Procedure

Dissolve a pair of Bluestar reagent tablets in 125mL of distilled or demineralised water in a spray bottle equipped with a fine mist atomiser.  Use within 8 hours of mixing.  An intense blue (430nm) luminescence occurs (visible in semi-darkness) when the solution comes into contact with blood residues.  Very small quantities of blood will provoke a reaction, and the luminescence will generally last for several minutes.  The solution can be re-applied several times to the same area.  This method works well with non-human as well as aged blood residues.  One pair of tablets will provide enough solution (125mL) to examine a surface area of up to 25m².

Suggested Approach

Apply dilute animal blood (MED25.10 or from meat) to pieces of fabric, paper or an absorbent surface such as natural wood.  Allow the blood to dry then lightly spray with the mixed reagent system in dim light.  For best results, allow your eyes to become accustomed to the low light conditions in advance.  Compare the results to similar stains made with food dyes.

How Does It Work?

In alkaline conditions, luminol reacts with hydrogen peroxide to produce an unstable intermediate that sheds its excess energy as light.  This reaction is greatly accelerated in the presence of haem, an organic iron complex found in haemoglobin.  Haem is such a stable and effective catalyst that even very dilute and aged blood residues can be detected.