To test the colourfastness of a garment, dampen a small area of hem or inside seam, then iron a piece of white fabric or kitchen paper onto it. If any colour blots off, then the garment is not colourfast. It should be washed separately in cold water and rinse it immediately. Non colourfast garments should not be left to soak.
Hand washing detergents should be used for home laundry when cleaning fine fabrics.. Properties to look for when using hand-washing detergents include use in cold water, quick dissolving in cold water, and complete rinsing of the detergent after the wash.
To test hand washing detergents or any detergent, dissolve recommended amount of detergent in cold water. Allow the detergent and water to sit for 24 hours. Note the residue, if any, in the bottom - this residue may be difficult to rinse out of your garment