Step 1
Make a new document, 500×1000 pixels, white background.

Step 2
Fill the selection with a black to white gradient starting from the top of image to the bottom like in the example.

Step 3
Now go on Filter/Render/Difference Cloud, then hit CTRL+F:

Step 4
It should now look like this.

Step 5
Now go to Image/Adjustments/Invert.

Step 6
Now go to Image/Adjustments/Levels Once in the level panel magnify the white zones and move the left pointer to right and the right pointer to left. Click OK.

Step 7
It should now look like this

Step 8
Now bring up the Hue/Saturation dialogue, go to Image/Adjustments/Hue/Saturation.

Step 9
Set your levels like the below image.

Step 10
Your image should now look like this.

Step 11
To end things go to Filter/Brush Strokes use the angled stroke

Step 12
Set your strokes to the following below values.

Step 13
Your completed project.