Removal of magnetism from a paramagnetic substance. It is principally used for watches which have become magnetized by exposure to the magnetic field surrounding dynamos or motors.

The general principles of most methods are to rotate the object, as a watch, in a strong field, and while it is rotating to gradually remove it from the field, or to gradually reduce the intensity of the field itself to zero. A conical coil of wire within which the field is produced in which the watch is placed is sometimes used, the idea being that the field within such a coil is strongest at its base. Such a coil supplied by an alternating current is found effectual (J. J. Wright).

If a magnetized watch is made to turn rapidly at the end of a twisted string and is gradually brought near to and withdrawn from the poles of a powerful dynamo it may be considerably improved.

A hollow coil of wire connected with a pole changer and dip-battery has been used. The battery creates a strong field within the coil. The watch is placed there and the pole changer is worked so as to reverse the polarity of the field very frequently. By the same action of the pole changer the plates of the battery are gradually withdrawn from the solution so as to gradually reduce the magnetic field to zero while constantly reversing its polarity. (G. M. Hopkins.)

Steel may be demagnetized by jarring when held out of the magnetic meridian, or by heating to redness.