back to bright white though!).
NOTES ON INGREDIENTS & SUPPLIES
INDIGO & SHAKER
Indigo pigment is available from a number of sources (soon to be from here!). But for the time being, I can recommend these three suppliers:
As a shaker bottle, I recommend just using an empty shampoo container. The disc cap is the best for getting the indigo suspension out of the bottle while keeping the marbles inside. I included a link below to show you exactly what I'm talking about. You really could get away with any plastic container that can be sealed and shaken. I've used glass marbles as agitators in the past but find that they can actually break when forced into contact with each other so much. No need to end up with little shards of glass at the bottom of your vat. In their stead, I recommend metal balls, which cannot break, but should be rinsed and dried after use.
VAT INGREDIENTS & Safety Gear :
You can often find both of these Vat modifiers locally at hardware stores or nurseries, though they may have additives and other chemicals mixed in. These blends are not suitable for Vat use. Below are pure, tested forms of the ingredients that work perfectly with this recipe. These are both powders that can cause irritation when inhaled. Always take care to protect yourself and your lungs when working with any dry powders. This is a good simple respirator and pair of gloves. Most any will be sufficient, but I've found that a tight fit on the respirator is important as is a long cuff on the glove.
All dye calculations are most accurately done by weight. I recommend picking up a little digital kitchen scale that is dedicated specifically to dye processes. I've tried many scales and this is by far my favorite. The price is just about as good as it gets for any kitchen scale and this one is 10 times more accurate that most comparably priced models. It is light, portable and takes 2 common AAA sized batteries.
This 5 gallon bucket is an ideal size for a starter Vat. Indigo vats like to be in deep containers with minimal surface area. This shape allows for minimal chemical interaction of the Vat with the atmosphere, prolonging the life of the ideal dye conditions. The dream shape is a tall column, the nightmare shape is a puddle. If you choose to use a recycled bucket, make sure that it is clean, has a tight fitting lid, no holes or cracks and a good handle to make moving it around as easy as possible.
GENERAL NOTES :
MAKE HEALTHY CHOICES - As with all dye processes, we're working with concentrated pigments, chemicals, hot liquids, heavy things. Each of these hazards can be dangerous to our bodies if we are careless with them. Make choices that protect your body for the long run : wear gloves when working with the Vat, wear a respirator when working with any powders, handle hot liquids carefully, be careful lifting that heavy thing, etc.
EXERCISE YOUR PATIENCE - Throughout this process there are so many appealing ways to cut corners and hurry toward results. Each one of them will compromise either yourself, your safety or the quality of the final product. Please do your best to avoid all shortcuts! You will certainly be more pleased with the final piece, which is what you'll have to hold after the process is through.
NO SUBSTITUTIONS - This is chemistry. Specific chemical reactions require specific ingredients to occur properly. Take time to prepare and acquire exactly what you need before beginning.