The veil is made out of crape, which is traditionally associated with the ritual of mourning. The colour of the veil, black, increases the funereal sense that hangs about Mr Hooper. His general demeanour is entirely in keeping with such gloomy associations. He is quite a kindly man, but he always appears sorrowful:
There was the black veil, swathed round Mr Hooper's forehead, and concealing every feature above his placid mouth, on which, at times, they could perceive the glimmerings of a melancholy smile.
Mr Hooper, then, is always calm, or 'placid', but also 'melancholy'. The veil which he never takes off accentuates this aspect. He appears burdened with some secret sorrow, which no one else can fathom. It seems he is always conscious of human sin, both in himself and others. It might be said he is in constant mourning for the human condition, so this is why he wears a veil made of black crape.