Name: SHAKATH
Message: HOW CAN WE IMPROVE WASH FASTNESS OF REACTIVE DYED YARN?

The most important thing to do is get the chemical reaction right. Fiber reactive dyes are extremely washfast, compared to most dyes, because they form a permanent chemical bind to the fiber.

First, you must have the right kind of fiber for the reactive dyes to reactive with. Forget about synthetics such as acrylic, acetate, or polyester. They do not react with fiber reactive dye. They do not have the right chemistry. In contrast, cotton, linen, and rayon yarns react very well with the fiber reactive dyes that are designed for cellulose, such as Procion MX, Cibacron F, or Drimarene K dyes. Wool, and other animal fibers such as angora and mohair, as well as nylon, react well with the reactives found in the Lanaset range of dyes. (The Lanaset dyes include both reactive and 1:2 premetalized acid dyes.) Silk, which is uniquely dyeable, works well with both.

Next, you must have the right pH for the reaction. The cellulose fiber reactive dyes prefer a high pH, around 10.5 to 11. Soda ash, also known by its chemical name, sodium carbonate, as well as the old name washing soda, is ideal for reaching this pH range. Try pH paper in your dyebath, before actually adding the dye, or in a mock dye reaction from which you have omitted the dye but used exactly your usual quantities of other items, to make sure that your pH is appropriate. The Lanaset fiber reactives used on wool, in contrast, require an acidic, low pH, as is usual for wool dyes. Cotton cannot be dyed at a low pH, but wool disintegrates at a high pH! In addition, Procion MX, Cibacron F, and Drimarene K dyes can also be used on animal fibers, such as wool, at a low pH.

Third, you must have a high enough reaction temperature. Some fiber reactive dyes, such as Procion H (not the same at all as Procion MX!), must be steamed for the reaction with the fiber to take place. Procion MX, Cibacron F, or Drimarene K require a temperature range which is called "cold" by the textile industry, but is not at all cold to anyone outside of that industry. The minimum temperature for dye reactions that will be left to react for twenty-four hours is 70 degrees Fahrenheit (21 C), but higher temperatures may lead to better dye yields, and take less time. I prefer temperatures of 85 to 95 degrees F. (30 to 35 degrees C.), myself.

Fourth of course is the reaction time, which must be chosen to work well with the reaction temperature. Lower temperatures, near the minimum, require much more time than higher temperatures.

Then there are factors which are not truly involved in the washfastness of the reacted dye, but which have an effect on the brightness of the results. The yarn or fabric must be free of any coatings which will prevent the dye from reaching the cellulose (or protein) molecules, such as permanent press or stain-resistant finishes. For less permanent finishes, such as sizing, the fiber must be scoured before use. Prewashing is sufficient for PFD items (marketed as being "Prepared For Dyeing"), but other fiber may have to be boiled with soda ash and detergent before dyeing. See the instructions for pre-scouring on Pro Chemical & Dye's website.

Fiber that has been treated with starch before sale can be extraordinarily difficult to get clean of starch. Starch dyes well with reactive dyes, but then gradually bleeds out in the laundry. Even boiling does not always remove the starch. To determine whether your fiber is contaminated with starch, put a drop of iodine on it. If it turns blue, you know that this is your problem. Try to find a source which does not sell you goods with starch in them.

If you like to heat set your reactions - many people find it convenient to microwave their Procion MX reactions for speed and brightness, and of course steaming is the original form of heat-setting - you may find better results with the use of Ludigol, which helps prevent the reduction of dyes at high temperatures. It is not needed at room temperature, however.

After you have dyed your yarn with careful attention to ALL of the above factors, you will find yourself with excess unattached dye that must be removed. If you do your first rinsing in hot water, you may find that this dye becomes a little more firmly associated with the fiber, and reluctant to leave, so that it comes out gradually over many washings. This is very undesirable. You need to remove all of the unreacted dye. To do so, make sure that your first rinsing is in cool water, 90 degrees F. (32 C) or below. Then, all following washings should be as hot as the fiber will allow. Often two complete wash cycles in hot water is sufficient. In order to determine whether your washing has been sufficient, press the dyed yarn between two white cotton cloths with a hot iron. If any dye transfers to the white cloth, there is more unattached dye that must be washed out. A shortcut is to soak the dyed fiber in hot water for a while before washing again. The hotter the water is, the more effectively it will remove dye. For home use, increasing the temperature of the water heater may help. Washing machines that can heat the water to a much higher temperature are very convenient at this stage, but they are difficult to get and very expensive in North America, though they are readily available in Europe.

If you are unable to do as much washing out of unattached dye as is needed, such as in the case of being located in the desert or while experiencing a drought, you can substitute an ionic dye fixative for some of the washing. This is a commercial product that essentially glues the excess unattached dye inside the fiber, and is added only after all dyeing steps have been completed. This dye fixative is essential for use in dyeing with direct dyes, which are not very washfast, but can also be used, instead of proper technique, by those using fiber reactive dye. The form most commonly available at retail is called by the brand name Retayne, which many dye retailers sell; there are also other brands available. Ask your dye supplier about this.