Problems in Sugar Coating of Tablets
Common Problems that can occur during the sugar coating process and their solutions
- 1. Chipping of the tablet coating
- 2. Cracking
- 3. Non-drying of the coating
- 4. Twinning
- 5. Uneven colouring
- 6. Blooming
- 7. Sweating
- 8. Marbling
1. Chipping of the tablet coating
- This is often caused by a low concentration or absence of polymer
- add more polymer to the coating solution.
- Another cause is the excessive use of pigments and insoluble fibres
- reduce the number of fillers
2. Cracking
- Expansion of the tablet during or after coating caused by stress relaxation or moisture absorption –
- consider the use of seal coat or extend the time between the sugar coating and compaction
3. Non-drying of the coating
- Excessive presence of invert sugar –
- avoid the excess heating of the sucrose syrup under acidic conditions
4. Twinning
- High edge walls/flat surface
- modify or alter the punch design
5. Uneven colouring
- Poor distribution of coating solution
- add sufficient liquid and ensure that it is fully mixed
- Colour migration due to under/rapid drying
- optimize the drying condition and use pigments
- Uneven sub coat layer
- achieve the required smoothness during the sub coat application
- Wash back of pigment colour coating
- avoid excess colour coating liquid
- Excessive drying between colour application
- optimize the drying conditions
6. Blooming and Sweating
- Extra moisture in the finished tablet coat
- dry properly to ensure the appropriate moisture level
7. Marbling
- Uneven coating surface
- make sure to achieve smooth coating before the polishing step
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