# How to Wash a Cap Without Losing Its Shape > Can you wash a cap in the dishwasher? No, that is a myth. Hand wash or machine wash (mesh bag, 30 °C), dry on a form. Method by fabric. **Published :** 2026-03-16 · **Updated :** 2026-04-25 --- **Résumé :** **In short:** most modern caps (cotton, polyester, plastic brim) can be washed **by hand** in a basin of warm water at 30 °C or **in the machine** inside a mesh bag (delicate cycle). The key: **dry on a form** (bowl, ball) to maintain the crown shape. Never tumble dry. And no, the dishwasher is not a good idea. ## At a glance - **Check the brim** — plastic (modern) = washable. Cardboard (vintage) = no water. - **30 °C maximum** — hand wash in a basin or machine wash in a mesh bag. - **Dry on a form** — bowl, ball, round box. Never tumble dry. - **Dishwasher = no** — water too hot, detergent too harsh, drying destructive. ## Which cap gets washed how? | Fabric | Brim | Washing | Drying | |---|---|---|---| | Cotton (classic baseball) | Plastic | Hand or machine 30 °C delicate | On a form, air dry | | Polyester (sport, running) | Plastic | Hand or machine 30 °C | On a form, air dry (dries fast) | | Wool / felt | Varies | Hand wash only, cold water | Flat on towel with form | | Leather / faux leather | Rigid | Damp cloth only | Air dry | | Vintage cap (pre-2000) | Cardboard | Surface only (cloth) | Air dry, do not wet the brim | ## By fabric: the right protocol Each fabric reacts differently to water, heat, and agitation. Here is the precise protocol by cap type. ### Cotton cap (classic baseball) Cotton is the most common material and the easiest to care for. It handles water and soap well, but it **shrinks with heat** (above 40 °C) and **bleeds** if the dyes are not fixed. - **Washing**: hand wash (30 °C basin + [Marseille soap](https://amzn.to/48721mK)) or machine (mesh bag, 30 °C delicate). - **Detergent**: mild, no bleach. [Baking soda](/en/blog/baking-soda-laundry/index.md) works well for pre-treating sweat stains. - **Drying**: on a form (inverted bowl), never tumble dry. Cotton dries in 12-24 hours in the air. - **Precaution**: dark caps (black, navy) may bleed on the first wash. Wash them alone the first time. ### Polyester cap (sport, running) Polyester is durable, dries fast, and does not warp. It is the most forgiving fabric, ideal for frequently worn sport caps. - **Washing**: machine 30 °C synthetic cycle, mesh bag. Handles normal spin (600-800 rpm). - **Detergent**: no fabric softener. Like [sportswear](/en/blog/sportswear-care-guide/index.md), softener clogs polyester micropores and traps odors. - **Drying**: on a form or simply placed on a surface — polyester regains its shape naturally. Dries in 2-4 hours. - **Frequency**: after every outing in summer (sweat), every 2-3 outings in winter. ### Wool or felt cap Wool is delicate: it **felts** (shrinks and stiffens) in contact with hot water or friction. Felt is even more sensitive. - **Washing**: hand wash only, cold water (20 °C max), wool-specific detergent or gentle shampoo. - **Technique**: do not rub. Blot dirty areas with a damp cloth. If you must submerge, do so briefly without agitation. - **Rinsing**: cold water, without wringing. Press gently between two dry towels. - **Drying**: flat on a towel, shape maintained by a bowl. Keep away from direct heat. Allow 24-48 hours. ### Cap with leather or faux leather brim Leather (or faux) cannot handle immersion. Water softens it, warps it, and causes cracking as it dries. - **Crown cleaning**: if the crown is fabric, clean with a damp cloth + mild soap, carefully avoiding the brim. - **Brim cleaning**: wipe with a slightly damp cloth. For stains, use leather soap. Dry immediately. - **Maintenance**: apply a leather moisturizer or balm twice a year to prevent cracking. ## Structured vs. unstructured caps The distinction between **structured** and **unstructured** caps matters for washing. ### Structured cap (fitted, rigid snapback) Structured caps have a **rigid reinforcement** in the front panels that maintains the domed shape. This reinforcement is now **thermofused plastic** (plastic buckram) on virtually all models since the 2000s. - **Machine**: possible in a mesh bag, delicate cycle 30 °C, gentle spin. The plastic reinforcement holds up well. - **Drying**: essential to dry on a form (bowl) to maintain the front panel curve during drying. ### Unstructured cap (dad cap, 5-panel soft) Unstructured caps have no rigid reinforcement — the crown is soft and conforms to the head shape. They are easier to wash because there is no structure to preserve. - **Machine**: in a mesh bag, 30 °C delicate. The cap naturally returns to shape on the head. - **Drying**: on a form or flat — the crown's softness is an advantage. ### The case of cardboard-brim caps (pre-2000) > **Warning:** > - **Vintage caps (before approx. 2000) often have a cardboard brim.** Cardboard softens on contact with water, buckles, and never regains its shape. If you have a vintage cap you value, NEVER submerge it. Clean only the surface with a slightly damp cloth. **How to tell cardboard from plastic**: gently bend the brim. If it folds easily and does not spring back, it is cardboard. If it is rigid and springs back, it is plastic. ## Method 1: hand washing (recommended) This is the safest method — it best preserves the shape. - **Fill a basin** — warm water (30 °C) + a small dose of mild detergent or Marseille soap. - **Pre-treat the headband** — scrub sweat stains with a soft toothbrush + baking soda or soap. - **Soak and scrub** — submerge the cap, gently scrub dirty areas with fingers or a soft brush. - **Rinse 2-3 times** — clear water until all suds are gone. Detergent residue dries as white marks. - **Blot without wringing** — press gently between two towels to absorb excess water. ### Detailed hand wash: step by step Hand washing is the safest method for all caps. Here is the detailed protocol. **Supplies needed**: a basin or clean sink, [Marseille soap](https://amzn.to/48721mK) (or a mild detergent), a soft toothbrush (used), two clean towels, a bowl for drying. 1. **Prepare the bath**: fill a basin with warm water (30 °C — the temperature of a comfortable shower). Add a dab of Marseille soap or a teaspoon of mild detergent. Mix to dissolve. 2. **Pre-treat the headband**: the inner headband (sweatband) concentrates sweat and sebum. Wet it, apply Marseille soap directly, and scrub gently with the toothbrush. Focus on yellowed areas. Leave for 15-20 minutes. 3. **Submerge and scrub**: dip the cap into the basin. With your fingers or the soft brush, gently scrub dirty areas (crown, brim edge, forehead contact areas). Do not scrub the brim itself — simply wipe it with a cloth. 4. **Rinse thoroughly**: empty the basin and rinse the cap under clear water, 2 to 3 times minimum. Soap residue dries as white marks on dark fabrics — it must be fully eliminated. 5. **Blot without wringing**: place the cap on a towel, fold the towel over, and press gently. Never wring the cap — you would deform the structure. ### By stain type on the headband The **inner headband** (sweatband) is the dirtiest area. It accumulates sweat, forehead sebum, and sometimes makeup. Each stain type needs different pre-treatment: - **Sweat / salt rings** (white marks): baking soda paste (3 parts baking soda + 1 part water), scrub with a toothbrush, leave 20-30 min. Baking soda neutralizes uric acid in sweat. - **Foundation / sunscreen**: a drop of dish soap on the area, scrub gently. Dish soap emulsifies the fatty compounds in makeup. - **Dirt / mud**: let dry completely, then brush off the maximum dry. Wash normally afterward. - **Old yellowed sweat**: 1-hour soak in a mix of warm water + white vinegar (50/50) before washing. For stubborn cases, see our yellow stain guide. ## Method 2: machine washing Possible for cotton and polyester caps with a plastic brim. - 🧺 **Mesh bag required** — Place the cap in a laundry bag to protect the shape and prevent straps from snagging in the drum. - 🌡️ **30 °C delicate** — Delicate or wool cycle. Gentle spin (400-600 rpm max). No quick or intensive cycle. - 🧴 **Mild detergent** — Reduced dose. Avoid bleach and harsh detergents that fade the fabric and brim edge. ### Sport / running caps: special case Running and trail caps made of **technical polyester** are designed for frequent washing (heavy sweating). They are more forgiving than cotton caps: - **Machine**: 30 °C synthetic cycle, in a laundry bag. Normal spin (600-800 rpm) — polyester does not warp. - **No fabric softener**: like [sportswear](/en/blog/sportswear-care-guide/index.md), softener clogs micropores and traps odors. - **Frequency**: after every outing in summer, every 2-3 outings in winter. Polyester dries in 2-3 hours. - **Drying**: on a form or simply on a convex object — polyester regains its shape naturally. ## Drying: the shape is everything > Place the cap on an **inverted bowl** whose diameter matches the > crown size (approx. 18-20 cm for an adult). The bowl maintains the crown shape > while the brim dries flat. Alternatives by practicality: > > > > > > • **Inflated balloon** — adjustable diameter, perfectly > conforms to the shape > > > > • **Glass jar** (Mason jar type) — stable, good diameter > > > > • **Tissue box** — free and available in every home > > > > • **Dedicated cap dryer** (Cap Washer / cap cage) — available > online, approx. $5-10 > > > > > > Full drying in 12-24 hours in the air. Never place near a radiator — direct > heat can warp the plastic brim and shrink cotton. ### Why the tumble dryer is off-limits Tumble dryer heat (60-80 °C) and drum agitation are destructive for caps: - **Shrinkage**: cotton contracts under heat, and the cap becomes too small. - **Deformation**: the crown and brim are tossed around the drum, losing their shape. - **Fading**: intense heat accelerates color loss, especially on cheap dyes. - **Plastic brim**: above 70 °C, the brim plastic can soften and warp irreversibly. Air drying on a form is the only method that fully preserves the cap's structure. It takes longer (12-24 hours), but it is risk-free. For more on textile-appropriate drying, check our complete drying guide. ## The dishwasher myth > The advice to wash caps in the dishwasher has circulated online for years. In > practice: > > > > > > • Water reaches **60-70 °C** — too hot for most caps (fading, > cotton shrinkage). > > > > • **Dishwasher detergents** are highly alkaline and abrasive > — formulated for food grease, not textiles. > > > > • **Heat drying** warps the brim and crown. > > > > • Your cap comes out clean but > **faded, stiff, and potentially misshapen**. A 30 °C basin with > soap gives a better result in 15 minutes. ## Mistakes to avoid > **Warning:** > - **Tumble drying** — heat and agitation deform the crown and brim, often irreversibly. > - **Wringing to dry** — you deform the structure. Press between two towels. > - **Washing a cardboard-brim cap** — cardboard softens, buckles, and never recovers. Surface clean only. > - **Using bleach** — fades the fabric and weakens stitching. Even on white, sodium percarbonate is safer. > - **Drying flat without a form** — the crown flattens and the cap loses its structure. **Produit recommandé** *Cet article contient des liens affiliés. Les prix et la disponibilité peuvent varier.* ## Sources and references - New Era, Cap care FAQ, consulted March 16, 2026 - 47 Brand, *How to wash your cap*, consulted March 23, 2026 - [Sweat stains: removing yellow marks](/en/blog/sweat-stains-yellow-marks/index.md) - [Baking soda and laundry](/en/blog/baking-soda-laundry/index.md) - [Laundry care label symbols guide](/en/blog/laundry-care-labels/index.md) - [Washing temperature guide](/en/blog/washing-temperatures/index.md) - [Sportswear care guide](/en/blog/sportswear-care-guide/index.md) - [Complete drying guide](/en/blog/tumble-dryer-guide/index.md) - [Preventing laundry shrinkage](/en/blog/prevent-shrinking-guide/index.md)