failure. With some plastic films, observation can be enhanced by using polarized light which highlights the birefringence of the heat seal. Some seals for sensitive products require thorough verification and validation protocols that use quantitative testing. Test methods might include: Seal Strength per ASTM F88 and F2824 Seal Strength testing, also known as Peel Testing, measures the strength of seals within flexible barrier materials. This measurement can then be used to determine consistency within the seal, as well as evaluation of the opening force of the package system. Seal strength is a quantitative measure for use in process validation, process control and capability. Seal strength is not only relevant to opening force and package integrity, but to measuring the packaging processes’ ability to produce consistent seals. Burst and Creep per ASTM F1140 and F2054 The burst test is used to determine the packages strength and precession. The burst test is performed by pressurizing the package until it bursts. The results for the burst test include the burst pressure data and a description of where the seal failure occurred. This test method covers the burst test as defined in ASTM F1140. The Creep test determines the packages ability to hold pressure for an extended period. The creep test is performed by setting the pressure at about 80% of the minimum burst pressure of a previous burst test. The time to seal failure or a pre-set time is measured. Vacuum Dye per ASTM D3078 Determination of package integrity. The package is submerged in a transparent container filled with a mixture of water and dye. Vacuum is created inside the container and maintained for a specific length of time. When the vacuum is released, any punctured packages will draw in dye revealing the imperfect seal. See also Hermetic seal Plastic bag Plastic welding Shrink wrap Tensile testing Waxtite References General references Selke, S,. "Plastics Packaging", 2004, Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002, Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, Crawford, Lance, "Port Sealing: An Effective Heat Sealing Solution". Plastic Decorating Magazine. January/February 2013 Edition. . (Topeka, KS: Peterson Publications, Inc.). Section: Assembly: pages 36–39, covers Crawford's article. ASTM D3078 – Standard Test Method for Determination of Leaks in Flexible Packaging by Bubble Emission ASTM F88 – Test Method for Seal Strength of Flexible Barrier Materials ASTM F1140 - Standard Test Methods for Internal Pressurization Failure Resistance