Sensient

Trouble Shooting

Our technical expertsare available to help you solve your coating challenges at any time:

pharma.info@sensient.com
800-325-8110

PROBLEM
The coating surface is rough: lacks smooth and glossy finishes
CAUSE
Low atomization air and close gun to bed distance
SOLUTION
Increase atomization air and adjust gun to bed distance
pill_uniformityPROBLEM
Two different color tones from tablet to tablet
CAUSE
Poor solution mixing, poor spray pattern, high solution solids, slow pan speed, low film coating weight gain, close gun to bed distance, colorant choice is poor
SOLUTION
Increase solution mixing, increase pattern air, decrease solution solids, increase pan speed, increase weight gain, increase gun to bed distance, use lake pigments in formulation
PROBLEM
Coating fills into the logo or the bisect may become narrowed
CAUSE
Poor formulation, poor logo design, poor coating application, poor atomization pressure, high solution solids, spray rate too high
SOLUTION
Increase plasticizer concentration, decrease solution solids, increase atomization
PROBLEM
Dark and light patches on the tablet surface
CAUSE
Colorant migration during granulation, colored active ingredients used with non-colored excipients, high inlet temperature degrades actives – induces color changes, liquid plasticizer penetration into the core during coating
SOLUTION
During granulation, add colorant ingredients with the binders followed by the addition of granulating liquid – then mix thoroughly, reduce inlet temperature to prevent core active degradation, increase opacity in film coating, seal coat core, optimize coating plasticizer – Call Sensient for Technical Support to choose the right coating formulation
PROBLEM
Fine cracks observed on the upper or lower sides of coated tablets
CAUSE
Greater internal stress, poor film tensile strength
SOLUTION
Adjust polymer MW and plasticizer type to decrease internal stress effects on film, decrease temperatures of the tablet bed, adjust relaxation time after tablet compression before coating
PROBLEM
Film is pulled from the core surface after tablets stick together
CAUSE
Inefficient drying, over wetting from high spray rates, poor coating adhesion
SOLUTION

Reduce spray rate, increase inlet temperature, increase airflow volume, increase pan speed, increase film adhesion, increase / optimize atomization air flow
PROBLEM
Chipping occurs on the edges or logo areas
CAUSE
Excessive attrition during coating, core is friable
SOLUTION
Decrease pan speed, increase core hardness, decrease pan load, increase film strength, adjust baffle height – if possible
PROBLEM
Film detachment forms a blister
CAUSE
Over heating during spraying
SOLUTION
Decrease inlet temperature, decrease spray rate
PROBLEM
Over-wetted tablet surface with inadequate drying
CAUSE
Fast spray rate, inadequate drying, poor core formulation
SOLUTION
Decrease spray rate, increase inlet temperature, improved core strength
PROBLEM
Tablets stick together
CAUSE
Poor suspension evaporation
SOLUTION
Reduce spray rate, increase pan speed, increase inlet temperature to increase drying, increase atomization air pressure
PROBLEM
Coating texture appears like an orange’s texture
CAUSE
Fast drying, slow spray rate, high solution viscosity
SOLUTION
Either decrease the inlet temperature or increase the spray rate, dilute the solution to decrease the solution viscosity, optimize gun
PROBLEM
Tablet surface divots – pitting
CAUSE
Poor film coalescence (film spreading), high core temperature melts core ingredients/materials
SOLUTION
Decrease inlet temperature, control drying temperatures
PROBLEM
Exposed areas of the core after coating
CAUSE
Coating solution penetrates into the core
SOLUTION
Decrease spray rate, optimize drying efficiency
PROBLEM
White specs or film haziness
CAUSE
High coating temperatures, temperature is above the thermal gelation temperature of the polymer
SOLUTION
Decrease inlet temperature, modify formulation to decrease gelation temperature of the polymer
PROBLEM
Coating peels away from the core surface
CAUSE
oor coating formulation – plasticization or adhesion, high coating temperatures, cores are pre-warmed too long, core formulation
problems
SOLUTION
Increase coating formulation adhesion and plasticization, decrease inlet temperatures, decrease pre-warming time, decrease pan speed, decrease spray rate, optimize core formulation