Sentence:  A good formulation will keep the clothes clean and white after many washings ; whereas , with a poor formulation , the clothes exhibit a build-up of `` tattle-tale grey '' and dirty spots - <WSD>sometimes</WSD> with bad results even after the first wash . 
Meaning of the word marked with <WSD> tags:  on certain occasions or in certain cases but not always; at other times for six months"