Why Some Pants Say Dry Clean Only

Dry-clean-only pants have a reputation for fussiness. It's partly deserved. But the label isn't usually there to sell you dry cleaning. It's there because something in the garment reacts badly to water, heat or agitation, and the manufacturer would rather you didn't find out which.

What dry cleaning actually is

Dry cleaning is not dry. Clothes are cleaned in a machine, with a liquid, and tumbled. The difference is that the liquid is a solvent instead of water. The most common solvent in the U.S. has long been perchloroethylene, with hydrocarbon, silicone-based and liquid carbon dioxide systems as alternatives. Many cleaners also offer professional wet cleaning, which uses water with computer-controlled machines, specialized detergents and tension-finishing equipment that holds the garment's shape as it dries.

Solvents dissolve oils and grease well, and they don't make fibers swell the way water does. That second part is the important one.

Fabrics that don't like water

Wool

Wool fibers are covered in tiny overlapping scales. Add warm water and agitation and those scales lock together. This is felting, and it's permanent. A pair of wool trousers can come out of a hot wash noticeably smaller, thicker and stiffer. Some wool is treated to resist this and labeled machine washable. Most tailored wool trousers aren't.

Rayon and viscose

Rayon is made from wood pulp and loses a large share of its strength when wet. It can shrink, stretch out of shape or tear more easily in the wash, and some rayon changes texture after one wash in a way that doesn't reverse.

Silk

Silk can water-spot, lose its sheen and bleed dye. Some silk is washable by hand. A lot of silk trousers use dyes and finishes that aren't.

Acetate

Often used in linings. Acetate is sensitive to heat and wrinkles permanently if it's handled hot and wet.

Construction that doesn't like water

Sometimes the fabric is fine and the problem is how the pants are built.

• Linings. If the shell and the lining are different fibers, they can shrink at different rates. The pants pucker and hang wrong.
• Interfacing. The stiff layers inside waistbands and fly fronts are sometimes fused with adhesive that softens or bubbles in hot water.
• Pleats and creases. Sharp pleats are often heat-set. Washing can soften them.
• Trims. Beading, sequins, leather patches and some buttons don't survive a washing machine, or damage everything else in it.

So can you ever ignore the label?

People do, sometimes successfully. A polyester dress pant labeled "dry clean" may wash fine on a delicate cycle. But you're taking on the risk yourself, and the downside with wool, rayon and lined tailoring is that the damage is permanent. If the trousers matter to you, the label is cheaper than replacement.

Making dry-clean-only pants last

• Clean them less. Dry cleaning is gentle but not nothing. Brush wool trousers after wearing and hang them to air out. They'll need cleaning less often than you think.
• Deal with spills immediately. Blot, don't rub, and don't add water to a stain on a dry-clean-only fabric unless you know it's safe.
• Hang them properly. Clamp hangers at the hem or cuff, or fold over a wide bar hanger along the crease.
• Tell the cleaner what the stain is. Knowing it's oil versus wine changes the treatment.

How I handle them

Dry-clean-only pants are Special Pants. They go to professional cleaning using the process the label specifies, and they're pressed where they should be. It costs more than washing jeans, because it is more than washing jeans. Pricing is here.

Some pants go in a washing machine. Some pants apparently require chemistry. I'll deal with both.