Name: Allan
Message: Have a a garment that has been dyed indigo dark blue made from cotton fabric. The dye has not been set as yet.  I would like to dye this garment BLACK.  Is this possible????, and how???

If you do not properly fix your blue dye, it is apt to come out later on. If the blue dye is truly indigo, and not merely indigo-blue, then it should have been fixed in the original application. If too much indigo was applied at a time, or if the chemistry of the indigo dyebath was incorrect, then it will be impossible to fix the indigo dye, and it will continue to rub off of the garment no matter how you fix any additional dyes.

Normally it is very possible to overdye a blue fabric to black. Black fabrics that you purchase may start off as any color, if for example the manufacturer made a mistake in dyeing. Any color can be overdyed to make black.

The best black dye for hand-dyeing cotton fabric would be a fiber reactive dye, such as one of the Procion or Remazol classes of dye, because fiber reactive dyes are very resistant to washing and are very easy to apply.

A black sulfur dye or vat dye is more difficult to apply, but can also be very washfast, and often quite resistant to bleaching and to fading caused by light.

If you use a black direct dye, it is important to use a cationic dye fixative, such as Retayne, to make the dye resist being washed out. Unfortunately, cationic dye fixatives often increase a dye's susceptibility to fading from sunlight, and they do not work on vat dyes such as indigo.