Vat dye
From Freepedia
Vat Dyes Vat dyes are an ancient class of dye, based on the original natural dye, Indigo, which is now produced synthetically. Both cotton and wool, as well as other fibers, can be dyed with vat dyes. Not all vat dyeing is done with vat dyes! "Vat dyeing" means dyeing in a bucket or vat. It can be done whenever a solid even shade, the same color over the entire garment, is wanted, using almost any dye, including fiber reactive dye, direct dye, acid dye, etc. The opposite of vat dyeing is direct dye application, such as, for example, tie dyeing. "Vat dyes" are a special class of dyes that work with a special chemistry. About Vat Dyes Most vat dyes are less suitable than, say, fiber reactive dyes, for the home dyers, as they are difficult to work with; they require a reducing agent to solubilize them. The dye is soluble only in its reduced (oxygen-free) form. The fiber is immersed repeatedly in this oxygen-free dyebath, then exposed to the air, whereupon the water-soluble reduced form changes color as oxygen turns it to the water-inoluble form. Indigo is an example of this dye class; it changes from yellow, in the dyebath, to green and then blue as the air hits it. Instructions for dyeing with vat dyes PRO Chemical & Dye, which sells some vat dyes, provides instructions online for Immersion Dyeing using PRO Vat Dyes. The process requires the use of lye (sodium hydroxide), which must be used with due care, including the use of goggles. Indigo is subject to major crocking (rubbing off of the dye onto other items) unless it is applied carefully. This means use a weaker dyebath, and dipping many times, rather than a single strong dipping.
Light-oxidized Vat Dyes Ink-o-dye is a type of vat dye which uses light rather than oxygen to 'fix' the dye, with a inspirationally wide variety of possible effects. These are a type of dye which is chemically similar to vat dyes, but instead of being applied in an oxygen-free bath and being developed in the fabric by exposure to oxygen, Inkodyes are developed by light. Inkodyes are true dyes, not fabric paints. (A dye actually itself attaches to the fabric; fabric paint includes a glue-like binder, which imparts a stiffer feeling to the fabric.) The process is more difficult than the process of tie-dyeing with fiber reactive dyes. One retail source of Inkodye is Dharma Trading Company. Jean Ray Laury's book, Imagery on Fabric, provides information on how to use this type of dye, as does Dianne Epps' book, The Chemistry of Vat Dyes
