Below I have included the manufacture’s directions, along with the method I prefer. Mull them both over before starting, and see which works best for you.
Instant indigo is great for both small batches and large.
Simply mix with luke warm water. As the crystals dissolve the liquid will turn a murky "green" color. This is good! It means the dye is reducing.
Ideally, you will be adding just enough crystals to the water to dye a white cotton handkerchief a pale blue with one dunking. The more water you have in proportion to crystals, the thinner the solution. You will obtain a greater quality of color if you plan to dip your cloth into the indigo several times. While dipping once or twice, with a very concentrated vat, will give a beautiful hue, it will also have a greater tendency to crock, or rub off.
As with all powders, it is a good idea to take steps to avoid inhaling any of the indigo dust while handling the crystals.
Temperature is very important with indigo. Indigo works best when kept within the warm range. Try to keep your vat somewhere between 100 º and 120º F. A floating aquarium thermometer is a great help in monitoring the temperature.
Be careful while working (this includes mixing the initial batch), not to introduce much oxygen into the vat. This will tire the vat, keeping the indigo from binding to your fiber. If the vat does become tired, give it a rest. That is, leave it alone for a day, giving it time to compensate for the oxygen introduced.
How can you tell if your vat is tired? The surface of the vat, as it comes in contact with air should be a nice blue. However just below the surface it should be a rich blue-green. If the green disappears from within the liquid, your vat is very tired. If giving it a rest for a day doesn't do the trick, you may add a little Rit ® Color Remover (or thiourea dioxide, aka, thiox) to jump start the reducing process. However, if you add too much, it will strip the color off your cloth each time you dunk it into the vat (essentially re-reducing all of the indigo applied up to that moment); not a very fruitful process!
If you are dyeing yardage, it is often a good idea to dip only a few times, and allow the fabric to air for several hours or a day. This will allow the indigo on the fabric to fully oxidize, giving better color adhesion, and allow your vat to rest.
When you are through with your dyeing, rather than throw out the remaining liquid, try allowing the water to evaporate off. The remaining powder will make a very good indigo pigment.
SPECIFICATION DATA SHEET
Product: Indigo vat grains 60%
Chemical Formula: C6H4CONa(NH)C:C(NH)CONaC6H4
C. I. Number: 73001
Molecular Weight: 308
Physical Appearance: dark blue grains
Fineness: 8 mesh to 4 mm
Moisture: < .5%
Quality Control: analytical test & dyeing test
No toxic effects known from dust inhalation or ingestion. Inhalation may cause coughing or sneezing. Avoid breathing dust. Avoid contact with skin or eyes. Wash thoroughly after handling.
NFPA Ratings HMIS Rating
Health 2 1
Flammability 1 1
Reactivity 0 0
4 = extreme 3 = high 2 = moderate 1 = slight 0 = insignificant
METHOD OF DYEING WITH VAT INDIGO 60%
Dyeing with indigo grains is a cold water process. The temperature of the dye bath should be between 68 and 78 degrees (20 º to 24º C).
Add to dye bath vat the following:
indigo grains 1.0 Kgs
caustic soda flakes 0.2 Kgs
Sodium Hydrosulphite of soda 0.8 Kgs
Mix with ten liters of water. Add 1 to 2 Kgs calcium carbonate to the dye bath for dipping clothes. Fabrics should be dipped two or three times for a dark color.
(caution: creating a dye vat at this concentration will lead to heavy crocking! -JM)
HANDLING, STORAGE, AND SHELF-LIFE
Keep bag closed to prevent moisture absorption and contamination. When the product is stored in an unopened container at a temperature range between 65 º and 104º F, the shelf-life of this product should exceed one year from date of purchase.
The crystals will last much longer in a dry environment. So if you live in a very humid climate, think about keeping it in your freezer (freezing often draws moisture out of things, causing “freezer burn”. In this case, freezer burn is a good thing!