- Types of glass include:
- Type I – Borosilicate Glass (also known as Pyrex)
- Type II – Treated Soda-Lime Glass
- Type III – Soda-Lime Glass or Soda-Lime-Silica Glass
- Type III is the most common type of glass bottles.
Type I is the most durable glass.
Type I – Borosilicate Glass
Type I Borosilicate glass offers the best resistance to thermal shock and also superior chemical resistance. This class of glass represents the least reactive glass containers available. Type I glass offers superior durability, chemical and heat resistance. It is commonly used for chemical laboratory equipment.
Borosilicate glass contains a significant amount of boric oxide, aluminum oxide, and alkali and/or alkaline earth oxides. Borosilicate glass has a high hydrolytic resistance due to the chemical composition of the glass itself.
Typically, this glass can be used for most applications, including packaging for parenteral (injectable) and non-parenteral products. Type I glass may be used to package acidic, neutral and alkaline products. Water for injection, un-buffered products, chemicals, sensitive products and those requiring sterilization are commonly packaged in Type I borosilicate glass. Type I glass can be subject to chemical attack under certain conditions, thus container selection must be made carefully for very low and very high pH applications
Type II – Treated Soda-Lime Glass
Type II glass is type III glass which has been surface treated to improve the hydrolytic stability from a moderate to a high level. Type II glass containers are suitable for acid and neutral preparations both for parental and other use. The outer surface of glass containers may also be treated to reduce friction or for protection against abrasion or breakage. Test methods and specification limits for determining the chemical resistance of glass can be found in the current revision of the U. S. Pharmacopeia, section: Containers – Glass
Type III – Soda-Lime Glass
Type III soda-lime glass is a silica glass containing alkali metal oxides. Soda-lime glass exhibits moderate chemical resistance and moderate hydrolytic (water) resistance. Soda-lime glass is inexpensive, chemically stable, and ideal for recycling as the glass can be re-melted and re-formed multiple times.
Type III glass is commonly used for beverages, foods and pharmaceutical preparations. Type III glass is not suitable for autoclaved products because the autoclaving process will accelerate the glass corrosion reaction. Dry heat sterilization processes are typically not a problem for Type III containers. Amber glass is created by the addition of iron oxide. Amber glass is formulated to absorb light in the ultra violet region of the electromagnetic spectrum and is used to package light sensitive products
Lead “Crystal” Glass
Lead Glass or Crystal is a variety of glass used for decorative glass containers. Lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% weight lead oxide, while modern lead crystal contains a minimum of 24%. Due to the potential health risks of lead, true lead crystal glassware is now rare. Lead-free Crystal Glass is commonly used to manufacture glassware and is referred to as “Crystal”. In lead-free crystal glass, barium oxide, zinc oxide, or potassium oxide are used in lieu of lead oxide. Lead-free crystal has a similar refractive index (sparkle) like lead crystal, but it is lighter and it has less dispersive power.
Leaded crystal wineglasses and decanters are generally not considered to pose a significant health risk, provided that beverages are not stored in these containers for more than a few hours. Lead glass decanters will leach lead into the beverages contained within the decanter over time.