4. Setting the Floss Colour

Floss is generally colourfast, but some people like to be very cautious when using dark or intense colours in heirloom quality projects. If you choose to be this cautious, do the following.

• Remove the floss from the paper wrapper.
• Place each skein of floss in a separate glass container containing cool or room temperature distilled water. Some people recommend adding vinegar or salt to the water, but the usefulness of the vinegar or salt varies with the type of dye and may even cause damage.
• Rinse the floss in the distilled water.
• If the water does not remain clear, replace the water and rinse again.
• Repeat until the water stays clear.
• Place the wet floss on a white paper towel to dry. The floss colour should not bleed onto the white towel. If it does, rinse the floss again.

Obviously, you should not do this if you know the floss was dyed with a non-colourfast dye.

source : www.mismatch.co.uk