Sentence:  ‘<WSD>Bittiness</WSD>' occurs when dirt is incorporated into the surface from the atmosphere or dirty tools, or if the paint is not properly strained.<references/> 
Meaning of the word marked with <WSD> tags:  The inclusion of material in paint or varnish films which disturbs the smooth uniformity of the coating.<ref>1954, "Corrosion Prevention and Control", Scientific Surveys Limited, Volume 1, p. 84</ref>