I n this tutorial you will learn how to make cracks in surfaces. Start with a texture or a text. (fig.1) Then make a new layer over it. [Shift+Ctrl+N] Select a black foreground color and paint the cracks with the "Airbrush Tool" [J] or "Paintbrush Tool".

When you have painted the cracks, invert the color of them. [Ctrl+I]. This will let you off with the cracks white. (fig.2) Now, duplicate the layer with the cracks on once (Layer | Duplicate Layer). Then invert the layer on the top.

When you have painted the cracks, invert the color of them. [Ctrl+I]. This will let you off with the cracks white. (fig.2) Now, duplicate the layer with the cracks on once (Layer | Duplicate Layer). Then invert the layer on the top. Move the black layer with cracks one step up and one to the right (To do this, select the "Move Tool" and with your keyboard , press the up-arrow once and the right-arrow once.). Now you can see the cracks. You're not done yet. Set the blending mode of the black cracks to "Soft Light" (fig.3), and duplicate it one or two times more.

Now you should see the crack-effect clearly. Your cracks should look like fig.4 if you followed the tutorial. And as usual, add some effects to make it cool :)
Your final image could be like fig.5