Guide to Wetsuit seams and stitches
The difference between flatlock stitching and blindstitching is two-fold. Flatlock stitching along the seams of wetsuit panels are cheaper to produce and suffice at doing their job. The flatlock stitching holds together the panels but lets in some water through the seam and if the stitching gets knicked the whole stitching could unravel.
Blindstitching does the same job as flatlock but is much more water tight letting hardly any water through the actual join plus if the stitching gets knicked through usual wear and tear only one stitch will be unravelled and the rest of the stitching remains intact. Great!
Most wetsuits, 3/2mm steamers and thicker 5/3mm are as a standard usually glued and blindstitched making the wetsuit warmer for the surfer and more durable.
Critical seam tape is basically just a thin 0.5mm or 1mm layer of neoprene material which is placed along the seams in the most critical places or where wear and tear might be greatest. This strengthens the wetsuit along those seams.
Fluid seam welding is the latest wetsuit seam technology. A layer of non-chafing high grade, silicon-based urethane applied in liquid form to the backside of a glued and blindstitched seam completely blocking out water. So fluid seam welding is hot welded along the seam which dramatically reduces the water that can seep through the seams and gives added strength to the seam. Plus, due to its fluid flexibleness it will not reduce the wetsuit experience. Notably, wetsuits such as O’Neill’s Psycho 2 have fluid seam welding on the BOTH sides of the seam, inside and outside, along all major seams. Most other wetsuit brands have this seam weld on the inside or outside both not both.
Which is best? At the moment the best choice for warmth and strength comes from seams that are glued and blindstitched with fluid seam weld on there too. Obviously the warmer your surfing climate the less bothered you will have to be with this stuff, but if you surf in frigid to very cold water like Northern Europe or Northern California then these choices will concern you.