Indigo - the queen of dyes

The method described below uses Indigo VAT 60% Grains which is a pre-reduced Indigo needing much less caustic and Hydros to produce the amber 'Leuco Form' used for dipping the fabric.

The following will make a 'mini vat', but the proportions can be multiplied up to the desired quantity.

15gms (2tbsp) INDIGO VAT 60% GRAINS
15gms (1tbsp) Caustic Soda Solids (prills) Available from hardware stores
NB: 60gms Washing Soda can be substituted for 15gms Caustic Soda
10gms (2 'mean' tsp) HYDROS (Hydrotherm DD)
5 litres Water
A container that will allow for 5 litres of water, plus fabric, plus movement
(a household 2 gallon bucket would be fine)
A piece of cling-film larger than the top of the container.

Making up the Indigo vat

Fill bucket with 5L water at 25°C (Hint: to achieve this temperature, put 5L cold water in bucket, remove two cupfuls and replace with two cupfuls boiling water)
Add 15gms Caustic Soda. Stir well to disperse evenly.
Sprinkle 10gms Hydros onto the surface and stir slowly.
Add 15gms Indigo grains slowly in small amounts and stir gently - avoid making bubbles.
Cover the surface of the liquid immediately with the cling-film to stop air entering the liquid.
Leave for 1hr by which time the Indigo should have fully dissolved leaving a clear greenish-yellow solution indicating that the Indigo is fully reduced.

Dyeing the fabric

Add wet, pre-washed fabric/yarn. Making sure the fabric is fully submerged, move the fabric in the liquid to ensure it is fully impregnated. Allow up to 2 minutes for this procedure.
Remove fabric/yarn from the Vat and squeeze excess liquid back into bucket.
On exposure to the air, the Indigo will begin to oxidise and begin to turn blue. If the colour is too pale, re-submerge into the Indigo Vat and repeat Steps 1 & 2. This technique can be repeated several times to 'build up' the colour on the fabric.

Once the desired colour is achieved, the fabric is rinsed in cold water and then given a hot wash with liquid detergent.

Trouble-shooting

The Indigo Vat can be stored if kept airtight
When made up, the indigo dye should be clear greenish yellow.
If green, add small amount of hydros until it turns greenish-yellow again.
If cloudy, add more caustic soda.
If pale & watery, it has gone off and should be discarded.

Health & safety

Caustic Soda and Hydros are corrosive chemicals which will cause burns to the eyes and skin. Safety spectacles, rubber gloves, dust-mask and protective coat/apron must be worn when handling. Work in a well ventilated but draught-free area. DO NOT USE THE SAME IMPLEMENTS OR CONTAINERS FOR DYE PREPARATION AND FOOD PREPARATION.

These instructions have been adapted & refined by Delia Copland based on information from Kemtex and Kate Wells.

Indigo dye and an Indigo Starter Pack are are in the Fabric Art section of our catalogue, on page 28: take me to the catalogue download page...