Have you ever put a baseball cap in the washing machine and gotten back something that looked like it had been run over? The brim curled. The crown collapsed. The color faded in weird patches. I have ruined at least three caps this way before I figured out the right method.

Baseball caps have structured brims — usually cardboard or plastic inside — and shaped crowns. Agitation, heat, and spinning destroy both. The trick is cleaning them with as little movement as possible.

The Dishwasher Method (Seriously)

This sounds wrong. It is not. The dishwasher uses gentle water pressure and no agitation. It is perfect for caps.

1. Put the cap on the top rack. The brim should point up.
2. Use a cap cage or a plastic cap frame if you have one. If not, just make sure nothing else touches the cap.
3. Run a short, cool cycle. No heated dry. Heat warps brims.
4. Take the cap out immediately and let it air dry.

Do not use dishwasher detergent — it is too harsh for fabric. A small squirt of regular laundry detergent works fine.

Hand Wash for Sentimental Caps

If the cap is old, valuable, or irreplaceable, skip the dishwasher. Fill a sink with cool water and a teaspoon of mild detergent. Submerge the cap and gently scrub the sweatband with a soft brush. That is where almost all the dirt and oil accumulates.

Rinse with cool water. Do not wring it — squeeze gently. Place it over a bowl or ball to hold its shape while drying. A small mixing bowl works perfectly. The cap dries in that shape.

What Never to Do

Never put a baseball cap in the dryer. Ever. The heat will shrink the fabric and warp the brim. The tumbling will beat the crown out of shape. I learned this the hard way with a limited-edition cap from a brewery I liked. It came out the size of a child’s hat.

Also never use hot water. Hot water plus the cardboard brim insert equals a wavy, misshapen brim that nothing will fix. Cool water only.

Sweat Stains on the Brim

For white or light-colored caps with sweat stains, make a paste of baking soda and water. Apply it to the stained areas with an old toothbrush. Let it sit for 30 minutes, then rinse. The baking soda lifts the oils and salts that cause yellowing.