Sweaters are an essential item in any wardrobe, but they are not recommended to be washed often. The reason for this is that washing can affect the warmth of the sweater. The warmth of clothing comes from insulation, and the air is a poor conductor of heat.

The fluffier the clothing, the more air can be stored, and the warmer it will be. When clothes are washed, water immersion can destroy some of the pores, which can make the clothes dense and less warm.

The fabric composition of the sweater can generally be seen on the inside of its washing label. Regular sweater products will indicate their various components, which are generally made of cotton or chemical fiber fabrics. Cotton fabrics, such as the common hand-knitted sweater, are generally made of cotton thread woven.

More retro hand-knitted sweaters are generally made of purchased cotton wool that is hand-knitted. However, cotton thread is generally thicker, and knitted sweaters are more prone to shrink after a few washes, which is one of the reasons why people rarely knit sweaters themselves.

Chemical fiber fabrics, such as acrylic and spandex, occupy most of the market for knitted sweaters. A casual search online for knitted sweaters will mostly show acrylic, spandex, and polyester components.

These fabrics are low-cost and can be mass-produced, which makes them popular among young people who don't pursue quality. Polyester and other synthetic chemical fiber fabrics are also commonly used in knitted sweaters on the market.

If you want to wash your sweater, there are a few things to keep in mind. First, hang the sweater outdoors and use a stick to pump it inside and out to remove dust. Repeat this process several times until the dust is mostly removed.

Then, soak the sweater in warm water and gently squeeze it with both hands for a while. Take it out and clasp the water dry, then soak the sweater in laundry detergent at 40 to 50 degrees Celsius. Rinse off the detergent with warm water.

After soaking for half an hour, keep squeezing the sweater with your hands, the technique is like kneading with both hands. Be sure to avoid wringing, not to mention rubbing with a scrub board. After washing, rinse the sweater in warm water several times.

For the first rinse, you can add some vinegar to the water to make the sweater fluffy and shiny. If the water is not clean, it can affect the fluffiness of the sweater.

The washed sweater should be put in a net to shake off the water as much as possible, do not wring it out, and do not dry it directly on the sweater rack with water to avoid deformation of the sweater and reduce the elasticity.

You should dry the sweater in a ventilated and dry place, and keep turning it over. When the sweater is 80% dry, you can take it out of the pocket to dry.

In conclusion, sweaters are not recommended to be washed often because they can affect the warmth of the sweater. The fabric composition of the sweater can generally be seen on the inside of its washing label.

Cotton and chemical fiber fabrics are commonly used in sweaters. If you need to wash your sweater, it's important to do so gently and in a way that preserves the warmth and fluffiness of the sweater.