Because the physical condition of a building can change greatly over time due to external forces such as sun, wind and rain, choosing materials that will maximize the life and appearance of the structure, while minimizing the amount of damage, is crucial. This is especially true in selecting a sealant. Following are some of the most common aesthetic issues to consider.

• Dirt Pick-Up – Accumulation of dirt on a sealant’s surface is particularly prevalent on construction sites with large amounts of dust. The actual amount of dirt pick-up will vary with exposure conditions, but excessive pollutant contamination will result in lower durability and weaker bond strength. To avoid this, choose a sealant that can tolerate higher levels of contamination.
• Chalking – As the substrate begins to degrade and erode over time, the surface becomes more rough and porous, which leads to a loss of surface gloss and color. Chalking is most observed in organic sealants that are initially black or brown, but later transform into a light gray or beige. This does not occur with silicone or acrylic sealants.
• Change of Color – Color change can result from factors both inherent and external to the sealant. Incompatibility of the sealant with other building materials is a contributing factor. Materials with high incompatibility levels include low-molecular-weight polymers, antioxidants or tar. A sealant that is compatible with a variety of other substrates is preferable.
• Surface Crazing – A variety of factors, including sunlight, environmental stress and aging, can cause cracks in the sealant’s surface. This is especially common with organic sealants. Generally, sealants with higher polymer content are more durable and less subject to crazing.
• Fluid Migration – Fluids can migrate from a sealant to the substrate, creating a dark “wet” band look around the joint of the sealant. The extent and rate of fluid migration varies with the type of sealant. Cheaper, less formulated sealants are the most prone to staining and fluid migration.
• Other Environmental Factors – Oxygen, ultraviolet radiation, climate/temperature, microbial growth and other environmentally-induced mechanisms can contribute to the fatigue and stress that degrades and lowers the overall bond strength of the sealant.

While aesthetic issues cannot be completely avoided, they can be mitigated through prior knowledge; selection of high-quality, high- performance building materials; and working with a reputable manufacturer.

About Dow Corning Construction

For more than 60 years, Dow Corning has provided silicon-based, performance-enhancing materials and additives for glazing, sealing, and weatherproofing new and existing construction projects. For more information, visit www.dowcorning.com/construction.

Links

• Dow Corning