A coalescing additive is used in the manufacturing process for gypsum
wallboard. Such an additive increases the surface area and density of the
slurry at the paper to core interface by coalescing the foam cells away
from the paper core interface. This permits a stronger paper to core bond
to form and increases the compressive strength of the gypsum wallboard as
compared to standard wallboards made from slurries with reduced water
levels.