Waterproof sprays are chemical products, typically in aerosol or pump form, applied to the surface of various materials. They create a temporary barrier that repels water from items like clothing, footwear, and outdoor equipment. Their primary function is to restore or enhance a material’s ability to shed water, protecting the underlying surface from absorbing moisture. These treatments are a popular method for extending the life and function of gear exposed to the elements.
Understanding How Waterproof Sprays Create Barriers
Waterproof sprays function by imparting a hydrophobic quality to the material’s surface, meaning the surface actively resists water molecules. This effect is achieved through specific chemical compounds dissolved in a solvent that evaporates after application. The resulting chemical layer coats the individual fibers or surface structure rather than sealing the material completely.
Common active ingredients include silicone, acrylic polymers, and fluorochemicals, sometimes referred to as per- or poly-fluoroalkyl substances (PFAS). These compounds have a low surface energy, which prevents water from spreading out and wetting the material. When a water droplet hits the treated surface, the cohesive forces holding the water molecules together become stronger than the adhesive forces trying to bond the water to the material. This molecular imbalance causes the water to bead up into nearly spherical droplets and roll off instead of soaking in.
This process is scientifically known as creating a high contact angle between the water and the surface. When the spray is applied, it leaves behind a non-polar layer that minimizes the physical contact area between the liquid and the material. The surface tension of the water itself is leveraged to keep the droplet intact and mobile. Therefore, the spray does not make the item truly waterproof, but rather imparts a durable water repellent (DWR) finish.
Effectiveness Varies by Material Type
The degree to which a waterproof spray is effective is heavily dependent on the material it is applied to, rather than being a universal solution. Sprays perform differently on materials with varying degrees of porosity and weave tightness. Porous materials, such as suede, unfinished leather, and canvas, generally benefit the most from the treatment because they are naturally absorbent.
For materials like suede and nubuck, the spray seals the tiny pores and fibers to block capillary action that would otherwise pull water deep into the material. This offers a high degree of protection, though the softer texture of the material can be slightly altered by some formulas. Tightly woven synthetics like nylon and polyester, especially those already treated with a factory DWR finish, already possess a low level of absorbency. The spray simply refreshes this existing non-absorbent layer.
Finished leather, which is less porous than suede, or materials with complex membranes like some outdoor jackets, require specific formulas to avoid clogging or residue buildup. Silicone-based sprays, for instance, can compromise the breathability of technical fabrics by filling the microscopic pores designed to allow moisture vapor out. Selecting a spray formulated for the specific material is necessary to achieve the intended result without damaging the item’s properties. The spray only affects the outer layer, meaning it cannot make a non-sealed seam or zipper waterproof.
Maximizing Application and Durability
The longevity and performance of a waterproof spray are largely determined by the application technique and the ongoing maintenance of the treated item. For the best results, the surface must be thoroughly cleaned and completely dry before the spray is applied. Dirt, oils, and other residues will prevent the active ingredients from properly bonding to the material’s fibers, leading to an uneven and short-lived barrier.
Application should be performed in a well-ventilated area, holding the can a specific distance away (typically six to eight inches) to ensure a fine, even mist. Applying multiple thin coats, allowing for a short drying time between each, is more effective than a single heavy coat. Once the final coat is applied, the item usually requires a curing time, sometimes up to 24 hours or with the use of low heat, to allow the polymers to fully set and create the maximum bond.
The effectiveness of the DWR finish will inevitably degrade over time due to several factors related to use and wear. Abrasion from simply wearing the item, frequent washing with standard detergents, and exposure to UV light will all break down the chemical coating. For items like shoes worn daily in wet conditions, reapplication may be necessary every few weeks. For less frequently used items, such as tents or seasonal jackets, the effect can last for several months.