Purchase the dye
Depending on how dark you want the jeans to be, buy a couple of navy blue Rit dye packets. If you are looking for a dark wash then you should not go for Rit denim blue shade. If you want your jeans to be extremely dark blue then use a black dye along with navy blue one.
Dissolve the dye in water
Mix the powder into a couple of cups of hot water and stir it hard to ensure that it has been mixed properly. Add the pre-dissolved dye solution to more hot water, preferably in a bucket or a sink. It is highly recommended that the temperature of the water should be more than 60 degrees C or 140 degrees F. Now you need to wet the jeans in extremely hot water before putting them in the sink.
Leave the jeans in the dyeing bath
Make sure that the jeans are thoroughly soaked in the hot water and leave them in the dye bath for at least an hour or until the water remains hot. The longer you allow the jeans to sit in the hot water, the better result you will get. However, while you are taking the jeans out of the water, you need to remember that denim looks darker when it is wet.
Now you should wash the jeans in warm water once before rinsing it in cold water, until it runs clear.
Clean the sink
In order to avoid any kind of stains on the sink or the bucket, you should immediately clean it using a commercial cleansing product, having removed the jeans.