When we last talked Indigo I was wondering why my native indigo fermentation vat had carked it.

Since then I have been testing out a few theories and approaches in the hope that I could get a local vat recipe that was more reliable. This kind of vat is worth the effort, as it is devoid of harsh chemicals and can be disposed of safely.

I was very lucky to have the help of two very useful people in this mission, Trudi Pollard, of local natural dyeing studio Pollard Designs, and Tracey from One Thing at a Time, whose chemistry brain has been invaluable.

indigo dip day trudi

We tried the honey lime recipe on all the indigo varieties we could get our hands on:

  • French indigo powder
  • Japanese Powdered
  • Japanese slurry ryukyu
  • Dried local Japanese indigo leaves
  • Dried native indigo or indigofera australis
  • Organic powder from Kraft Kolour

Fermentation vats are no difficult to set up but do take a little patience to get right for your local area and products.  So far, the 1-2-3 ratio has not worked for me, but I have used that as a starting point for considering potential quantities.

indigo dip day trudi

Local Water Quality

Here in Perth our mains water can vary greatly in composition season to season, so to avoid this we used rainwater.  That said, even the rainwater used varied from a pH of 5 to a pH of 8 from different tanks.  The lesson here is to test your water pH first and foremost.

Sourcing Lime

If you are looking to source lime for an indigo vat, you need to find calcium hydroxide or Ca(OH)2.  Most lime products on the market are for building and may contain a combination of calcium carbonate and surfactants, neither of which you want in your vat.  Go straight to a chemical supplier and ask for the Materials Safety Data Sheet (MSDS) , and ask specifically about surfactants.

The lime I would recommend for Perth is from Lime Industries, 43 Hector St, Osborne Park. The lime putty or the envirolime will work in an indigo vat, and are wholly WA made.

Lime Solubility

Be aware that the form of your lime will lead to it reacting different in your vat.  We sourced a liquid form of lime called lime putty, and it needed a lot less lime for the same result in comparison to powder. Pellets again will be a different story.

Indigo Forms

Indigo can be fermented fresh, dried, powdered or from a slurry.  Typical recipes are for powdered indigo so do not be afraid to increase the amounts for other types of indigo accordingly.   Other forms of indigo may also need 4-10 days to ferment so allow your vat time to mature.



I chose honey as a base for my vat, which, whilst more expensive, was more predictable in behaviour.  That said, even honey can vary in pH widely depending on the location of the hive, the pollen and the time of the year.  Given this, fermented fruit may not be as bad as I thought!

Balancing the Vat

The ultimate aim is to balance the vat using your honey and lime to get to a pH of between 9-11.  Depending on your starting pH and what you are adding in, your quantities can vary widely.  So my number one piece of advice is to take it slow, and test at each stage.  I think stopping when the pH reaches 9 and waiting half an hour is a good approach too.

Fold in the Egg Whites

Tracey suggests that you use a method similar to folding batter into egg whites when adding the lime.  Take a little out of the vat, dilute the lime mixture, slowly add it back in.

Start out Small

Making a small trial vat wont hurt anyone, and if you get it right, you can add it to a large vat later.  Because, after all, indigo is liquid gold.

indigo dip day trudi

If you have never used indigo, I hope the pretty pictures entice you a little!

Has anyone else got any top tips for making a fermentation vat? Did you have similar problems pop up or widely different?