Developments in chemistry, materials and manufacturing have truly revolutionised the building of kayaks.
In the past, kayaks were created individually. Composites and production moulds allowed manufacturers to turn kayaks into mass-market items.
One of the most important criterions about the quality of a modern kayak is its hull’s strength that manifests itself in the ability of a boat to keep its shape intact under stress and not crack or split.
The toughness of the hull is important because a kayak needs to be able to withstand sandpaper-like shores and landings and dings of day-to-day operation.
A lot of newbies seem to be overly concerned about the weight of kayaks, not realising that the bare hull of a kayak typically accounts for less than 25% of the total weight of the boat. The remaining 75% comes from parts such as seats, hardware, hatches and various devices that you may want to use when touring on a kayak.
Even with all these parts and devices, the weight of your body is most likely two to three times larger than the weight of your kayak.
Unless you are a professional racer, you should not obsess about the weight and lightness of your kayak. You can do so, but you will have to pay for it. Both directly when it comes to price of a boat and metaphorically when it comes to the level and amount of maintenance you will have to do on an expensive boat. If you do have money to spend, you will be better off getting a high-end high-quality paddle.
Most modern sea kayaks made of composite materials have a layer of resin on the outside of the hull. This layer is known as gel coat. Its function is to protect the boat against abrasion of the sand and against the rays of the sun.