Over-reduced Vat: An over-reduced vat is when you have added too much reducing agent. If the pH is too high, add a mild acid such as distilled white vinegar. To raise pH, add a small amount of calcium hydroxide to the vat, stir and wait for the vat to balance. If your pH is too low, the chemical reaction in your vat will not be efficient and may affect the color. This pH level is moderated by calcium hydroxide. PH: The indigo vat is dependent upon a moderately high pH level between 10 and 11.5 for cellulose fibers. Common reducing agents are fructose (fruit sugar), henna powder and used madder roots. Reducing Agent: This is the chemical that will remove excess oxygen in your vat, allowing your vat to balance and become available for dipping. This is the magic you see when the yellow-green fiber slowly changes to blue before your eyes. Oxygen in the air reconverts the weakly attached indigo and allows it to attach to the fiber, forming a stronger bond and allowing the blue color to emerge. Oxidation: Oxidation is when the indigo fiber is removed from the vat. It’s yellow-green, and scientists call this “indigo white” or “leuco indigo”. The fiber in the vat is not blue at this time. When the fiber is immersed in the vat, indigo attaches weakly to the fiber. Indigo requires that excess oxygen is removed from the vat liquid, which makes the indigo color molecule available to physically attach to fiber. The color bond between the mordanted fibers and the dyestuff is a chemical bond. Most other dyes require you to extract the dyestuff from the raw material by making a “tea” of dyestuff and liquid, or dissolving already extracted dyes in powder form with water, adding mordanted fibers and then simmering until the color has transferred to the fibers. Reduction: Indigo works differently than other natural dyes. The vat consists of room temperature or warm water and indigo stock solution. The vat can be of varying sizes but a good rule of thumb is make it large enough so that your goods can move easily in the vat liquid, and be completely covered in the solution. Vat: The vat is the actual container of indigo and ingredients where you will dip your goods. You can also create an indigo vat using the gpL method that we detail in our How To section to better control the amount of indigo and the resultant shade. Once the reaction is ready, then carefully add this stock solution to a container of water to create the vat. We have found it easier to build a vat if you mix these ingredients in a smaller container and let them react. Indigo Stock Solution (also called a Starter or Mother): Indigo is dependent on a balanced blend of indigo powder, a base or alkali such as calcium hydroxide, and a reducing agent, such as fructose or henna. The higher the gpL, the darker the vat will be. Grams per Liter (gpL): An expression used to determine the amount of indigo in a vat. An excellent resource about the history of indigo is Jenny Balfour-Paul’s book Indigo: Egyptian Mummies to Blue Jeans. Cultivation acreage plummeted and within 20 years only a fraction of the indigo used worldwide was from natural sources. The color was synthesized around 1880 by Alfred Bayer and shortly after the world indigo market collapsed as manufacturers switched to the new miracle synthetic dye. European colonizers forced Bengali and indigenous workers to grow indigo under horrible conditions, resulting in worker uprisings and revolts. Indigo was a valued historical crop and grown and tended by enslaved people in the US. Indigo was used to dye shrouds for Egyptian burials, uniforms for Napoleon’s Army, prestige cloth for African chiefs and to dye denim for blue jeans. It is the only natural plant-based blue and its colorant is present in other plants, including woad ( Isatis tinctoria), Japanese indigo, ( Persicaria tinctoria, a buckwheat) and Strobilanthes cusia, a distant cousin to the ornamental Persian Shield that you can buy at Home Depot. Indigo: Indigo is a pigment from the leaves of the indigo plant called Indigofera tinctoria, one of the oldest dyes known to humankind.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |