Can Procion MX dyed on cotton be washed at high temperatures? Will the color stay strong?
Not only
can properly fixed Procion MX-dyed cottons be washed in hot water, they
should be washed in hot water.
The chemical bond between Procion MX dyes and the fiber, when they are applied at a high pH such as with soda ash, is so strong that the dyed fiber can be extensively boiled without breaking the bond. Not that you would normally want to boil your clothing, but if for some reason you did, it would not be a problem.
When you use Procion MX type dyes, some of the dye you apply reacts with the fiber to form this permanent bond, but some of it does not, because it may have reacted with the water instead. When the Procion MX type dye reacts with the water, we say that it is hydrolyzed; it's no good after that for use as a reactive dye. It can only react once. We need to remove this unattached excess dye. The best way to do this is to use hot water, 140°F (60°C) or above. Hot water reduces the tendency of the unattached dye to associate loosely with the fiber.
My own preferred washing-out procedure is to wash the dyed items once in cool water, either with Synthrapol detergent or with no detergent at all, to remove soda ash, salts, etc., then to wash them twice in hot water with Synthrapol or another detergent. Our washing machines here in the US usually cannot attain a water temperature higher than 140°F, but a higher temperature would be even more effective. I often do my first cold washing in the washing machine, so I don't have to bother with individually rinsing out each item. Backstaining is avoided by giving the dye reaction more time and warmth than is needed for all of the dye to react, so that there is no ready-to-react dye left on the fabric when you dump it into the washing machine.
Sometimes dye novices complain about the hydrolyzed dye washing out of the fabric. They expect all of the dye they put on the fabric to stay there, but this simply will not happen with reactive dyes. You must apply more than looks right, so that the fiber looks darker than you will want as a final result. Often my dyed items look nearly black before I wash them out.
Soemtimes you may want to dye a rayon or cotton garment whose care instructions say to wash in cold water only. You then have a choice between washing out
many times in cool water, and then taking care to wash only with similar colors in the laundry, since cool water does not wash reactive dyes out as efficiently as hot water, or of ignoring the care instructions, depending on the garment and how much risk you are willing to take. I like to buy my cotton clothing so that it will still fit after shrinking in a hot water washing, which means buying it a size larger (this may be why I almost always find Dharma's clothing to run at least one size smaller than the label says). I find that rayon clothing can survive hot water just about as well as cold, but since rayon is very fragile when wet, at
any temperature of water, it is essential to use a reliably delicate wash cycle and take extreme care not to allow the rayon to become torn or abraded. Never wash rayon in the same washload as a heavier garment, and be very careful when lifting wet rayon garments.
Paula
