Heat welding of flexible plastics is a way of creating a physical molecular bond between two materials which are melted and pressed together until they cool and bond. The technique has been used widely for bonding vinyl and other similar materials in everything from advertising banners to truck sides and even roofing materials. It has also been used for many years to manufacture dry bags and works particularly well with PVC. The weld created by heat welding is typically fairly wide compared to the more precise high frequency welding technique and is often achieved by either a hot air gun or heated rollers sometimes built into what looks like a very large sewing machine. Where similar materials are used the bond is extremely strong and will be resistant to being pulled apart. The technique of heat welding is used in Aquapac's heavyweight dry bags and duffels where you can see in the pictures that the weld is fairly thick (about a centimetre wide) as opposed to the 2 mm wide weld which we are able to achieve using high frequency welding