Glass bubbles* have been used for decades in construction, paint, and coatings applications to provide both application and performance benefits such as lightweighting, viscosity control, improved shrink and crack resistance in thick films, and thermal insulation. Thermal insulation is accomplished via the hollow structure of the glass bubbles, and the fact that they contain air, which provides more pore volume. There are many grades and chemistries available for glass bubbles. 3M offers true soda-lime borosilicate hollow glass bubbles that are specified by a strength/density relationship. Higher strength equates to a thicker shell, thus producing a higher density and a higher thermal conductivity due to less void space content. Conversely, the lower density glass bubbles offer more void space due to the larger particle size. This, in turn, yields lower thermal conductivity values, which can result in improved thermal insulation properties. Table 11 shows a condensed list of select 3M™ Glass Bubbles and their corresponding thermal conductivity values for the bubbles only.