Name: Juliet
Message: What colorfastness test closely relates to body staining? If I have very low colorfastness rating, does it mean the colorant will most likely to adhere on the skin of wearer? 

Yes, but even relatively poorly washfast dyes, when properly applied, should not stain the skin of the wearer. When dye transfers from the clothing to the wearer, the problem is usually that the dye was either applied wrong, or excess dye was not washed out afterwards as it should have been. Dyes that are so poorly washfast as to commonly rub off are not often recommended for use on clothing. Even the worst dyes we see in our lists of colorfastness are better than many dyes we've never heard of.

Crocking is what it is called when dry dye rubs off onto things or people. Dye that crocks is usually loosely adhering to the outside of the fiber, instead of being properly attached to the fiber molecules themselves.

Crocking is a common fault for improperly applied vat dyes such as indigo, especially when it is dyed by novices that have not yet mastered the technique. Indigo is soluble when in the dye vat, and can then penetrate the fiber, but becomes insoluble immediately upon exposure to air. The way to properly dye a deep indigo is not to prepare an extra-strong indigo bath, but instead to use a fairly weak dyebath and dip the fiber repeatedly. It is not unusual to dip a single length of fabric or yarn into the indigo dyebath twenty times, for a lovely intense color that does not rub off.

Crocking is also seen when a novice dyer applies all-purpose dye or fiber reactive dye, but skips the essential step of washing out unattached dyes afterwards. Dye must never be used in any application in which thorough washing afterwards is not possible. An example would be painting Rit dye onto a couch and letting it dry. The excess dye will rub off and ruin the clothing of people who sit upon it. Fiber reactive dyes, such as Procion MX dye, must be washed several times, preferably in the hottest of water, in order to remove the excess unattached dye, leaving behind on the fabric only the strongly-bonded molecules of permanent dye.

When a poorly washfast dye, such as Rit all-purpose dye, is used on clothing, washing excess dye out afterwards should prevent crocking. However, washfastness will remain poor even after this essential washing step, if the dye is from a poorly washfast group of dyes, such as all-purpose dye or direct dye. The only solution to this problem, other than starting with a superior dye to begin with, instead, is to apply a commercial dye fixative, such as Retayne. These cationic dye fixatives are attracted to the dye molecule and help to stick it in place in the fiber. Unfortunately, they work only on dyes which have a negative charge, which means that they cannot be expected to help with vat dyes such as indigo, nor with a class of dyes called basic dyes which is rarely used at home. Cationic dye fixatives cannot be purchased from most crafts stores, except for some very good quilting supply stores, and usually must be mail-ordered from a good dye supplier such as the ones listed on my page of Sources for Dyeing Supplies Around the World.

Crocking dye on clothing or furniture is considered a manufacturing defect and should be returned to the seller.

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