The USP Specifications for Type I Glass Containers

The United States Pharmacopeia (USP) is a public agency that sets standards for medicines, both prescription and over-the-counter, made or sold in the United States.

The USP also maintains standards for pharmaceutical containers. The USP has four different classifications for glass containers, ranging from Type I to Type NP. Type I is the best glass container. It is the least reactive with its contents.

Composition

• Type I glass containers are typically made of borosilicate glass. This glass has a high silicone content, and it is the least reactive, which means that the glass is least likely to have a chemical reaction with whatever you place inside it. The glass will not leech into its contents, which can happen with a more reactive glass type.

Temperature resistance

• Type I glass containers are highly resistant to temperature changes. They have a low coefficient of expansion, which is the fractional change in the glass length per degree of temperature change: 33 or 51 for clear glass containers, and 51 for amber glass containers. In addition, Type I containers have a high strain point, which is the maximum temperature you can safely heat the glass to when you use it. You can heat clear Type I containers to 515 degrees Celsius and amber Type I containers to 535 degrees Celsius.

Strength

• Type I containers have a compressive strength (how much compression pressure the glass can take before it breaks) of 42,800 psi. They have a flexural strength (how much flexural pressure the glass can take before it breaks) of 1,000 psi.

Appearance

• Type I containers typically come in two color types: clear and amber. Depending on their thickness, clear containers transmit up to 90 percent of visible light, while amber glass containers transmit roughly 80 percent of visible light (mostly closer to the infrared spectrum).