Steps of sugar coating of tablet:-
i) Sieving
ii) Sealing
iii) Sub-coating
iv) Syrup coating
v) Finishing
vi) Polishing
i) Sieving :- The tablets to be coated are shaken in a suitable sieve to remove the fine powder or broken pieces of tablets
ii) Sealing :-
Sealing is done to ensure that a thin layer of water proof material, such as, shellac or cellulose acid phthalate is deposited on the surface of the tablets.
The shellac or cellulose acid phthalate is dissolved in alcohol or acetone & its several coats are given in coating pan.
A coating pan is made up of copper or stainless steel.
The pan is rotated with the help of an electric motor.
iii) Sub coating :-
In sub coating several coats of sugar & other material such as Gelatine, Acacia etc. are given to round of tablet and to help in building up to tablet size.
Several coats of concentrated syrup containing acacia or gelatine are given.
After each addition of the syrup, dusting powder is sprinkled.
The dusting powder is a mixture of starch, talc & powdered acacia.
iv) Syrup coating :-
This is done to give sugar coats, opacity &color to tablets
Several coats of the syrup are applied
Coloring materials & opacity agent are also added to the syrup
The process of coating is repeated until uniform colored tablets are obtained
v) Finishing :-
Three to four coats of sugar are applied in rapid succession without dusting powder and cold air is circulated to dry each coat. Thus forms a hard smooth coat
vi) Polishing :-
Beeswax is dissolved in volatile organic solvent & a few coats of it are given.
The finished tablets are transferred to a polishing pan is rotated at a suitable speed so the wax coated tablets are rubbed on the canvas cloth.
This gives a proper shining to the tablets