Calculating Amount of Indigo Needed

Q: Is there a way to calculate the quantity (weight) of fiber I'm gonna be able to dye with a given quantity of indigo?

A: Potentially... There are so many factors though including the fiber type, weave or knit structure, fiber weight, concentration of the indigo pigment, reduction type and reduction state, depth of shade and amount of coverage.

I think it would be more of a thing where you dye some fabric just the way you like it and then develop a recipe based on first results. It would be challenging to be predictive about it...

Dyeing Protein Fibers in a Natural Indigo Vat

Q: I’ve heard I cannot dye protein fibers like wool or silk in an iron vat, is that true?

A: You CAN use the iron vat for protein fibers, but when I do, I make sure that I do two things:

First, I make sure that the fibers NEVER touch the sediment at the bottom of the vat. The sediment contains a lot of iron which will bond to the protein fiber and cause the indigo to look dull and flat.

Second, I make sure that I rinse my pieces in acidic liquids immediately following each dip. Water with a little citric acid powder (half teaspoon per gallon) or a quarter cup of vinegar for about 4 gallons of water, works well. Ferrous vats have a high pH and animal fibers prefer a low pH. The high pH of the vat will break the protein chain and the fibers will feel scratchy or lose their luster if they are allowed to dry after coming out of the vat without being rinsed in an acidic bath first. I also soak protein fiber pieces in a mild vinegar solution overnight after dyeing and prior to washing. I’ve also heard, though never done this myself, that a little hide glue added to the vat will help keep the fibers in good shape.

If dyed properly, a ferrous vat will create beautiful blues on protein fibers. The ideal vat style for protein fibers is the traditional fermentation vat which is fed by decomposing plant matter, wheat bran and oxygen (from stirring) but is very challenging to execute on your own without guidance or experience. You can also look into a fructose vat or thiox vat for other options. Maiwa has a great PDF on different vat recipes here: https://naturaldyes.ca/indigo-pdf.

Dyeing Stretch Fabric with Natural Indigo

Q: Can I use a natural indigo dye vat to dye stretch fabric?

A: It really depends on what you mean by "stretch". The characteristic of the weave or knit is less important than the fiber content itself. You'll get better color uptake on materials that are higher percentage natural fibers, but I've used fabrics that are 50/50 cotton/poly and gotten decent results, about only 50% saturated compared to a full cotton. If you're using something that's like 92% cotton / 8% spandex you wouldn't really even be able to discern the difference in color uptake than with 100% cotton.

Ferrous Vat Longevity

Q: I just purchased one of your Natural Indigo & Shibori Dye Kits. Once I create my indigo vat, do I have to use it right away or does it last for a while?

A: Your vat will last for weeks, once mixed up, if never used. The key to longevity of a ferrous vat is to minimize its contact with air. You should always keep it tightly lidded when it is not in use. And, when you're using the vat, make EVERY EFFORT to not slosh, splash, or drip back into the vat as that will oxidize your vat and leave the indigo pigment unable to bind to fabric. The kit is designed so that the pigment and the ingredients that activate it, should exhaust themselves at the same time.

Once you begin using your vat and it starts to lose potency, you can always rejuvenate it. I go in depth on the process of sharpening your vat on my page about indigo vat basics.

Shelf Life of Natural Indigo and “Pasting-Up” Your Powder

Q: I purchased some indigo dye several years ago and the label on the jar says it is 100% natural indigo and to use within 12 months. The contents are in large chunks. Must I throw it out or is it still useable?

A: Natural indigo is a stable pigment and has no set shelf life. As long as it is kept cool, dry, and out of light, I believe it can be used in perpetuity... I've used pigment that is many years old with no ill effects.

The chunks themselves will actually present you with a larger problem! Indigo needs to be "pasted-up" before use. Pasting up involves hydrating the indigo and getting it evenly dispersed in a pasty suspension. If you don't properly do this, you'll end up with chunks of pigment in your vat that will either be wasted or smear onto your fabric. A nice way to begin the “pasting up” when your indigo is in dried chunks like yours, is to run your chunks through a coffee grinder (though this creates a lot of dust). From there, I put the pigment into a plastic bottle with a bunch of pebbles and add just enough water to turn it into a thick/syrupy paste and SHAKE. I don't have a set amount of time to tell you here, but just know that you can't overdo it. This will make sure that the indigo is all broken up and available to be dissolved in your vat. Pour the resulting paste into the vat and rinse the bottle and pour the rinse in as well as many times as it takes until the stones and bottle rinse clear. From there you can use any vat recipe you prefer!

Toxicity of Indigo and Indigo Dyeing

Q: What is the toxicity of the indigo dye you sell? Would it be okay to use it to dye a cutting board made of wood?

A: The indigo I sell would be safe to use to dye a cutting board in terms of toxicity (although, important to note this is not true for all indigo dyes as many indigo dyes on the market - even those labeled “natural” - are produced using toxic chemicals).

So, while it would be safe to dye a wooden cutting board with the indigo I sell, I do want to caution that indigo is not a particularly "penetrating" dye. It will only dye the surface layer of the wood and if that is disturbed (cutting, sanding, chipping), the un-dyed areas below will be exposed.

Indigo and Splatter Dyeing

Q: Can I use a paint brush or toothbrush to splatter dye with indigo?

A: Splatter dyeing doesn’t work for indigo because of a particular quirk in how the dye is activated. To actually get the dye to adhere to fabric, it needs to be in a “reduced” chemical state. The action of splattering the indigo exposes it to lots of air and oxygen and makes it essentially inert before it hits the fabric. The blue flecks would stain the fabric but after a couple washes and some time in the air, the color would fade right off. To get the color onto the cloth the pieces have to be immersed in the dye.

Indigo and Cotton Velveteen

Q: Is cotton velveteen suitable for dyeing with indigo?

A: Yes, that should dye very well!  Natural indigo works well on natural fibers from plants or animals. 

Because cotton velveteen is a thick and very absorbent fabric, be sure to exit the vat very slowly to give it adequate time to drain back into the dye pot between dips. Otherwise, it will act like a sponge and carry a lot of the vat liquid out with it. Don’t wring/drip through the air. Best to wring the piece out while it is still under the surface of the vat and then raise it up and out, then release the tension.

Indigo and Polyester

Q: Can I dye polyester fabric using natural indigo dye?

A: Natural indigo vats do not effectively dye polyester.  It seems the indigo pigment molecule doesn’t have a way to properly bond to polyesters.  I’ve gotten blue-greys dyeing polyester in the past but they don’t look great and are never that saturated and tend to wash and sun fade very easily.  Natural indigo works best on natural fibers from plants or animals.  You will even notice that if you dye a garment that is made of natural fibers (say, cotton) but is stitched using polyester thread, the fabric will dye but the thread will stay more or less white.

Over-dyeing with Indigo

Q: I spilled paint on my dress. I’d like to dye it to a nice dark blue. Can I use indigo to dye over everything?

A: I wouldn’t hold out much hope for a natural over-dye solving a paint spill problem as natural dyes won’t bond well to synthetic materials (paint/plastic). Your fabric may get darker, but the places where the paint are would more than likely stay the same color.

Is Indigo Dye Okay for Sensitive Skin, Is it Safe Enough to use on Baby Clothes?

Q: Is natural indigo safe to use on baby clothing and accessories? I was hoping to dye some onesies and swaddles with the indigo.

A: In all my years of experience researching and working with Indigo, I have never heard of any allergies or even cautions for humans for any age regarding the natural indigo pigment molecule. The kits have been used at many a baby shower and dyed countless onesies, blankets and sheet sets.

Light and Pale Shades of Indigo

Q: What is your recommended amount of indigo for a five gallon vat if I wanted a pale blue, not a dark blue?

A:  The kit comes with a bottle containing 50g of indigo extract. This is plenty to make a very saturated blue dye achievable with only a half dozen dips or so. If you would like a paler blue, it is best to get there with the same number of dips, though each dip will only be a baby step toward deep indigo as opposed to using the full strength of the vat. So, you can mix up the vat as normal (same amount of water, all the iron, all the lime) and simply add 1/4 of the indigo. This will produce a weak vat. When you layer many dips in this vat, you'll get some wondrously rich pale blues. You can save the indigo for later addition or for another vat.

Fixing Indigo Onto Fabric

Q: How do I set the indigo dye?

A: Quick answer : Air and something acidic.

Long answer : Indigo is a vat dye. The pigment molecules adhere to the fabric when they are in an elevated pH and chemically reduced (devoid of oxygen molecules in this case). When the fabric is reintroduced to the chemicals in our atmosphere (namely the oxygen in air) it oxidizes, turning from leuco-indigo to indigotin by incorporating oxygen. The when entirely blue, the piece then needs to be rinsed of all excess pigment and submerged in an acidic bath. The Indigo & Shibori Natural Dye Kit includes a packet of citric acid which can be used to create a rinsing bath for your work. Citric acid in water is historically called a "Sour Bath." This sour bath will bring the pH of your goods down from the pH11+ conditions of the indigo vat. Many other acids can be used including vinegar, lemon juice (essentially liquid citric acid), or strongly steeped black tea.

For longevity of your dyed goods, a soy post-treatment can help to protect from wear and UV exposure, see the Q&A for Sun Fading of Indigo for more information.

Materials and Fabrics Suitable for Indigo Dyeing

Q: Is cotton a good type of cloth to dye? Are certain fabrics more suited to indigo dye than others?

A: Yes, cotton would be great! In fact, the bandana that's included in the kit is 100% cotton.

The indigo vat style provided in this natural dye kit is know as the iron vat and contains ferrous sulfate and lime, both of which can be damaging to finer protein fibers like wool and silk. If you would like to dye with protein fibers, make sure to avoid the sediment which settles at the bottom of the vat. If you make contact with the sediment, thoroughly rinse your piece as soon as possible. As soon as you are finished dyeing any protein fibers, before they have had a chance to dry, make sure that you THOROUGHLY rinse in cold and warm water and pH balance them. I recommend a prolonged soak (half hour or so) in a solution of 1/4 cup vinegar (any 5% acetic acid variety will do) to one gallon of water, agitating occasionally to restore the pH of your item to slightly acidic.

All plant based fibers work exceptionally well in this vat style, that includes bamboo, cotton, hemp, linen, ramie, rayon, etc. And as you'll see when using the clamps included with the kit, even wood dyes very well! These cellulose based fibers are more amenable to dyeing in the alkaline conditions of the indigo vat. When you’ve finished dyeing with them, do make sure to pH balance as well though, using the citric acid included in the kit.

Synthetic fibers like polyester, nylon and nylon, rubber, neoprene, etc. do not dye well.

Disposing of a Ferrous Indigo Vat

Q: How do I dispose of my indigo vat?

A:  Your natural dye kit indigo vat contains these three ingredients : Indigo Pigment (an organic molecule), Ferrous Sulfate (100g) and Hydrated Lime (150g). Both of these compounds are traditional soil amendments for trees and lawns.

There are two recommended methods for disposal, both start with this step :

When your vat is exhausted (you've pulled all the pigment out that you can) whisk air into the vat (a huge no-no when you're trying to dye). This will introduce Carbonic Acid (dissolved Carbon Dioxide) into the solution, neutralizing the pH and converting most of the Lime to Gypsum.

1) If you are on a septic system : Do not dispose of any liquid down your drain, instead, dilute your vat to 1/4 strength and disperse evenly on a lawn or the ground at the base of trees and shrubs. If you have iron deficient soils, this can help green your plants (http://homeguides.sfgate.com/add-iron-garden-soil-95549.html)

2) If you do not have available green space, or are on a municipal sewage system : Allow your whisked vat to settle out. Pour the opaque blue liquid down the toilet being careful not to allow sediment to flow out. Dispose of the remaining chalky sediment in the trash.

Large Container e.g. Trash Can Vat

Q: I have had great results working in a 5 gallon container but want to be able to dye yardage and large pieces. I've never dyed in a larger container. Can I use a large trash can (32 gallons)? Do the proportions simply need to be multiplied by 6 to account for the size?

A:  Essentially, yes! To work in larger dye vats, you must scale up the amount of each of the vat ingredients to get it to behave similarly on the larger scale. You're leaving the realm of working with kits when you start using containers larger than 10 gallons. Take a peek at the page on my website that goes more in depth on creating your own indigo vat from scratch : Indigo Vat Basics

Dye Vat Capacity

Q: The kit indicates the vat can manage about 5 pounds of items. Can you tell me if that number changes if you are dipping items for longer or more times? So if you dipped 5 pounds of tea towels (for example) 3 times each, would you plan to dye 2 1/2 pounds of tea towels, if you were going to dip them 6 times each?

A:  You’ve got it. The darker you dye your items the less total weight the vat can accommodate. Also, the lighter weight your fabric, the less weight the vat can dye. Also, how well you treat your vat contributes to how much material you can push through it. Also, if you tie your pieces up into small bundles so only the surface gets dyed, you can dye more total weight (with the same amount of surface area). The 5lb measurement is really subjective!

Lightweight fabric has more surface area relative to the total weight of the fabric so actually absorbs more indigo per pound than a thick, heavy weight fabric (which has a much smaller surface area). Thin fabrics can be very taxing on a vat, so the yield per weight numbers don’t really apply to to them. The 5lb weight notation on the kit was initially tested using a medium shade of blue, dyed with shibori patterning that was about 50/50 indigo coverage to undyed fabric on medium weight cotton jersey.