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<\/a><\/p>\nLeather soles are often thought to be more breathable than rubber soles. But how much moisture can actually pass through the bottom of a shoe?<\/p>\n
In a typical Goodyear-welted shoe, moisture must pass through several layers. These include the leather insole, cork filling, adhesives, and outsole.<\/p>\n
The cork filling often contains a binding material. Strong contact adhesives are also used to hold the sole parts together.<\/p>\n
These adhesives create strong bonds and help keep water out. However, they can also make it harder for moisture vapor to pass through.<\/p>\n
So, a leather outsole does not always mean the whole sole is breathable.<\/p>\n
For the bottom of a shoe, absorbing moisture may be more important than letting moisture pass through.<\/strong><\/p>\n A thick leather insole can absorb sweat from the foot. This also helps explain why many traditional welted shoes use a half sock lining.<\/p>\n A half sock lining covers the heel area but leaves much of the leather insole exposed. This allows moisture from the foot to reach the leather instead of passing through another glued layer.<\/p>\n Interestingly, the same adhesives that limit moisture movement from inside the shoe can also help stop water from entering from outside.<\/p>\n This means keeping the foot dry from sweat and keeping outside water out are two different things.<\/p>\n Whether a shoe has a leather or rubber outsole, the material alone does not tell us how well the whole shoe handles moisture.<\/p>\n One of the most debated topics in Goodyear-welted shoes is gemming failure.<\/p>\n In machine-welted shoes, a fabric rib called gemming<\/em> is glued to the bottom of the leather insole. The welt stitching passes through this rib, helping connect the upper and welt to the insole.<\/p>\n In traditional hand-welted shoes, the same type of sewing support is cut directly from a thick leather insole.<\/p>\n The difference is important. One method uses a separate fabric rib held in place by glue. The other forms the rib from the leather insole itself.<\/p>\n If the adhesive holding the gemming fails, the rib may come loose from the insole. This can make resoling more difficult and may weaken the shoe’s structure.<\/p>\n However, gemming failure does not happen to every shoe.<\/p>\n Modern adhesives have improved greatly over the years. Many offer stronger bonds and better resistance to difficult conditions.<\/p>\n Some experienced cobblers have noticed that gemming in newer shoes seems to hold better than in older ones. However, there is still little clear test data to confirm this.<\/p>\n This shows an important point: adhesive quality can affect both how long a shoe lasts and how easy it is to repair.<\/strong><\/p>\n Adhesives also help prevent unwanted sounds inside shoes.<\/p>\n When leather parts move and rub against each other, they may create squeaking noises. Good bonding can reduce this movement.<\/p>\n Some footwear adhesive systems also use hardeners to improve certain properties, such as heat resistance and long-term durability.<\/p>\n For example, HELEY supplies hardeners and other supporting chemicals alongside its footwear adhesives.<\/p>\n In these applications, the key is not just how strong the bond is at first. It is whether the bond can remain stable through years of bending, moisture, and daily wear.<\/p>\n This shows why long-term adhesive performance plays an important role in the durability of footwear.<\/p>\n Leather-to-leather bonding is often easier when the surfaces are properly prepared. Rubber can be more difficult.<\/p>\n Different types of rubber have different chemical properties. Some contain oils or other substances that can make bonding harder.<\/p>\n This is one reason why gaps sometimes appear between rubber outsoles and welts, or between rubber soles and heel blocks.<\/p>\n In shoes held together by stitching or nails, these gaps do not always mean the sole is coming off. The stitching or nails may still keep everything in place. But the gaps can affect the shoe’s appearance.<\/p>\n The answer is not always to use a stronger adhesive.<\/p>\n In many cases, surface preparation is just as important as the glue itself.<\/strong><\/p>\n Before applying adhesive, manufacturers may need to clean, sand, or treat the material surface.<\/p>\n Cleaners remove dirt, oil, and other substances that can weaken the bond. Primers help prepare certain materials so the adhesive can hold better.<\/p>\n Companies such as HELEY<\/a> provide primers, solvent-based adhesives, and water-based adhesives for different footwear materials and production needs.<\/p>\n However, neither solvent-based nor water-based adhesives are always better. Their performance depends on the formula, material, and production process.<\/p>\n A properly prepared surface with the right adhesive can often give better results than using a very strong glue on a poorly prepared surface.<\/p>\n3. Gemming Failure and the Durability of Footwear<\/h2>\n
<\/a><\/p>\n4. Why Are Rubber Soles Harder to Bond?<\/h2>\n