Carbolfuchsin used in the original acid fast stain consisted of 0.3 g basic fuchs in 10 ml 95% ethanol 5ml phenol and 95 ml water . the recipe for the kingpin modification is 4 g basic fuchsin in 20 ml ethanol 8g phenol and 100 ml water . the original acid fast stain require heating the smear to force the carbolfuchsin into the wall. why can heat be eliminated in the kingpin modification that you used ?

The reason is that, the mycobacterium wax-like lipid such as Nocardia is not susceptible to staining or decolorization, hence, the heat allowed penetration of the stain. Also, the kinyoun modification does not require heat because a more concentrated fuchsin is used

Explanation:

The Kinyoun method or stain, otherwise known as cold method, is a procedure used to stain acid-fast species of the bacterial genera Mycobacterium and Nocardia and the apicomplexan genus Cryptosporidium.

Developed by Joseph Kinyoun, researched that, given particular species of bacteria that have a waxy lipid called mycolic acid, in their cell walls, this allow them to be stained with Acid-Fast better than a Gram-Stain.

This is due to the fact that mycobacteria, has the special ability to resist staining or decolorization byacid-alcohol, hence, it was termed acid-fast.

The procedure involves the application of a primary stain (basic fuchsin), a decolorizer (acid-alcohol), and a counterstain

Therefore, in this case, the reason the heat can be eliminated in the kingpin modification is that, the mycobacterium wax-like lipid such as Nocardia is not susceptible to staining or decolorization, hence, the heat allowed penetration of the stain. Also, the kinyoun modification does not require heat because a more concentrated fuchsin is used.