Seam Leakage Test

Whether water passes through the seam assemblies we build, and how the answer changes between a plain seam, a seam with a sealed or taped construction, and a seam reinforced or overlapped for a load bearing position such as a shoulder. Test method: to be confirmed with the laboratory, applied identically to every specimen. Conditions required for a comparison to mean anything: the fabric and membrane specification; the seam type, thread, stitch density and seam allowance; whether and how the seam is taped or sealed, and the tape width and application method; the seam position sampled, because a straight side seam, a curved shoulder seam and a lapped seam behave differently; how the specimen is mounted and how its outer edges are sealed against bypass leakage; the pressure and duration of the test; the ambient conditions; and the number of specimens per seam construction. Where the seam construction is not identical, the comparison is between constructions rather than between fabrics.

The buyer who asks for a waterproof fabric almost never asks for a waterproof seam, and the seam is where the garment leaks. Specifying and sealing seams is one of the most expensive construction decisions in a cold weather shell: it adds tape, labour, a dedicated machine and an inspection step, and it is also the first item removed when a quotation has to be made cheaper. Because a leaking seam appears only in use, the buyer discovers the saving in the field, at which point the whole delivery is suspect. A comparison under one method gives the buyer a way to see what the sealing step actually delivers, and a way to defend the cost of it in a tender.