Pharma glass defects - 45. Malformed and Unfilled Finish

Welcome to Part 45  of an ongoing series examining visual defects that can occur in pharma glass vials based on the lexicon defined by PDA TR 43.  I’m covering two related yet distinct defects in today’s post for the sake of efficiency: 1) the “Malformed Finish” and 2) the “Unfilled Finish”.  As their names suggest, both defects are referring to an issue with the flange of the vial, otherwise known as the finish, crown, or lip.  Before I get into the details, let’s recall at a high level what is involved in manufacturing a converted tubular glass vial.  Heat and tooling is applied to sections of a long glass tube.  In doing so, molten glass can be shaped into individual vials that are separated from the remainder of the tube.  If you examine a drawing for a typical vial, you will notice that the neck and flange regions contain substantially more glass relative to the initial wall thickness of the tubing.  In other words, glass is fused back together to build up enough material to create the neck and flange of the vial, a process also known as “gathering”.  An “Unfilled Finish” defect (also known as a “Weak Contour”) is observed when the flange profile is incomplete (e.g., the lower radius of the flange is heavily rounded), perhaps indicating that insufficient material was gathered up to create a complete flange.  A “Malformed Finish” defect occurs when the sealing surface of the flange is not flat or heavily impaired in some way (see Footnote 1).  It could involve the gathering of too much glass or perhaps just improper forming of a sufficient quantity of glass.  Illustrations of both defect types are shown in Figure 1.

Figure 1.  Illustrated examples of Malformed Finish and Unfilled Finish defects.

Given their potential impact on container-closure integrity (CCI), the classification of both the Malformed Finish and Unfilled Finish defects follows a similar pattern.  A Malformed or Unfilled Finish that leads to a CCI failure is considered a Critical Defect.  A Major B classification is applied if: 1) the Malformed Finish is present but CCI is still maintained or 2) the Unfilled Finish exceeds dimensional tolerances for the flange or flange radii (see Footnote 2).  An Unfilled Finish that does not meet the conditions for a Major B defect is otherwise considered an Acceptable Imperfection.  However, the Malformed Finish does not allow for an Acceptable Imperfection classification according to PDA TR 43.  This brings up an interesting situation that can lead to potential quality-related conflicts between a glass supplier and the end user.  As I’ve previously noted, there is some overlap in the definitions of an Unfilled Finish, a Malformed Finish, and a Wavy Top defect.  Two of these three defects (Unfilled Finish and Wavy Top) do allow for an Acceptable Imperfection classification.  One could imagine how these differences could create conflicting incentives between the supplier and customer to arrive at a particular conclusion.  It leads to a point that I’ve raised repeatedly in prior posts – alignment between suppliers and end users on the methods used to identify and classify defects.

Questions or comments? – please leave them below or feel free to directly contact me.

Footnotes

1.     The description of a Malformed Finish also has some similarity to the “Wavy Top”, another defect involving a flange sealing surface that is not properly formed.  What’s the difference?  I interpret a Wavy Top as being a more subtle situation involving a rippled surface, while a Malformed Finish is a more serious impairment.

2.     It’s not explicitly stated in PDA TR 43, but I’m assuming that the Major B defect classification for an Unfilled Finish also means by definition that the CCI is still maintained despite the flange dimensions being out of spec.

About the Author

Matthew Hall is Technical Affairs Director for Corning Pharmaceutical Technologies, a manufacturer of primary glass packaging for parenteral drug products.  Based in upstate New York, Dr. Hall serves as a technical expert supporting business operations, sales, and marketing and educating customers on pharmaceutical glass packaging.  He is a member of the Parenteral Drug Association and the International Society of Pharmaceutical Engineering.