An acoustical panel includes an acoustical layer having an interlocking
matrix of calcium sulfate dihydrate, polyethylene glycol and at least one
of the group fibers, a lightweight aggregate and mixtures thereof. The
acoustical layer has voids in the interlocking matrix that are configured
to absorb sound. The polyethylene glycol is selected to agglomerate dust
at temperatures generated by friction when the panel is cut. A method of
making the acoustical panel includes making a slurry comprising calcium
sulfate hemihydrate, polyethylene glycol, water and at least one of the
group consisting of a lightweight aggregate, fibers and combinations
thereof. Foam is added to the slurry, preferably at the mixer discharge.
A continuous strip of acoustical layer material is formed from the
slurry. The acoustical panels are formed by cutting the strip into
individual panels. Finally, the partially hydrated calcium sulfate
hemihydrate is allowed to fully set.