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Organic Indigo Vat

Organic Indigo Vat

This is the recipe for the vat I use in my workshops, is an organic vat to reduce the indigo through fermentation. 

1 part natural indigo
2 parts calcium hydroxide, also known as pickling lime, cal, calx
3 parts fructose crystals

Indigo quantity
- 25 grams (about an ounce or 2 tablespoons) of indigo will make a vat that will dye about 1 kg (2.2lbs) of fiber a light to medium shade of blue.
- 50 grams (about 2 ounces or 4 tablespoons) of indigo will make a vat that will dye about 1 kg (2.2lbs) of fiber a medium-dark shade of blue.
- 100 grams (about 4 ounces or 8 tablespoons) or indigo will make a vat that will dye about 1 kg (2.2lbs) of fiber a dark blue, and there will be enough indigo left in this vat to dye other items a slightly lighter shade, too.

Other materials and tools
Plastic gloves
Hot water
Large Mason jar
Wooden spatula
Mortar and pestle
Dye pot
5 gallon bucket with a lid

1. Create your stock in a large Mason jar or a sturdy plastic container. A jar is nice so you can see the reaction take place. You will be adding hot water, so make sure the plastic is heat resistant.  I made my stock with 32 grams (approx 1.2 ounces) of indigo in a litre Mason jar. If you are making anything larger than that, you’ll need a larger container to mix the stock.

2. Wet out the natural indigo with a little warm water, use the mortar to form a paste. When ready pour it in the jar and add about 2 cups of hot water (120°F or 50 C) and stir. The solution will be dark blue and a bit gritty.

3. Add the fructose crystals and stir well.

4. Carefully add the calcium hydroxide and stir well so that the calcium hydroxide is incorporated into the mixture. Work out any lumps but try not to beat it so much that you add a lot of air into the solution. Top off the jar with additional hot water once the calcium hydroxide is incorporated.

5. The solution should now look greenish yellow and somewhat murky. Let this settle for an hour. The chemical reaction will work more quickly if the solution is warm, so you can place the glass jar in a pot of hot water. Then stir the solution every 15-20 minutes three times. Observe the stock, you can see the liquid near the top is getting clearer and yellow-green – don’t worry if it turns brownish red, that’s okay too. After 45 minutes have elapsed, give the stock a final stir and let it settle. I recommend leaving the stock overnight, others dyers use it after an hour. 
The stock is ready to use if it has the characteristics described below:
- There’s a nice dark blue indigo flower (blue foam) on the top of the jar of solution and a layer of coppery scum as well.
- There’s a clear demarcation between the liquid in the vat and the layer of sludge below.
-The color is a yellowish green (it will look somewhat opaque – different than the startling clearness of a chemical vat).  Note that depending on your indigo, you might also see a brown colored stock.

6. Fill a non-reactive dye pot (pewter, clay or stainless steel) about 2/3 full with hot water – approximately 120°F or 50 C.  Carefully tip in the contents of the stock solution including the sludge at the bottom. Stir gently and allow the vat to come to a yellow-green color (this takes between 15-30 minutes).

7. All fibers should be thoroughly soaked (wetted out) in lukewarm water prior to dipping.

8. When you see that the vat has become yellowish-green and there’s a blue flower and some coppery scum on top, the vat is balanced and ready for dipping. Dip your wetted out skein, fiber or fabric into the vat and keep it submerged for 30 seconds to 15 minutes.  Carefully remove the fiber, letting the excess liquid drain into a drip bucket that will be returned to the vat. You will begin to see the fibers turn from murky green to teal to blue. 

9. Allow the fiber to turn blue with no teal or yellowish areas. Let the fiber air for at least 1 minute, opening up skeins if the yarn strands are stuck together or unfolding corners of fabric.

10. Continue dipping until the fiber is two shades deeper than what you want. As the fiber is rinsed and dried, some of the excess indigo is washed away and the fiber turns out lighter than what you see coming out of the vat. If you are attempting to match an indigo shade from a swatch, dampen the swatch for a more accurate match.

The Drip Bucket
Since indigo is precious, you can return the collected indigo liquid to the vat. Plan on doing this when you take a break from dipping or need to replenish the vat.

Rebalancing the Vat
The vat will need rebalancing when the dye liquid turns blue. At this time, reheat the vat gently to 120°F or 50°C and add a generous spoonful of  fructose crystals. Wait 15-30 minutes for the vat to return to a yellow-green state. If it remains blue, add a level spoonful of calcium hydroxide, stir and wait. You may need to repeat this process for the vat to reduce.

Replenishing the Vat
The vat may be replenished with additional stock solution if you make a new batch and add it to the existing vat.

Storing the Vat
You may keep the vat by transfering it to a 5 gallon bucket with a lid. Label it and use it within 6 months. You will need to rebalance it the next time you use it by reheating it and adding additional fructose and calcium hydroxide.

Disposing of the Vat
Modify the vat’s pH by adding 1-2 cups of white household vinegar and disposing the cold vat down the drain and throw the sediment away, as it may clog the tube.

Have fun!