Why Does Glass Interlayer Yellow?

Yellowing

• One complaint of using laminate glass is its yellowish tint caused by a UV inhibitor. This tint is not something that happens with time, but is the result of a cheaper polyester interlayer. The strength of the yellow tint depends on how thick the interlayer is; the thicker the layer, the more noticeable the yellow color. In spite of the coloring, polyester is often used because it is cheaper and does not require the extra work and specialized equipment of higher-quality polyurethane resins.

Other Colors

• One advantage of laminating with polyester resin is that it can be mixed with any color for a custom tint. This disguises the yellow tinting. Custom colors are easily created to match any environment or structure. Polyurethane resins do not take color as well, but the resin itself is much clearer than polyester.

Wet and Dry

• Polyester resins are sometimes limited to dry applications, because without proper edge sealing, water can damage the laminate. Polyurethane resins are completely impervious to water after drying and do not require an edge seal. Other materials, such as rice paper or fabrics, can be pressed into polyester resin interlayer for interesting textures, while this is not as easily accomplished with polyurethane resins. Those materials must be 100 percent free of moisture.

Thickness

• When using polyester resins, thickness is important not only because of yellowing of the glass, but also because as the resin dries, it contracts. This contraction can end up cracking the glass. Polyurethane resins are more flexible and do not pose the same threat to the surrounding glass structure.