Delicate fibres such as white lace can become worn and dingy over time. White lace tends to accumulate yellow stains on it, but a common mistake that many people make with lace is to bleach it or submerse it in harsh chemicals. Lace is delicate, and, as such, must be treated delicately. If you want to attempt to remove yellow stains from white lace, the safest method is to use a gentle washing powder along with warm water.
Pour a drop of the washing powder from the cup directly onto the yellow stains on the white lace. The drop should be approximately the size of a 50p piece. If the yellow stains are larger, add more drops as needed. Pour the remainder of the washing powder from the cup into the wash basin.
Rub the washing powder very gently into the white lace. Add warm water to the wash basin, along with 1/2 cup of borax. Put the white lace into the wash basin, and allow it to soak for approximately 30 minutes.
Rub the white lace against itself to wash it, then rinse the lace with cold water until the water runs clear. Check to see if the yellow stains are gone. If they are not, repeat the process.
Pour 1/2 cup of washing powder into the wash basin, and this time fill the basin with cold water. Place the white lace in the water and let it soak for 30 minutes again. When the 30 minutes are up, gently wring the excess water from the white lace, rinse in cool water, and hang it up to air dry.
Find borax in the washing powder aisles of supermarkets or chemist shops.
If the yellow stains have not come out of the white lace by the second attempt, then the stains are likely permanent. Some yellows stains cannot be completely removed because the moisture and contaminants that make the lace yellow could have weakened the fibres as well.
Avoid using bleach or any other harsh chemicals on delicate fabrics like lace because you don't want the fabrics to become so brittle that they rip or break.