If you’ve dyed with indigo for any length of time, you may have come to the point of needing to do indigo vat troubleshooting. There are four or five standard issues that can arise with the indigo vat. These are normally easily fixed. The most frequent troubleshooting tactics involve the pH, or the vat temperature.
Natural dyeing with indigo is both a simple, and a complicated process. The procedure is simple, but what happens on the molecular level is complicated, and a single missing part can ruin the vat. Or at least, it can ruin the vat until you know how to fix it.
If you are new to dyeing with indigo, you can check out this article for the basic reduction vat method based off of a woad extraction. For an easy reduction vat with powdered indigo, or woad indigo, check out “Creating a Natural Indigo Reduction Vat.” You can also do a natural fermentation vat, or create a Saxon Blue vat. The Saxon Blue method is detailed in Indigo, Madder, and Marigold by Trudy Van Stralen, this method should not be used anywhere near children.
These trouble shooting tips are designed for the basic reduction vat. Some problems with the natural fermentation vat can also be solved with these methods. 
Indigo Vat Troubleshooting One:
The Indigo Vat Liquid is Blue
A reduced indigo vat should be green, with a blue to purple foam on top. If your vat is blue then there is a problem. Start by checking the pH and make sure it is at 10. Then, check the temperature of your vat. It should be at least body-temperature or warmer. If it feels cool, then heat it up on the stove or outdoor burner, just make sure it doesn’t boil as that can damage the reduced indigo. Once your vat is at the right pH, and is the right temperature, the reduction reaction should happen very quickly.
If the vat does not change despite adjusting the pH and heating up the vat, you may need to add more reducing agent. Add an additional teaspoon of the reduction agent, and let sit for 10-15 minutes. This should reduce your vat.
Indigo Vat Troubleshooting Two:
The Fabric Color Isn’t Darkening
If you are dyeing yarn or fabric and the fabric is refusing to go past a certain depth of shade, then there could be two possible problems. The first is that you have put the fabric into the vat, and left it. In this case, the indigo only lays down to a certain depth of shade before the molecules start being re-reduced and removed from the fabric. For the darkest indigo, you need to soak, or vat, the fiber for 15 minutes. Remove the fiber and oxidize it for 15 minutes, and then revat for a further 15 minutes. Continue this rotation for 4-8 rotations of vatting and oxidizing for the darkest and most colourfast indigo blues.
A second option is that there is too much reduction agent in the vat. In this case, you are following the correct dye procedure, but the fabric isn’t darkening. To remedy this, leave the lid off the vat for half an hour to an hour. If the vat cools in this time, warm it up again. After an hour, some of the reduction should have worn off and it should no longer be stripping the dye from your fabric.
Indigo Vat Troubleshooting Three:
My Fabric Color Isn’t Blue
This situation is most likely to occur with a woad indigo extraction turned dye vat, than from a standard indigo reduction vat. However, if you leave your indigo reduction vat for a few days you could have color issues, or if you are doing a natural fermentation vat.
If the fabric remains green when it oxidizes, a typical happenstance with woad, the remedy is simple. After you are finished with the dye process, let the fiber or fabric oxidize overnight. Then, rinse in vinegar. The pH change will turn the color of the fabric to blue. If you do not change the pH, the green remains permanent, as long as it never encounters anything acidic.
If the fabric is grey or purple when it oxidizes, your pH is too low and the indigo is not properly reduced. Indigotin reduces at a pH of ten, if your pH is lower than the indigo will not adhere to your fabric. Check your vat’s pH, and add washing soda to bring it back to a pH of ten. You can then re-vat your miscoloured fabric and it will pick up the indigo and be fine. Alternatively, you could keep it in as is, as those non-blue indigo colors are also colourfast.
Indigo Vat Troubleshooting Four:
My Indigo Is Splotchy
If you have uneven indigo dye coverage, it is probably caused by your fabric or yarn floating in the dye bath. Use a few non-reactive metal spoons, or pvc pipes to help hold your material under the dye vat. You can also deliberately move material through the vat to encourage an even dye coverage. In the woad vat, this floating can cause pink or purple splotches to form which cannot be over-dyed.
One other cause of splotchy dyeing is residual oils, detergents, and waxes that remain on the surface of the fabric. These compounds act as resists and prevent even dye coverage. Always make sure to wash material in warm water, with soap, and rinse thoroughly before dyeing the fibers.
Also, always thoroughly soak and saturate fibers in clean water before introducing them to the dye vat. Dry fibers will take up dye unevenly, which can contribute to splotchy dyeing as well.
Indigo Vat Troubleshooting Five:
My Indigo Washed Out
There are several reasons that indigo may wash out of your dyed fabric. This symptom is most common with cotton, but can happen with wool as well. Usually it is caused by trying to do too much, too quickly and being impatient.
First, your vat could be too strong and trying to lay down too many molecules at once. The second, which usually happens in conjunction with the first, is that the fabric is being left in the vat for too long. The third cause is that the fabric is not being oxidized long enough. Fourth, the material might only be being vatted and oxidized once, or only a few times. These four symptoms together cause the indigo to wash off your fabric, leaving a dark blue fabric looking light blue instead.
To fix it, follow your vat and jar preparation instructions exactly. Let the vat fully reduce. Make sure your material is wet before introducing it to the vat. Only leave fabric in the vat for 15 minutes, never longer. Remove and let your material oxidize for a full 15 minutes. You can have two sets of material alternating in the vat so that you are not waiting too long. Fabric should be vatted and oxidized a minimum of 4 times. The only exception to that is a short, singular vatting for over-dying purposes, or to exhaust a mostly used indigo vat.
Woad Indigo Vat Troubleshooting Bonus:
When dying directly with a woad indigo extraction vat, always double or triple check the pH. You can let a woad indigo vat sit, but it may cause the pH to go closer to neutral as the vat starts fermenting. If this happens, a quick addition of washing soda, and a pH check will restore the blue of your vat. Of course, if you want reddish, greenish, or other tones from your indigo vat, you can always reduce it at a lower pH than recommended.
Back To You:
Have you successfully done indigo vat troubleshooting? Have you had a challenge that I didn’t cover here, or do you have another question on dyeing with natural indigo, or natural woad indigo?
Leave a comment, I enjoy hearing from you!