Test sieves are analytical instruments and should be carefully treated as such before, during and after sieving.
Is my sieve still good?
A detailed look at appropriate care and maintenance of woven mesh analytical test sieves
We recommend that, before new sieves are used for the first time, they are rinsed with ethanol or isopropanol to remove any preservative residues. When not in use they should be stored in a dry, dust-free location.
During the sieving process no attempt should be made to force the sample through the wire gauze. Even gently brushing the sample, particularly with fine mesh gauzes, or the use of improper mechanical sieving aids (such as metal balls, cubes, chains, etc.) could result in alterations to the gauze or even damage to the sieve body.
A detailed look into the appropriate care, use and maintenance in explained in the linked article.