Congo Red Puchtler kit is used for staining amyloids (amorphous clusters) in histology sections. Despite their variable protein composition, amyloid deposits are linked by fibril beta-sheets formation. Congo Red dye binds to fibrils and form a regular pattern of dye molecules during the process. The structural regularity of the dye under polarized light demonstrates double refraction of light by displaying green coloration. High pH level and ionic strength of solutions according to Puchtler achieve higher dye specificity to amyloid.