Dye is see-through. When working with it, imagine working with sheets of coloured transparency film with light shining from behind.
It is this quality that leads to such vibrant results when experimenting with dyed techniques. It means that the base cloth can be seen through subsequent layers of dye. If the base is uneven, the next layer will also appear uneven.
It is very difficult to cover bleach marks. You will have to completely saturate the fibre to get rid of the mark. The lighter marks may reappear later in subsequent washes as the fabric fades again. Those particular fibres will always have less dye on them than those that were not bleached.
Bleach is very destructive, and if you did not wash it out thoroughly just after the spill happened, it is likely to damage the fibre. A fibre that has been softened in this way may not hold dye very well either. This further reduces your chances of solving the problem.
When faced with this dilemma (yes, I too am clumsy), there are only two routes that do not lead to more heartache:
If the spill is relatively small, I find a permanent black marker at my local stationer that is closest in colour and simply colour it in. Remember to keep the marker in your handbag because the ink is bound to fade and will need touching up once in awhile. (You will usually notice it on the way to a job interview or a meeting with an important investor.)
If the spill is large and the “koki-treatment” just too tacky, I simply go with the flow. I go outside to the hosepipe with the garment, the bottle of bleach, a syringe and some rubber gloves. I put on the rubber gloves, draw some bleach into the syringe and squirt it all over the garment to create an artistic dripped effect. As soon as I see the marks I want emerging, I spray the fabric off with the hosepipe to slow down the reaction.
Do not stand too close to such a project. The chlorine gas released by the reaction smells bad and can make you very ill. Try not to breathe in the fumes and wear a face mask if you have one.
I have created some fabulous “designer” garments for myself from some of my clumsier moments.
Wash the fabric thoroughly to remove all the bleach. How many washes will depend on how strong the bleach was that you used. When you can no longer smell it, you can stop washing. If you leave traces of bleach in the fabric, it will weaken the fibre and you can expect the garment to tear.
Good luck with your spill.