Focus on Cellulose ethers

How to prepare HPMC coating solution?

Preparing hydroxypropyl methylcellulose (HPMC) coating solutions involves multiple steps and requires careful attention to detail. HPMC is commonly used as a film coating material in the pharmaceutical and food industries. Coating solutions are applied to tablets or granules to provide a protective layer, improve appearance, and facilitate swallowing.

1. Introduction to HPMC coating:

Hydroxypropylmethylcellulose (HPMC) is a cellulose-based polymer derived from plant fibers. Due to its film-forming and thickening properties, it is widely used in film coatings in the pharmaceutical and food industries.

2. Required materials:

Hydroxypropyl methylcellulose powder
Purify water
Plastic or stainless steel containers
Stirring equipment (e.g. magnetic stirrer)
Measuring instruments (scales, measuring cylinders)
pH meter
Plastic or stainless steel coating pan
Hot air oven


Weigh the HPMC:

Accurately weigh the required amount of HPMC powder based on the desired coating formulation. Concentrations are usually between 2% and 10%.

Prepare purified water:

Use purified water to ensure it is free of impurities that could affect the quality of the coating. The water should be at room temperature.

Dispersion of HPMC:

Slowly add the weighed HPMC powder to the purified water while stirring continuously. This prevents clumps from forming.


Stir the mixture using a magnetic stirrer or other suitable stirring device until the HPMC powder is completely dispersed in the water.

pH adjustment:

Measure the pH of the HPMC solution using a pH meter. If necessary, the pH can be adjusted by adding a small amount of acid or base accordingly. The optimal pH for film coating is usually in the range of 5.0 to 7.0.

Moisturizing and aging:

The HPMC solution is allowed to hydrate and age for a specific period of time. This enhances film-forming properties. Aging time may vary but is typically in the range of 2 to 24 hours.


Filter the HPMC solution to remove any undissolved particles or impurities. This step is essential to obtain a smooth, clear coating solution.

Viscosity adjustment:

Measure the viscosity of the solution and adjust it to the desired level. Viscosity affects the uniformity and thickness of the coating.

Test compatibility:

Test the compatibility of the coating solution with the substrate (tablets or granules) to ensure proper adhesion and film formation.

Coating process:

Use a suitable coating pan and use a coating machine to apply the HPMC coating solution to the tablets or granules. Adjust pot speed and air temperature for optimal coating.


The coated tablets or granules are dried in a temperature-controlled hot air oven until the desired coating thickness is achieved.


Conduct quality control testing of coated products including appearance, thickness and dissolution properties. conclusion:

The preparation of HPMC coating solutions involves a series of precise steps to ensure the quality and effectiveness of the coating. Adherence to prescribed procedures and quality control measures is critical to obtaining consistent and reliable results in the pharmaceutical and food industries. Always follow Good Manufacturing Practices (GMP) and related guidelines during the coating process.

Post time: Jan-18-2024
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