All packages must contain and isolate a specific amount of product and must not allow the contents to leak or evaporate from the container. Many products must be protected from the chemical, physical and biological environment in order to function properly. For example, permanent hair colors must be protected from air or oxygen permeation through the package. If oxygen were to reach the hair coloring liquid, it would react chemically with the dyes to form the final oxidation color in the bottle, instead of on the hair (where hydrogen peroxide is the source of oxygen). Non-permeable containers must be used. Other examples of package protection include putting a UV sensitive formulation in an opaque container instead of a clear one, and using bath salts in a water vapor impermeable bottle to prevent the dry powder from caking.
When inspecting a glass bottle, which is rarely used these days, besides checking the dimensions, neck opening, freedom from flaws and filling capacity, the quality of the seal used to cap the container is of prime importance;glass is impermeable and product loss other than breakage is dependent upon the quality of the closure.
Plastic containers, unlike glass, can vary in rigidity. They can be nearly rock hard or pliable enough to dispense lotions with only a light squeeze. Plastic packages, of course, are more susceptible to evaporation and diffusion loss than glass or metal containers. They should be inspected for the following attributes:
• Dimensions and tolerances
• Volume and tolerances
• Color and surface finish
• Rocker bottoms
• Neck finish and trim
• Holes and plastic chips or flakes
• Minimum wall thickness and bottle weight
• Drop impact strength
• Distortion and stress or crack resistance
There is an array of general tests that are run on packaging materials. Some of these tests include:
• Leakage tests. Containers are stored upside down and on their sides at room and elevated temperatures and any loss of contents are noted. Also packages may be put in a partial vacuum to check for leakage.
• Weight loss tests. Containers are checked at elevated temperatures to determine the permeability to volatile substances such as water, alcohol and ammonia.
• Drop tests. A package is dropped from a fixed height onto a certain floor surface and is then examined for breakage or damage.
• Shipping tests. A dozen packages containing the product are boxed and shipped across the country and back. The carton is then opened and examined for damage. Instead of this test—or in addition to it—a vibrating table may be used. The packages are shaken for a specified time and then evaluated for damage.
Compatibility of the product with the package can be checked by simply immersing half of the packaging material in the product in a closed container. Any change in color, shape or texture of the packaging strip can be discerned by comparing it to the half which was untreated.
The container’s resistance to UV rays can be monitored on a sunny shelf or in the Fadeometer. Torque tests are run to check cap tightness. The tightness specification should be adequate to prevent leaking but it should not hinder cap removal.
The best way to evaluate these tests is to compare them to a similar competitor’s product, or to a like product from your own company where the stability history is known.