This document discusses common film defects that can occur during the tablet coating process. It describes 14 different defects - blistering, blooming, blushing, bridging, capping, chipping, cracking, mottling, orange peel effect, picking, pitting, sticking, twinning - and provides the causes and remedies for each one. The defects result from issues like high temperatures during drying, improper formulation, inadequate spreading of coating solution, or excess moisture in granules. Suggested remedies include using milder drying conditions, reducing viscosity or plasticizer content, controlling drying temperature, and improving lubrication.

1. FILM DEFECTS IN
TABLET COATING
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Raksha Laxman Mhetre
Modern College of Pharmacy (for Ladies),
Pune-412105

2. 1. Blistering
It is a film detached from the tablets surface.
Causes:
High temperatures during the drying process, spraying
stage or at the end of the coating process.
Remedies:
Use mild drying conditions, Ensure moderate
temperatures at other stages of the coating process.
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3. 2. Blooming
Fading or dulling of a tablet colour after a prolonged
period of storage at a high temperature.
Causes:
• Use of high amount of plasticizer
• Using plasticizer with a low molecular weight
Remedies:
• Decrease the concentration of plasticizer
• Increase the molecular weight of the plasticizer in the
polymer
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4. 3. Blushing
It is a haziness or appearance of white specks in the
film.
Causes:
• High coating temperature may causes precipitation
of polymer on tablet coating.
Remedies:
• Decrease the drying temperature to avoid
precipitation of polymer.
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5. 4. Bridging
It is coating fills in the letter or logo on the tablet.
Causes:
• Improper formulation
• Poor logo design
• High coating viscosity
Remedies:
• Reduce the viscosity of coating solution
• Increase the plasticizer content
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6. 5. Capping
The upper and lower crown of the tablet separates
horizontally from the main body.
Causes:
• Due to air entrapment
• Concave punches produce capping
Remedies:
• Use of flat punches
• Use of hygroscopic substance
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7. 6. Chipping
It is the defect where film becomes chipped and
dented at the edges of the tablet.
Cause:
Excessive attrition during coating process
Remedy:
Increase hardness of the film
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8. 7. Cracking
Small fine cracks observed on the upper and lower
central surface of tablets.
Cause:
Due to the use of high molecular weight polymers
Remedies:
• Use low molecular weight polymers
• Adjust the plasticizer & pigment concentration
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9. 9. Mottling
Unequal distribution of colour on a tablet, with light
or dark spots.
Cause:
Coloured drug whose colour differs from the colour of
excipients
Remedy:
Use appropriate colour
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10. 10. Orange peel effect
It refers to a coating texture that resembles the surface of
an orange.
Cause:
Inadequate spreading of coating solution before drying
Remedy:
Thinning the solution with additional solvent
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11. 11. Picking
Small amount of material from the tablet is sticking to
and being removed off from the tablet surface by a punch
face.
Causes:
• Excessive moisture in granules
• Improper lubrication
Remedies:
• Properly dry the granules
• Increase the lubrication
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12. 12. Pitting
It is a defect whereby pits occur in the surface of tablet
core.
Cause:
Temperature of tablet core is greater than melting point of
the materials used in tablet formulation.
Remedy:
Control drying temperature
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13. 13. Sticking
Tablet material adhering to die wall.
Cause:
Improperly dried or improperly lubricated granules
Remedies:
• Dry the granules properly
• Increase or change the lubricant
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14. 14. Twinning
Two tablets stick together and it is most common in
capsule shape tablets.
Cause:
High spray rate causes over wetting tablets.
Remedies:
• Reducing spray rate
• Increasing pan speed
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