How Dry Bags Are Made Waterproof
What makes a dry bag completely waterproof? There are three key design features that make dry bags completely waterproof. They are:
• PVC Tarpaulin material
• Thermo or High Frequency Welded construction
• The unique roll seal mechanism
Let's look at each in turn.
PVC Tarpaulin Material PVC Tarpaulin is a bit of a modern wonder material. It's incredibly versatile with applications as broad as truck sides, tents, inflatable boats, temporary awnings and of course, waterproof bags. The unique characteristics of PVC tarpaulin make it an ideal material. However, like most things in life, not all PVC tarpaulins are created equal. The type of PVC tarpaulin used for quality waterproof bags is 500D. This refers to the thickness and density of the fibers in the material, with 500D representing a density rating of 500. Your common household tarpaulin has a density of about 100, and the scale goes up to 1000. 500D PVC tarpaulin is the perfect balance between durability and pliability. It has great tear strength meaning it won't rip, yet it's not so stiff as to be uncomfortable to carry or difficult to seal. These characteristics mean 500D PVC tarpaulin is the perfect material for waterproof bags, and it's the material used in all quality waterproof bags. It is a completely waterproof material, and its toughness prevents any small holes appearing and letting water in.
Thermo or High Frequency Welded Construction Merely stitching the material together is not going to cut it if you want a truly waterproof bag. The process of stitching creates thousands of small holes all of which compromise the ability of the bag to keep water out. To over come this in the past, a waterproof seal is often put behind the stitching to keep the water out – think a big piece of sticky tape. The problem with this approach is that these seals often peel away or crack with time, reducing the lifespan of the bag's waterproof status. To avoid this problem all together, quality waterproof bags are constructed through either thermo or high frequency welding. For thermowelding, the principle is the same as welding metals, you use heat to melt the materials together where they bond, creating a join. Instead of stitching the materials together, heat is applied to melt them together. High frequency welding works on a similar pricinple, but instead of applying heat, uses electromagnetic waves to heat and join the material. Both techniques enable the fibers to join together to create a strong, durable and most importantly, waterproof seal. By thermo or high frequency welding, the seals remain tighter and less prone to peeling or cracking later on. It is the thermo / high frequency welded seals that enhance the waterproofing on any waterproof dry bag.
Unique Roll Seal The unique roll seal is what brings the PVC tarpaulin material and themowelding together to create a totally waterproof bag. To seal a waterproof bag, or any other dry bag for that matter, you need to fold the opening over itself 3 times. By folding it firmly and tightly, the inherent friction in the PVC tarpaulin material means it grabs on itself. This creates an airtight seal, and that is the secret to making it waterproof. If air can't get in (or out), how can water? It can't. The folds must be firm, crisp and tight. If they are not firm or tight enough, there won't be enough friction to create an airtight seal, and the bag won't be waterproof. You also need to ensure the bag isn't so full that you can't fold the top over sufficient times. The great thing about an airtight seal is that if you don't expel the air inside the waterproof bag (which you do by pushing it out whilst lightly holding the first fold), it will float on water. And it can double as a comfy pillow!
So it's the three key design features of PVC tarpaulin material, thermowelded construction and the unique roll seal that all work together to make dry bags completely waterproof.