Why Does Cashmere Shrink After Washing?
There are small scales on cashmere fibers which form the fiber's natural outer protective layer. When the scales are subjected to hot water (above 30°C) or rubbing very hard, they open like pine cones, interlock and become tightly packed. This is basically what we call "felting" or shrinkage."
This is not a quality issue, but a natural characteristic of the fiber. What we need to do is not fight it, but adapt to it scientifically.
Four Scientific Steps to Help Cashmere Maintain Its Shape
Step 1: Water Temperature Is Key - Avoid "Hot Baths"
Be sure to tell users: forget "warm water" - use cold water instead. When hand washing, keep the water temperature below 30°C, ideally around 20°C, so that it feels slightly cool to the touch. Hot water is the number one cause of shrinkage, as it directly stimulates the fiber scales to open.
Step 2: Use the Right Detergent
Ordinary laundry powders or liquid detergents are not to be used at all since almost all of them are alkaline. Protein fiber cashmere is very similar to human hair. When you put it in an alkaline environment, the outer layer of the fiber will get broken and the clothes will become stiff and lose the natural luster.
A detergent, which is made for cashmere, is the best thing to use always. However, if you don't have one, you can consider using a gentle, neutral baby shampoo.
Step 3: The Proper Technique Is "Pressing," Not "Rubbing"
People usually make this one mistake. After a cashmere sweater is soaked, it stays pressed to prevent water going through the fibers and dirt removal. For places like the collar and cuffs, you can gently massage with your fingertips, but do not rub the garment as usual and never twist it out.
Once the washer, put the sweater on a dry towel, roll it up like a sushi, and press softly so the towel can soak up the extra water.
Step 4: Always Lay Flat to Dry
When a cashmere sweater is washed, it still contains a lot of moisture and hence, is heavier. If you hang it to dry, gravity will make the water drip down, stretching and thus, deforming the clothes and also, the shoulders will get a funny shape.
Remember, you should lay it flat on a drying rack and let it air dry naturally in a cool, ventilated place, out of direct sunlight and away from heat sources like radiators.