Glass is one of the most easily identifiable forms of packaging out there, but did you know there are actually many different types of glass? Well, sit tight because in this lesson, we’re going to take a look at the three most common commercially-used types of glass!
Glass containers are classified by a common standard set by the United States Pharmacopeia (USP). This standard regulates the chemical composition and chemical durability of the glass, or the glass’ ability to resist attack by the contents of the container.
First, we have borosilicate glass, or Type I glass:
It has the highest chemical resistance of all glass types and better than average thermal shock resistance.
It meets the highest standard for limiting the amount of glass components that leach out of the glass into the product.
While its high melting point is an advantage for the end user, it serves as a disadvantage during forming, as it demands specialized heating processes during manufacturing.
Type I glass has the ability to withstand wide temperature swings while remaining inert, which makes it perfect for pharmaceuticals, laboratory glassware, and cookware.
Next, we have Type II glass, or de-alkalized soda-lime glass:
Type II glass offers a cheaper manufacturing alternative to Type I, while still providing some of its beneficial qualities.
Type II glass is soda-lime glass, treated with sulfur dioxide or sulfur trioxide to reduce component leaching and improve the glass’ chemical resistance.
This makes it safer than Type III for pharmaceutical packaging, but with one caveat—the solution inside cannot have a pH over seven during its shelf life.
The sulfur dioxide gas treatment loses efficacy over time, so these bottles are strictly a one-time use package.
Type II glass is rarely used these days, only serving the functions of a Type I glass in impoverished countries, where its cheaper cost to manufacture makes it the most economical option.
Lastly, there is Type III, or soda-lime glass:
This is the most prevalent type of glass for consumer use, making up nearly 90% of all glass manufactured in the world.
It is classified by the United States Pharmacopeia as nonparenteral or NP, meaning it can be used for medications that are to be taken orally or via topical application.
Soda-lime glass is inexpensive to manufacture and easy to recycle thanks to its low melting point.
While it does not have the chemical resistance of Types I or II or the thermal shock stability of Type I, it is relatively inert and strong enough to offer a good solution for most packaging needs.
The most common uses for Type III glass are food jars, beverage bottling, window glass, and decorative accessories.
So, when you’re planning on packaging with glass, be sure the type of glass fits your end use. If it needs to have a long shelf life, withstand huge temperature swings, and not affect your product chemically in any way, you’ll want Type I, borosilicate glass.
If you need more affordable pharmaceutical packaging for a product with short shelf-life and are not concerned with the reusability of the package, then Type II, de-alkalized soda-lime glass, is for you. And really, for pretty much anything else, you’ll be using Type III, soda-lime glass.
Thanks for checking out this short lesson! For more lessons on glass and other packaging materials, visit our website at packagingschool.com. As always, be sure to subscribe to the Packaging School on YouTube for more educational videos just like this!
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