Does X ray make a radiograph black or white ?

If you happened to see an X-ray radiograph of the human body (e.g. the chest), you would observe that the ribs appear white on the radiograph, whereas the lungs appear black.
Bones inside human body are of higher density than other body tissues. X-rays will be absorbed more by high density objects. This causes the X-rays reaching the film less intense after passing through the bones than those passing through soft tissues. The more exposure of the radiograph, the darker it will be observed and vice versa. The difference in intensity of the X-rays will cause different degree of exposure of the radiograph, with the the less intense X-rays (due to more absorption by the bones) causing the radiogrpah less exposed and appearing white.