Light striped prints

Another printing fault is light pollution known as fog. This is assuming it hasn't happened in the camera.

The dark line you see running up this picture
 it the result of light
getting to the light sensitive material. Fogging .

●         It Could be where stray light from a darkroom not properly blacked out has found its way to the light sensitive side of the the paper you're using.

●         Your safe light is too close to the enlarger and or the wrong colour.

●         It can also happen if your enlarger leaks light when being used.

●         Badly stored and out of date paper can also be fogged.

The causes of these faults, also point to ways of curing them. This post suggests a way of detecting light induced fog.