Congo Red dye forms non-polar hydrogen bonds with amyloid and red to green birefringence occurs when viewed by polarised light due to parallel alignment of the dye molecules on the linearly arranged amyloid fibrils. The Alkaline Congo Red Technique uses high concentrations of sodium chloride which act as ionic competitors for the dye thus eliminating background electrochemical (polar) staining while enhancing the hydrogen (non-polar) binding of Congo Red and amyloid.