20. Container Closure Integrity

A method for demonstrating appropriate environmental protection for capping aseptically filled and plugged vials. - more Evaluation of a container closure integrity test model using visual inspection with confirmation by near infra-red spectroscopic analysis. - more Contamination of Flexible Pouches Challenged by Immersion Biotesting - more Development of a dye ingress method to assess container-closure integrity: correlation to microbial ingress. - more Introduction to Laser-Based Headspace Inspection and the Application to 100% Container Closure Inspection of Sterile Pharmaceutical Containers - more Application of fluid modeling to determine threshold leak size for liquid foods. - more Bioaerosol Exposure Method for Package Integrity Testing - more Pharmaceutical container/closure integrity. VI: A report on the utility of liquid tracer methods for evaluating the microbial barrier properties of pharmaceutical packaging. - more The pharmaceutical vial capping process: Container closure systems, capping equipment, regulatory framework, and seal quality tests. - more Leak testing in parenteral packaging: establishment of direct correlation between helium leak rate measurements and microbial ingress for two different leak types. - more ! NEW ! Evaluation of Container Closure System Integrity for Storage of Frozen Drug Products: Impact of Capping Force and Transportation - more ! NEW ! Quantifying the Vial Capping Process: Residual Seal Force and Container Closure Integrity - more ! NEW ! Holistic Considerations in Optimizing a Sterile Product Package to Ensure Container Closure Integrity - more ! NEW ! Method Development for Container Closure Integrity Evaluation via Headspace Gas Ingress by Using Frequency Modulation Spectroscopy - more ! NEW ! Container Closure Integrity Testing—Practical Aspects and Approaches in the Pharmaceutical Industry - more ! NEW ! Artificial Leaks in Container Closure Integrity Testing: Nonlinear Finite Element Simulation of Aperture Size Originated by a Copper Wire Sandwiched between the Stopper and the Glass Vial - more 1. A method for demonstrating appropriate environmental protection for capping aseptically filled and plugged vials. Arnold JF, Price JM PDA J Pharm Sci Technol. Abstract Conventional aseptic filling of drug product into vials ultimately includes a step that requires time and travel from the stoppering stage to the capping/crimping stage. Lyophilized product necessarily includes a partial stoppering step and, therefore, Grade A conditions. The level of environmental control that is required to protect the contents of fully stoppered, but uncapped, vials of sterile product from microbial contamination hasn't been formally defined. There is considerable range of opinion regarding this topic. This is the result of the lack of data that indicates the level of protection afforded by vials that are closed with a stopper, but that have not yet been capped. In order to provide some insight into the level of environmental control that is appropriate for vials at this stage of production, studies were conducted that consisted of exposing stoppered, uncapped vials containing sterile microbiological media to an aerosolized microbial challenge. The test samples were selected and assembled in such a way that a range of container/closure presentations was simulated. Furthermore, a microbial challenge was selected that was in excess of the environmental conditions to which product vials would be exposed. The results of this testing indicated a high level of confidence that stoppered, uncapped vials exposed to microbiologically challenging conditions would be expected to maintain the sterility of their contents.

2. Evaluation of a container closure integrity test model using visual inspection with confirmation by near infra-red spectroscopic analysis. Birrer GA, Liu J, Halas JM, Nucera GG. PDA J Pharm Sci Technol.  Abstract The objective of this study was to evaluate a novel test model involving an easy and rapid method to assess parenteral container/closure integrity. In this study, an extremely hygroscopic powder (methacholine chloride) was filled into the test vial/closure combination and served as an indicator of water vapor ingress into the package through either the stopper/glass interface and/or permeation through the closure. A visual means of detection was used initially, as the powder liquefies upon contact with a high-humidity environment. A further level of sensitivity was gained by using Near Infra-Red (NIR) spectroscopy to confirm that no additional water vapor was detectable in the test vials after being subjected to autoclave (worst-case water ingress) treatments. After two sequential autoclave cycles, none of the samples in the pilot study showed liquification of the indicator powder. This indicated that there was negligible ingress of water vapor, and therefore, the container/closure combination provided an adequate barrier to moisture ingress at the stress temperature and pressure conditions studied. The sensitivity of the NIR water ingress detection method was shown to be in the range needed for an acceptable vial integrity test. In conclusion, the model evaluated in this study can be used as an easy, rapid, and non-destructive closure integrity evaluation test. The use of such a NIR spectroscopy method would be immediately and directly amenable to the evaluation of vial integrity of dry powder-filled and lyophilized products, or can be used indirectly as shown in this study to assess container closure integrity for liquid-filled parenteral vial closure systems.

3. Contamination of Flexible Pouches Challenged by Immersion Biotesting Barbara A. Blakistone, Scott W. Keller, Joseph E. Marcy, Walter H. Carten https://www.researchgate.net/publication/233552712_... Abstract Immersion biotesting has long been used to challenge packages, particularly cans, for pinholes and channel leaks. Such testing for all types of plastic packaging may not be appropriate because some packages (e.g., aseptic, hot fill) are not exposed to water. As the food-packaging industry develops alternative environmental biotests there is a need to benchmark them against traditional immersion testing. The purpose of this research was to examine the threshold of critical-defect dimensions using artifically created channel leaks of 10 and 20 μm and 5- and 10-mm lengths sealed into plastic pouches which were subsequently tested by immersion at 102 and 106 CFU of motile and nonmotile Pseudomonas fragi TM849 per ml. Forty-four percent (44%) of the pouches tested became contaminated, indicating the threshold defect value is below 10 μm. Microbial ingress was significant (P < .05) for motile test organisms with a concentration of 106 CFU/ml. The interaction of concentration and time was also significant at 102 CFU/ml at 30 min exposure and 106 CFU/ml at 15 min. Channel length was not statistically significant. The markedly greater contamination rate using immersion testing versus that of aerosol testing highlights the importance of using test methods that reflect environmental exposure conditions of the packages.

4. Development of a dye ingress method to assess container-closure integrity: correlation to microbial ingress. Burrell LS, Carver MW, DeMuth GE, Lambert WJ. PDA J Pharm Sci Technol. Abstract To demonstrate maintenance of parenteral product sterility, container-closure integrity over the shelf life of the product is critical. In the past, sterility testing has been used to ensure closure integrity. However, because of the limitations associated with sterility testing, there is a need for an improved method for evaluating container-closure integrity. This article describes the development of a physical test method (dye ingress) for the evaluation of container-closure integrity. FD&C Red No. 40 dye was used in dye ingress studies. The dye solution visual detection limit was similar to the spectophotometric detection limit. This limit was approximately 0.0025 microL of dye/mL, which corresponds to an absorbance of approximately 0.002 absorbance units at 506 nm. Breached vials with various sizes of microtubes were utilized to correlate the dye ingress method with a microbial ingress method. The inner diameter of the microtubes ranged from 2 to 75 microns. The dye ingress and microbial ingress methods had similar sensitivity to breached vials. One advantage of the dye method over microbial ingress is that it may be utilized with vials containing formulations that are cidal or static to microbes. Thus, the dye ingress method is considered an excellent test method for evaluating container-closure integrity.

5. Introduction to Laser-Based Headspace Inspection and the Application to 100% Container Closure Inspection of Sterile Pharmaceutical Containers D.I. Duncan and J.R. Veale http://www.lighthouseinstruments.com/uploads/New_documents_9Jan2015/....pdf ABSTRACT Laser-based headspace inspection is a method used for the inspection of finished sterile product. Quantifying the physical conditions in the headspace of sterile containers enables the monitoring of critical quality parameters and gives detailed insight into the process. Container closure integrity in particular can be monitored rapidly and non-destructively by headspace gas analysis. Changes in the headspace gas pressure or gas composition are leak indicators for sterile product packaged under modified atmosphere conditions. For containers stoppered under vacuum, a leak causes a rise in headspace pressure towards atmospheric levels. For containers stoppered at or near atmospheric pressure of an inert gas and exposed to air, a leak causes oxygen ingress into the headspace. The leak rates that result in pressure rise or oxygen ingress are dependent on container volume and pressure differential for a given hole size. In general the head- space pressure and oxygen concentration of small volume parenterals (e.g. 2-10mL) packaged under vacuum rise more quickly than the headspace pressure and oxygen concentration of large volume parenterals pack- aged near atmosphere. Detectable changes in the headspace conditions of a gross leaker occur within min- utes. A micro-leak (< 1 micron) will exhibit detectable changes in the headspace after a few hours to a few days depending on the initial headspace conditions. Automated laser-based headspace inspections systems are now implemented and validated for 100% container closure inspection of sterile pharmaceutical containers at production speeds. Such implementations give insight into the process, ensure the maintenance of sterility for finished product after capping, and can be seen as a tool for meeting current regulatory guidance.

6. Application of fluid modeling to determine threshold leak size for liquid foods. Keller S1, Marcy J, Blakistone B, Hackney C, Carter WH, Lacy G. http://www.ncbi.nlm.nih.gov/pubmed/12870762 Abstract In this study, the mechanism by which a package defect converts to a leaker was examined in an effort to develop a relationship between threshold leak size and loss of package sterility. The threshold leak size is the hole size at which the onset of leakage occurs. The threshold pressure is the pressure required to initiate a leak. Leak initiation was studied in terms of the interaction between three components: liquid attributes of liquid food products, defect size, and pressures required to initiate liquid flow. Liquid surface tension, viscosity, and density values were obtained for 16 liquids. The imposed pressures required to initiate flow through microtubes with interior diameters of 0, 2, 5, 7, 10, 20, and 50 microm were measured with the use of 63 test cells filled with safranin red dye, tryptic soy broth, and distilled water with surface tensions of 18.69, 44.09, and 64.67 mN/m, respectively. Significant differences (P<0.05) between threshold pressures observed for safranin red dye, tryptic soy broth, and distilled water were found. Liquids with low surface tensions, such as safranin red dye, required significantly lower threshold imposed pressures than did liquids with high surface tensions, such as distilled water (P<0.05). An equation to quantify the relationship between liquid surface tension, threshold imposed pressure, and defect size was developed. Threshold pressures observed were not significantly different (P>0.05) from those predicted by the equation. Imposed pressures and vacuums generated within packages during random vibration and sweep resonance tests were measured for brick-style aseptic packages (250 ml), metal cans (76.2 by 114.3 mm [425 ml]), 1-qt gable-top packages (946 ml), 0.5-gal gable-top packages (1.89 liters), and 1-gal milk jugs (4.25 liters). Significant differences between packages were found with respect to observed generated pressures during vibration testing (P<0.05). An equation to calculate threshold size on the basis of liquid surface tension and imposed pressure was established.

7. Bioaerosol Exposure Method for Package Integrity Testing Scott W. Keller, Joseph e. Marcy, Barbara A. Blakistone, Walter H. Carter https://www.researchgate.net/publication/233598611_... Abstract Test organism motility, concentration, aerosol exposure time, hole diameter and length were evaluated to determine their influence on microbial ingress into a flexible plastic pouch. Microtubes with 10- and 20-μm hole diameters and of 5- and 10-mm lengths were used as defects in 128 flexible pouches. A bioaerosol with a 2.68-μm mean particle size comprised of 102 or 106 CFU/ml source concentrations of motile or nonmotile Pseudomonas fragi TM 849 was introduced into a 119,911-cm3 chamber for exposures of 15 or 30 minutes. Six pouches showed test organism growth after a 72-h incubation period. Microbial ingress was significant (P < .05) for motile test organisms with source concentrations of 106 CFU/ml.

8. Pharmaceutical container/closure integrity. VI: A report on the utility of liquid tracer methods for evaluating the microbial barrier properties of pharmaceutical packaging. Kirsch LE PDA J Pharm Sci Technol. Abstract The relationship between a liquid tracer package leak test (Mg ion ingress) and microbial immersion challenge test was demonstrated by direct and indirect correlation techniques. Rubber-stoppered glass vials with micropipette leaks were evaluated by a helium leak rate method, filled with broth, sterilized, and immersed in a bath containing microorganisms (E. coli/B. diminuta) and liquid tracer (Mg ions). After exposure and incubation, each unit was evaluated for liquid tracer ingress by atomic absorption spectrophotometry and for microbial ingress by visual inspection and blood agar streaking. Two hundred and eighty sterile broth-filled test units were challenged with microorganisms and liquid tracer. One hundred and fourteen units showed neither liquid tracer nor microbial ingress. One hundred and eight units were positive for both microbial and liquid tracer ingress. No test units were positive for microbial ingress but not for liquid tracer ingress. Fifty-eight units were positive for liquid tracer ingress but failed to show microbial ingress. Logistical regression was used to demonstrate that the probability of liquid tracer ingress was greater than microbial ingress at all leak sizes. The results indicate that the liquid tracer method studied herein was a useful indicator of the microbial barrier properties of pharmaceutical packaging. Additionally, the results support the contention that liquid penetration of a leak is required for microbial ingress.

9. The pharmaceutical vial capping process: Container closure systems, capping equipment, regulatory framework, and seal quality tests. Mathaes R, Mahler HC, Buettiker JP, Roehl H, Lam P, Brown H, Luemkemann J, Adler M, Huwyler J, Streubel A, Mohl S. http://www.ncbi.nlm.nih.gov/pubmed/26654992 Abstract Parenteral drug products are protected by appropriate primary packaging to protect against environmental factors, including potential microbial contamination during shelf life duration. The most commonly used CCS configuration for parenteral drug products is the glass vial, sealed with a rubber stopper and an aluminum crimp cap. In combination with an adequately designed and controlled aseptic fill/finish processes, a well-designed and characterized capping process is indispensable to ensure product quality and integrity and to minimize rejections during the manufacturing process. In this review, the health authority requirements and expectations related to container closure system quality and container closure integrity are summarized. The pharmaceutical vial, the rubber stopper, and the crimp cap are described. Different capping techniques are critically compared: The most common capping equipment with a rotating capping plate produces the lowest amount of particle. The strength and challenges of methods to control the capping process are discussed. The residual seal force method can characterize the capping process independent of the used capping equipment or CCS. We analyze the root causes of several cosmetic defects associated with the vial capping process.

10. Leak testing in parenteral packaging: establishment of direct correlation between helium leak rate measurements and microbial ingress for two different leak types. Morrical BD, Goverde M, Grausse J, Gerwig T, Vorgrimler L, Morgen R, Büttiker JP. PDA J Pharm Sci Technol. Abstract A direct test method using helium leak detection was developed to determine microbial ingress in parenteral vial/rubber closure systems. The purpose of this study was to establish a direct correlation between the helium leak rate and the presence of ingress when vials were submersed under pressure in a broth of bacteria. Results were obtained for two different types of leaks: microholes that have been laser-drilled into thin metal plates, and thin copper wire that was placed between the rubber closure and the glass vial's sealing surface. The results from the microholes showed that the helium leak rate was a function of the square of the hole diameter and fit well with theoretical calculations. The relationship with the wire gave a far more complex dependence and was not modeled theoretically. Comparison with the microbial challenge showed that for microholes a lower size limit was found to be 2 microm with a corresponding leak rate of 1.4 x 10(-3) mbarl/s. For the fine wire experiment the lower limit was 15-microm wire and a corresponding leak rate of 1.3 x 10(-5) mbarl/s. From these tests a safe, lower limit, leak rate was established.

11. Evaluation of Container Closure System Integrity for Storage of Frozen Drug Products: Impact of Capping Force and Transportation Nieto A, Roehl H, Adler M, et al. PDA J Pharm Sci and Tech 2018, 72 544-552 https://www.ncbi.nlm.nih.gov/pubmed/29853608 Abstract: Frozen-state storage and cold-chain transport are key operations in the development and commercialization of biopharmaceuticals. Today, several marketed drug products are stored (and/or shipped) under frozen conditions to ensure sufficient stability, particularly for live viral vaccines. When these products are stored in glass vials with stoppers, the elastomer of the stopper needs to be flexible enough to seal the vial at the target’s lowest temperature to ensure container closure integrity and thus both sterility and safety of the drug product. The container closure integrity assessment in the frozen state (e.g., _20°C, _80°C) should include container closure integrity (CCI) of the container closure system (CCS) itself, impact of processing (e.g., capping process on CCI), and impact of shipment and movement on CCI in the frozen state. The objective of this work was to evaluate the impact of processing and shipment on CCI of a CCS in the frozen state. The impact on other quality attributes was not investigated. In this light, the ThermCCI method was applied to evaluate the impact of shipping stress and variable capping force on CCI of frozen vials and to evaluate the temperature limits of rubber stoppers. In conclusion, retaining CCI during cold storage is mostly a function of vial–stopper combination, and temperatures below _40°C may pose a risk to the CCI of a frozen drug product. Variable capping force may have an influence on the CCI of a frozen drug product if not appropriately assessed. Regarding the impact of shipment on the CCI of glass vials, no indication was given at room temperature, _20°C, or _75°C when compared with static storage at such temperatures.

12. Quantifying the Vial Capping Process: Residual Seal Force and Container Closure Integrity Ovadia R, Streubel A, Webb-Vargus Y, et al. PDA Journal of Pharmaceutical Science and Technology, 2018 https://www.ncbi.nlm.nih.gov/pubmed/29954924 Abstract: Capping completes the closure of parenteral drug products in the final packaging container and is critical in maintaining an integral seal to ensure product quality. Residual seal force (RSF) is considered the sole quantifiable attribute for measuring seal “goodness” and potentially enables non-subjective, consistent setting of cappers across manufacturing sites. However, the consistency and reliability of RSF measurement and data have been scarcely reported, and the relationship between RSF and container closure integrity (CCI) remains poorly understood. Here, we present a large data set generated from a commercial capper and the results from a laboratory capper of glass vials and rubber stoppers with aluminum caps. All RSF values exhibited significant variability. We evaluated four potential sources of variability: the capper, the RSF Tester, the time dependent nature of RSF, and the components. We determined that the capper, the Tester, and the time dependent nature are not main sources. Dimensional tolerances of the packaging components were the root cause for the container closure system (CCS) configurations tested in this study. This study correlated RSF with CCI (via helium leakage) although CCI is not sensitive to RSF; CCI was maintained even for loosely capped vials with no measurable RSF. This was attributed to the stopper’s two sealing surfaces: the valve seal and the land seal. A methodology capable of differentiating the two seals’ functions demonstrated that vials with only the valve seal always passed leakage testing for a selected CCS configuration in this study, while vials with only the land seal failed CCI at low RSF values. This observation allows proposal of a low RSF limit that is safe even when the valve seal is defective. Simplified statistical analysis of commercial capping data, with the input of sample size, allowed the relationship between RSF’s low limit and an allowable failing rate to be established. Overall, despite the inherent variability of RSF, this study shows that it is a feasible parameter for capping process quantification, and demonstrates the potential of RSF measurement in capper setup.

13. Holistic Considerations in Optimizing a Sterile Product Package to Ensure Container Closure Integrity Degrazio FL PDA J Pharm Sci and Tech 2018, 72 15-34 https://www.ncbi.nlm.nih.gov/pubmed/29030527 Abstract: A new major chapter dealing with container closure integrity was released by the United States Pharmacopeial Convention. Chapter _1207_ provides a significant amount of education and guidance concerning test methodologies to prove that a system is integral and safe for use. The test method used is only one of the major considerations in approaching the challenge of proving an integral system. This paper takes a holistic review of all the major considerations needed in qualifying a new vial system for container closure integrity. There is substantial interplay among many aspects in the process of sealing a vial. This review helps to define major risks that need to be considered and mitigated and reinforces the need to understand the maximum allowable leakage limit that is acceptable for a specific drug application. A typical risk-based approach considers materials, test methods, process, people, environment, and equipment. Each of these aspects is considered in some detail along with a recommended process flow for building a best practice, science-based approach. This approach will inform decision making for evaluating the correct combination of components and assuring they are assembled and tested in an appropriate manner. This work, once completed, can be the basis for a vial system platform or specific drug application qualification.

14. Method Development for Container Closure Integrity Evaluation via Headspace Gas Ingress by Using Frequency Modulation Spectroscopy Victor KG, Levac L, Timmins M, et al. PDA J Pharm Sci and Tech 2017, 71 429-453 https://www.ncbi.nlm.nih.gov/pubmed/28733333 Abstract: USP _1207.1_ Section 3.5 states that “A deterministic leak test method having the ability to detect leaks at the product’s maximum allowable leakage limit is preferred when establishing the inherent integrity of a container-closure system.” Ideally, container closure integrity of parenteral packaging would be evaluated by measuring a physical property that is sensitive to the presence of any package defect that breaches package integrity by increasing its leakage above its maximum allowable leakage limit. The primary goals of the work presented herein were to demonstrate the viability of the nondestructive, deterministic method known as laser-based gas headspace analysis for evaluating container closure integrity and to provide a physical model for predicting leak rates for a variety of container volumes, headspace conditions, and defect sizes. The results demonstrate that laser-based headspace analysis provides sensitive, accurate, and reproducible measurements of the gas ingress into glass vial-stopper package assemblies that are under either diffusive or effusive leak conditions. Two different types of positive controls were examined. First, laser-drilled micro-holes in thin metal disks that were crimped on top of 15R glass vials served as positive controls with a well-characterized defect geometry. For these, a strong correlation was observed between the measured ingress parameter and the size of the defect for both diffusive and effusive conditions. Second, laser-drilled holes in the wall of glass vials served as controls that more closely simulate real-world defects. Due to their complex defect geometries, their diffusive and effusive ingress parameters did not necessarily correlate; this is an important observation that has significant implications for standardizing the characterization of container defects. Regardless, laser-based headspace analysis could readily differentiate positive and negative controls for all leak conditions, and the results provide a guide for method development of container closure integrity tests.

15. Container Closure Integrity Testing—Practical Aspects and Approaches in the Pharmaceutical Industry Brown H, Mahler HC, Mellman J, et al. PDA J Pharm Sci and Tech 2017, 71 147-162 https://www.ncbi.nlm.nih.gov/pubmed/27789803 Abstract: The assurance of sterility of a parenteral drug product, prior to any human use, is a regulatory requirement. Hence, all strategies related to container closure integrity (CCI) must demonstrate absence of microbial contamination through leaks as part of the container closure system (CCS) qualification, during manufacturing, for quality control purposes and to ensure microbiological integrity (sterility) during storage and shipment up to the end of product shelf life. Current regulatory guidances, which differ between countries and regions, provide limited detail on how to assess CCI. The new revision of USP _1207_ aims to provide extensive and detailed guidance for CCI assessments for sterile products. However, practical questions and considerations are yet to be addressed by the pharmaceutical industry. These may include: (1) choice of method, for example whether a deterministic CCI method (e.g., helium leak) is preferable over the probabilistic CCI method (e.g., microbial ingress), (2) the type of primary packaging (e.g., vial, syringe, device), (3) dosage form (e.g., liquid versus lyophilisate), (4) suitable acceptance criteria, (5) appropriate sample size, (6) the most appropriate way to introduce artificial leaks into the CCS, (7) ensuring suitable assurance of CCI during drug product manufacturing, and (8) evaluating CCI under intended shipment and storage conditions (e.g., in the frozen state). A group of European industry peers have met to discuss these and other related questions in order to provide their viewpoint and best practice on practical approaches to CCI. Their perspective is provided in this white paper. Through these discussions, it became clear that there is currently no gold standard for CCI test methods or for the generation of artificial leaks; therefore flexibility toward CCI approaches is required. Although there should be flexibility, any CCI approach must consider the intended use (e.g., CCS qualification, routine manufacturing, or quality control) and product design (e.g., primary packaging, liquid versus dried product).

16. Artificial Leaks in Container Closure Integrity Testing: Nonlinear Finite Element Simulation of Aperture Size Originated by a Copper Wire Sandwiched between the Stopper and the Glass Vial Nieto A, Roehl H, Brown H, et al. PDA J Pharm Sci and Tech 2016, 70 313-324 https://www.ncbi.nlm.nih.gov/pubmed/27020649 Abstract: Container closure integrity (CCI) testing is required by different regulatory authorities in order to provide assurance of tightness of the container closure system against possible contamination, for example, by microorganisms. Microbial ingress CCI testing is performed by incubation of the container closure system with microorganisms under specified testing conditions. Physical CCI uses surrogate endpoints, such as coloration by dye solution ingress or gas flow (helium leakage testing). In order to correlate microbial CCI and physical CCI test methods and to evaluate the methods’ capability to detect a given leak, artificial leaks are being introduced into the container closure system in a variety of different ways. In our study, artificial leaks were generated using inserted copper wires between the glass vial opening and rubber stopper. However, the insertion of copper wires introduces leaks of unknown size and shape. With nonlinear finite element simulations, the aperture size between the rubber stopper and the glass vial was calculated, depending on wire diameter and capping force. The dependency of the aperture size on the copper wire diameter was quadratic. With the data obtained, we were able to calculate the leak size and model leak shape. Our results suggest that the size as well as the shape of the artificial leaks should be taken into account when evaluating critical leak sizes, as flow rate does not, independently, correlate to hole size. Capping force also affected leak size. An increase in the capping force from 30 to 70 N resulted in a reduction of the aperture (leak size) by approximately 50% for all wire diameters. From 30 to 50 N, the reduction was approximately 33%.