When I started out in the roofing business almost 40 years ago, selecting the right adhesive for bonding single-ply membranes was pretty easy. That was because there were basically only two types of adhesive available: “yellow glue” to bond the membrane to a substrate and “black glue” to splice the membrane to itself. In reality, either yellow or black glue would work fine to bond a membrane to a roof deck or wall. The only risk involved using the yellow glue to splice the membrane because the yellow adhesive tended to draw moisture into the seam. Traditional yellow glue also was easy to use. It could be applied in temperatures as low as 20°F, and it tended to dry quickly regardless of temperature.
Unfortunately, traditional yellow glue wasn’t necessarily all that good for the environment. The solvents used to make this adhesive tended to contain many Volatile Organic Compounds (VOCs), which in turn tended to react with sunlight to form hazardous Ozone pollution in the atmosphere. As part of efforts to reduce Ozone levels across the United States, many states and cities started to restrict allowable amounts of VOCs used in a wide variety of products, from charcoal fluid to paints, and of course, roofing adhesives. As a result of these restrictions, roofing manufacturers started to develop low-VOC alternatives to the traditional yellow glues.