If your whites are going grey, it is probably because dirt removed during washing has been redeposited on the clothing as a very thin layer, the GHI says. To cure that, they advise using more detergent - the maximum dose - and washing again at the highest temperature, soaking in a bleach solution and then rinsing thoroughly.
However, it is best to avoid the problem by washing whites separately, they suggest.
Bobbling on cotton and synthetic blends is best prevented by washing garments inside out.
The GHI was set up in 1924 at a time when fewer women were going into domestic service and household appliances were beginning to become more prevalent.
But even after 92 years there is one problem they still cannot cure - jumpers that have shrunk.
"If you machine wash wool at too high a temperature or spin speed, it causes the fibres to felt and go matted, which is irreversible," Mrs Schofield said. "In less severe cases, re-wetting the item and gently stretching it can get it back to the size it should be."