Chances are good that glass containers never receive a second thought, but simply sat in your refrigerator or medicine cabinet or on the pantry shelf. Knowing your glass bottles, jars, jugs, and vials is important if containers are your business! At Freund we love Glass and are taking a moment to share our knowledge about glass types and terminology. Freund Container is an industry leader when it comes to glass with the broadest selection at unbeatable prices.
Types of Glass: Glass containers are made from silica sand, soda ash, limestone, alumina and other additives as needed. There are three different types of glass.
Type I – A borosilicate formulation, this type is usually reserved for parenteral (injectable) products, particularly those that are alkaline in nature. It is 10 times more durable than soda glass.
Type II – A soda-lime glass treated with sulfur in the annealing phase to reduce alkali solubility. It is used for parenterals – sometimes alkaline, but more likely acidic or neutral.
Type III – A regular soda lime (flint) glass that has been tested and shown to be at or below a specified extractives level. It is intended for more sensitive products, but usually is not used for parenterals.
Glass Container Terminology: Blown glass containers tend to fall into two categories: Narrow Neck and Wide Mouth Jars. Most commonly glass is found in two different colors, flint – clear or amber – brown color. Also, glass can be found in cobalt blue or sometimes with a greenish tint. There are secondary processes that can be done to frost the glass or tint custom colors. As with most packaging forms, there’s a distinct terminology associated with blown glass containers. Each term will be explained and Figure 1 diagrams the locations of the points that will be explained.
Sealing Surface – The flat, circular top surface of the finish in which the closure will form a seal. It’s also termed the “land”. If this is not flat, the container could leak.
Finish – The top part of the container, above the neck, shaped to accommodate a specific closure.
Thread – A small spiral-shaped protruding glass ridge on the finish of a container intended to mesh with a similarly sized screw-type closure to seal the container.
Neck – That portion of the container that is above the shoulder and below the finish. The neck is where the cross-section of the bottle grows smaller to join the finish.
Neck Ring or Bead – Protruding ring just above the neck-ring parting line. All glass bottles have this so they can be removed from the machine.
Mold Seam – The slight vertical ridge of glass that runs through the neck ring and the rest of the finish. The seam indicates where two halves of the finish molds were joined.
Shoulder – That part of the bottle between the main body and the neck.
Body – The main part of the bottle where the sidewalls are usually vertical.
Bottom – The entire lower part of the bottle below the sidewalls. The bottom includes the heel, base and push-up. The bottom may have letters and symbols molded into it that indicate the number of the mold cavity that produced the container and the manufacturer. The manufacturer symbol is called a “punt mark”. The bottom also may have a small projection that serves as a registration device for labeling and decorating equipment. The device also can take the form of a small recess along the heel of the container. This is also a good spot for a customer name or company logo.
Heel – That lower part of the bottle where the glass in the sidewall turns from vertical to horizontal. The heel joins the sidewall to the bottom-bearing surface and may have a small recessed spot that serves as a registration device for labeling and decorating equipment.
Base – An even bearing surface that forms a ring around the outside of the bottom upon which the bottle rests. This ring usually is given a stippled finish in the mold to mask scratches that occur during handling and concentrate abrasions on the stronger high points of this raised pattern, thus, preventing the container from being weakened. The base is inside and underneath the heel and surrounds the push-up.
Push-up – An inward dome in the center of the base. The resulting ring around the outside of the bottom provides an even bearing surface upon which the bottle rests.
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