Synthetic dress slacks can develop shiny patches after extensive wear and improper ironing techniques, but in some cases, you may be able to reverse the shine. Noticeable patches of sheen make your pants look cheap, regardless of their initial cost. If the cause of shine is simple wear, you will see sheen across the backside from sitting. You may have to replace pants that appear faded or worn. Prolong the life of your polyester pants by laundering them inside-out. Press the inside-out pants on a low heat setting to remove wrinkles without causing more shine.

Locate the shiny areas on your pants. Dampen a clean, dry washcloth with 3 percent hydrogen peroxide.

Rub the shiny area with the peroxide lightly to lift the nap. If you have a dark pair of pants, test the peroxide on a hem before exposing the pants to the peroxide. Some fabrics are not color-safe and may fade when rubbed with peroxide.

Turn the pants inside-out and wash them according to the directions on the label. Remove damp pants from the washer promptly and dry them on a low heat.

Place the dry pants on an ironing board. Leave the pants inside-out, but straighten them and smooth the fabric with your hands while the iron heats. Put the iron on a low- to medium-heat setting. If your iron has a fabric selection, choose polyester.

Cover the pants with a piece of flannel fabric. You will use the flannel as a heat barrier between the iron and the pants. This will diminish the chance for sheen due to high iron temperatures.

Press the pants with the iron lightly. Do not rub the iron down the length of the fabric. The tap-and-press method works best to avoid shine. You can also use the "kissing the fabric" method on your polyester pants. Remove the flannel and hold the iron just above the pants. This exposes the pants to the iron's heat without exposing your pants to direct heat.