Some Common Tablet Coating Defects

Coating process involves a lot of problems. Below are some widely found tablet coating defects and their causes listed.

Picking & Sticking
This defect is caused when the tablets get over wet or are under dried or if the tablet quality is poor. This type of defect is also caused when coating takes off a piece of tablet from is basis.

 

Bridging
This defect occurs when the coating material fills over the lettering or the logo of the tablet. Bridging is a type of defect caused mainly due to improper application of the solution, poor design of the tablet embossing, high coating viscosity, high percentage of solids in the solution, or improper atomization
pressure.

Capping
The main cause of this defect is the improper compression of the tablet. This defect will not be revealed unless the coating process is initiated. It is important to ensure that the tablets are not excessively dried in the pre-heating stage. Excessive heating will result in making the tablets brittle and nurture capping.

Erosion
It occurs because of soft tablets, an over-wetted tablet surface, inadequate drying, or lack of tablet surface strength.

Twinning
This defect is generally found in capsule shaped tablets. When two capsule shaped tablets stick with each other, twinning defect occurs. However, this problem can be solved by balancing
 the pan speed and spray rate.

Peeling & Frosting
In this type of coating defect coating peels away from the surface of the tablet. This occurs when the peeling solution does not locks with the surface of the tablet. A defect in coating solution, over-wetting, or high moisture content in the core of the tablet result in peeling of the coating.

Chipping
Chipping is caused due to high pan speed, a friable tablet core, or a coating solution that lacks a good plasticizer.

Motted Color
Motted color of the tablet occurs when the coating solution is not prepared properly or the real spray rate is different from the target rate. This can also happen if the tablet cores are cold.

Orange Peel
Orange peel, as the name suggests is the coating texture which is similar to the surface of an orange. Orange peel usually occurs when high atomization pressure combine with high spray rates.