The permanent setting of synthetic fibers in creases pleats or shapes should never be attempted domestically or without the correct equipment. Efficient heat setting requires much more precise control of temperature and time than is possible with ordinary pressing equipment. Special presses are used which can be accurately controlled at temperature from 150* to 200*c together with timing devices which open the press. Theoretically synthetic fibers can be set at 100*c but higher temperatures give a more durable effect bur need strict time control to prevent damage. If permanent setting is attempted without this equipment it will not be sufficiently durable, even if it is achieved at all. When synthetic fibers are being pressed ordinary care must be taken to avoid pressing in unwanted creases because these may be very difficult to remove completely.