That favourite pair of jeans -- the pair that fits perfectly and only seems to get more comfortable the older it gets -- those are the jeans you happened to be wearing when a bit of bleach leapt from its container and marred its otherwise perfect appearance. Spot-dyeing your jeans will likely cover the spots, but the natural fading process of the dye may cause them to reappear. Matching the current dye of your jeans can also make spot-dyeing less desirable. To truly eradicate the white marks you will need to redye your jeans.
Wash your jeans and do not use any fabric softeners. Shake out excess water or spin them again in the washing machine to remove excess water. Do not put them in the dryer.
Spread a bin bag, or other flat plastic sheeting, over your work area to protect it from the dye. Lay your jeans down so you have access to the bleach spots. Place cardboard or a plastic barrier inside your jeans where you will be applying the dye so the dye does not leak through to the other side of your jeans.
Put your gloves on. Mix the dye according to the manufacturer's directions. For spot-dyeing, liquid dye is easier to handle than powdered dye. If you're using RIT brand fabric dye, you can mix 2 tbsp of dye with 118 ml (1/2 cup) hot water.
Apply a bit of dye to your cloth, pinching out any extra. If the spots are small, use a cotton swab. Rub the white mark with the dye-soaked cloth or swab. The area that is dyed should be the same colour as your jeans.
Wait for 20 minutes to let the dye set. Cover your ironing board with an old towel and steam press the marks, with your iron on the cotton setting (or the hot setting).
Wash your jeans in a cold water cycle with a delicate detergent. Dry as usual.
Re-dye the jeans
Wash your jeans as usual, omitting the use of fabric softeners. Put on your gloves and use clothing colour remover to the manufacturer's specifications. Most colour removers require you to mix the colour remover with hot water, add the garment and soak it, agitating the mixture from time to time.
Rinse your jeans. Wash them as indicated by the manufacturer of the colour remover.
Mix the dye according to its instructions. For liquid dye, the general procedure is to mix about 113 g (4 oz) of dye to 13.5 litres (3 gallons) of very hot water. Powder dyes are generally mixed using 1 package to 13.5 litres (3 gallons) of water and 273 g (1 cup) of salt. Use your plastic mixing spoon to stir the dye until it is evenly disbursed in the liquid.
Add your jeans. Stir the jeans every 5 to 10 minutes to achieve an even colour. Let them soak for up to one hour. The longer your jeans stay in the dye, the darker they will be.
Rinse the jeans in warm water, slowly decreasing the water temperature until the water is cold and runs clear.
Wash the jeans in cold water with detergent. Run them through an extra cold water rinse cycle to make sure all the excess dye is removed. Dry them as usual.
Dye and colour remover are most commonly found in craft shops or supermarkets, though you are likely to find a better selection of colours at a craft shop. RIT is a commonly found brand in the UK. Mix different dyes to best match the colour of your jeans. Clean up any dye immediately to prevent staining counters, sinks or floors. Wear old clothes that you won't mind ruining in case you splatter dye on yourself.
Do not deeply inhale dye or colour remover or get them on your skin. If you do inhale these products, remove yourself from your workstation and seek medical attention. If products get on your skin or eyes, rinse with clean water for at least 15 minutes. If irritation persists, seek medical attention.