Today's exposed aggregate surfaces offer beauty and durability nearly comparable to glass tile without the expense. They contain material such as colored sand granules, pebbles, colored glass and even shells to give the pool's surface its own character. Some are pleasingly rough to the touch, while others are polished smooth.

And the stone withstands pool chemicals longer than plaster. “Anytime the water touches more aggregate than plaster, you're better off,” says Kevin Kostka, who does quality control and corporate sales for Alan Smith Pool Plastering in Orange, Calif.

Exposed aggregate surfaces appeal to everyone. Designers like their richness and depth of color. Installers appreciate their durability and lack of callbacks. The consumer wins on both counts. But reserve their application for your best crews. Their application requires more skill than what is needed for plaster. It involves troweling on the material, compacting the aggregate to get a sufficient density, then rinsing or grinding off the top layer of plaster to reveal the pebbles, beads, or granules. Surface professionals generally allow only their best crews to apply these materials.

Here, experts discuss the appeal of four types of aggregate finish, along with a tip or two for proper application.

Glass bead finishes. These materials mix colored, translucent glass beads with white or pigmented plaster. Of all the choices in exposed aggregate, this finish most closely resembles glass tile. “When the sun hits it, it glows,” Kostka says.

Colors range from the more muted combinations that work in naturalistic environments to a bright, electric blue that commands instant attention. Some of these hues are extremely vibrant, more so when the sun hits, so prepare clients in advance.

The glass beads appeal to the touch as much as the eye. “The feel is what sells everybody,” Kostka explains. “It's very smooth, almost slippery, bumpy but not rough.”

Unfortunately, some clients change their tune when they see the price—approximately 50 percent higher than other aggregate finishes, almost three times as much as plaster, Kostka says.

This surface is also the most difficult to correctly apply. Because the beads sparkle so much, they're easier to distinguish individually, which means the eye will instantly detect if one area has a higher concentration of beads than the next. While hard troweling, applicators must take extra care to maintain a consistent compaction throughout, even in the tough corners where pebble applicators sometimes use a looser density.

Crews should only attempt this material after they've absolutely mastered regular pebble finishes, Kostka advises.