TABLET COATING PROBLEMS

BLISTERING:- It is the  detachment of film from the tablet substrate as the elasticity of surface film compromised.

Cause- generally occur due to higher temperature during various stages of coating.

CHIPPING: It is generally a edge phenomena in which at the edge of tablet the surface film chipped off.

Cause decrese in rotation speed of pan, poor coating solution.

CRATERING: It is defect in which a defect in film coating leads to craters appearing exposing the tablet surface.

Cause insufficient drying time, high volume of coating solution used

PICKING: It is defect where a surface film is pulled away from the surface when the tablet sticks together and then part due to being detached away from the core. 

Cause over wetting of tablets due to polymer solution, improper drying.

PITTING: It is a defect in which deformation occur or pitts formation occur in the surface of a tablet core without any visible disruption of the film coating.

Cause it generally occur when the temp of core of the tablets generally higher than the melting points of material used in it. 

BLOOMING: It is defect where dullness in coating colour of tablet occur after  prolonged storage at high temperatures.

Causes use of low molecular weight plasticizer, 

BLUSHING: It is defect in which whitish specks or haziness occur  in the film.

Cause occur due to the high caoting temp. Leads to percipitation of polymers on surface. 

COLOUR VARIATION: A defect which involves variation in colour of the film.
Cause poor mixing, uneven spray pattern, migration of dyes during drying etc.

Infilling- it refers to filling of intagliations(distinctive words or symbols on tablet surface)

Cause due to accumulation or settling of foam in intagliations caused due to air spraying 

ORANGE PEEL EFFECT: It is surface defect resulting in appearence of an orange peel having rough and nonglossy texture.

Cause too high spray pressure, poor tablet composition, rapid drying etc

CRACKING/SPLITTING: It is defect in which the cracks in the films occur across the crown of the tablet (cracking) or splits around the edges of the tablet (Splitting).

Causes occur when the internal stress of the film exceeds the tensile strength of fim, use of high molecular weight polymers.

Links 

http://www.pharmainfo.net/tablet-ruling-dosage-form-years/problems-tablet-manufacture-and-related-remedies/tablet-coating-problems

https://www.lfatabletpresses.com/articles/different-tablet-coating-defects-and-remedies