Color dodge not working

Yesterday I brought up an image and started to use the color dodge effect with brushes. When I finished, I saved my picture and went to bed. When I woke up the next morning, I added a black area to the image. When I tried using the color dodge with the brushes, it didn't work. So, just to see if it was just screwing with me, I went over the the portion of the image I was working on yesterday and it worked. So I brought out a new image, just plain black, and it didn't work. Does anyone know what's the problem or what I should do?

does black just disapear when you dodge it?

Don't worry 'bout it, I figured it out ;)

so what was the problem

This is pretty simple....

Color dodge has no effect on pure black... Dont ask me why but it is this way... But here the trick, use a really dark tone of gray (like 95 %) then use dodge, once your done done just darken it a little bit... Ass son as the color is not 100% black it work!

In the same manner Color buen will not work on pure white...