how did the blood stain proov to be persistient?

what was the history behind the blood stain as given by mrs umney?

Mrs. Umney explains to the Otis family that the bloodstain was caused when Sir Simon shot his wife Lady Eleanore in the year 1575. This bloodstain had been on the living room carpet since then and had always remained a curious attraction to tourists. However, Washington Otis was prompt to remove the stain with "Pinkerton's Champion Stain Remover and Paragon Detergent" powder. Nevertheless, the Ghost would ensure that the stain kept on returning everyday, in spite of Washington Otis' best efforts.He would steal paints from Miss Virginia's paint box to replenish the stain. This resulted in the stain being of a variety of colors, like vermilion and emerald green. Although, the efforts of the Ghost resulted in hilarity, it conclusively proved that Canterville Chase was haunted.