Why do people use synthetic indigo dyes instead of natural indigo dyes nowadays?
There are still people who use natural indigo dyes stuffs. Woad is one source plant, and Indio plant is another. Woad takes a lot of material to made that fine blue, and it is a multi step process, same with idigo plant, though less plant matter is needed to get the same amount of indigotin. The process of dyign with natural dye indigo is quite striking, and the color change is amazing to say the least. Mostly is it time consuming, and less convenient than opening a box or bottle and hucking it into the bin with the fabric.
Synthetic indigo is chemically identical to natural indigo dye. The reason why people use it is because it is less expensive to make from petroleum than it is to grow it in plants. Dyeing with indigo is a complex process, whether the indigo is synthetic or natural. The indigo dye is a vat dye, and must be dissolved in lye and applied in a dyebath with chemicals that remove oxygen and create a reducing environment. The dissolved form of the indigo is yellow in color and can get inside the fiber simply because it is dissolved; then the fabric is removed from the dyebath, and the indigo oxidizes back to insoluble blue in the air. You can apply only a small amount of indigo at a time, as applying indigo all at once, in too concentrated a from, results in dye sitting on the outside of the fiber where it easily rubs off. Applying indigo by dipping the fabric many times in the dyebath gives results that do not rub off. Indigo is a wonderful dye, but applying it is not a job for beginning dyer
