Name: Mrs O'Neill

Message: I have bought a viscose "denim coloured" two piece, and I was wondering if there is any treatment that would hold the colour, as it rubs onto undergarments, and if it is hot and sticky, onto the skin.
I would be very grateful if there was a "quick fix".

No, I'm sorry, there is no quick fix for this particular dye problem. 

The dye used in blue denim is called indigo. It can be used to dye any natural fiber, though, not only denim. Indigo is a vat dye, and like all vat dyes is applied in a very different way than other types of dye. Instead of bonding to the fiber, the dye is converted into a water-soluble form and allowed to soak into the fiber, after which it is exposed to air, which converts it to a form which is no longer soluble in water, so the particles of dye become stuck within the fiber.

When dye rubs off of indigo-dyed fabric, it is a manufacturing defect called crocking. The cause is incorrect dye application. Indigo dye should be applied by repeatedly dipping the fabric in the indigo dyebath, allowing the dye to oxidize in between dips. Sometimes the dyer skimps on effort, using fewer dips in an excessively strong dye solution, resulting in loose dye on the surface of the fabric, which easily rubs off.

There is no way to fix the loose surface dye into place when it has been misapplied in this way. Cationic dye fixatives such as Retayne are ineffective for indigo due to its lack of a negative electrical charge.

The best answer is to return the defective garment to the retailer from which you bought it, for a refund. If that is impossible, you might be able to remove enough of the loose dye from the surface of your outfit by washing it repeatedly, perhaps as many as ten times, or more, using the hottest water that the fabric can tolerate. Be very careful in handling viscose rayon when it is wet, because it lacks wet strength and is easily torn.


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