text: In 1928, German chemist H. O. Albrecht found that blood, among other substances, enhanced the luminescence of luminol in an alkaline solution of hydrogen peroxide.  In 1936, Karl Gleu and Karl Pfannstiel confirmed this enhancement in the presence of haematin, a component of blood.  In 1937, German forensic scientist Walter Specht made extensive studies of luminol's application to the detection of blood at crime scenes.  In 1939, San Francisco pathologists Frederick Proescher and A. M. Moody made three important observations about luminol:
  # although the test is presumptive, large areas of suspected material can be examined rapidly;
  # dried and decomposed blood gave a stronger and more lasting reaction than fresh blood; and
  # if the luminescence disappears, it may be reproduced by the application of a fresh luminol-hydrogen peroxide solution; dried bloodstains may thus be made luminescent repeatedly.