We’ve seen them at bars, restaurants and private parties — those everyday essentials to protect tabletops from spills and condensation. We’re talking about the ubiquitous coaster.

Sometimes coasters are paper bedecked with the logo of a favorite brew, an advertisement or a political candidate. On more formal occasions, they could be crystal, but their purpose is the same — shielding potentially damageable surfaces from moisture and permanent scarring due either to careless spills or normal condensation. Coasters also help to protect surfaces from heat damage if coffee, tea and other warm beverages are atop.

But who knew how expansive this quirky tegestology could be. (That’s the science of coaster collecting.) While most tegestologists specialize in beer mats from around the world, others collect a wide variety of beverage coasters.

Looking back

Coasters began as simple pieces of fabric used to not only protect wooden bar surfaces but also to keep dirt and insects out of beverages. In the late 1800s, the first commercially produced pressed-paper custom coasters were made by a German printing company named Friedrich Horn. Fast forward to today, and while the original protection function remains, there are literally thousands of types of coasters available.

Material pleasures

Coasters should absorb water without allowing it to pass onto the surface below. Some do, while others form a barrier but may not actually be absorbent.

When selecting coasters, you’ll find myriad options to choose from — paper, cardboard, sandstone, tile, wood, metal, cork, beads, glass, fabric, paper, leather, bamboo, silicone, agate, plastic, mirrors, resin, terracotta, slate, crystal and more.

Some coasters are dimensional with rims or borders for drink stability, while others may stand an inch or so deep with recessions to fit specific drinkware or a wine bottle and cork.

Most coasters have a backing to protect the table surface from scratching or other damage from the uppermost material. Look for felt or cork backings and often thin “bumper” pads to slightly elevate the coaster from the surface. Other coasters actually have legs.

Many coasters come in sets, often with holders to corral the grouping. The coasters may all be the same or related by theme.

Shape smart

Coasters come in many shapes, but the two most common are round and square. Usually 4 to 6 inches across, they’ll span the diameter of most cans, bottles or glasses. Those coasters designed for specific glassware or bottles may be slightly larger.

Novelty coasters can be shaped like leaves, puzzle pieces, clouds, cartoon characters, etc. Some metal coasters are actually shaped like people, mangled silverware and racetracks.

Theme trends

Coasters can be found in almost every theme imaginable. Common subjects include framed art, historical paintings, nature, sports, movie stars, superheroes, monograms, quotations and trivia, comics, landmarks, food, graffiti and toys.

There are coasters that look like Oreo cookies, chocolate squares, hamburger components, sandwiches, toast and a host of other food options.

Since people often write notes and business proposals on coasters and cocktail napkins, there are even coasters with notebook-paper blue rules and yellow legal pads. And don’t forget the take-home coasters with drink recipes printed on them for your future imbibing.

For the technology lovers, look for coasters mimicking a floppy disk, CD, math symbols or chemical elements. There are also coasters depicting iPhone icons. One company offers coasters made of real shredded currency.

Other novelty options include cause-related table protectors, like those designed by the Mumbai Traffic Police that show photos of people, and when a drink is placed on them, a special previously invisible blood-red ink appears as an instant reminder of the hazards of drunken driving. There are also coasters in the shape of pink ribbons to raise breast cancer awareness. A group called Drink Safe Texas has developed coasters that can detect date-rape drugs from a simple splash of the drink above.

Some coasters made from slate or covered with chalkboard paint allow the drink owner to write his or her name on the protector to avoid any mix-up in similar-looking drinks.

Not all coasters sit passively under a drink; some are interactive. There are several games available, like Rubik’s Cube and Scrabble, movable Legos and a set of DIY coaster frames to fill with your favorite wine corks (after use, of course).

Several companies offer pressure-activated coasters. Philips Lumiware coasters change colors, illuminating the drink placed on them. With LED lights, they are wirelessly rechargeable and glow for about 12 hours—long enough to entertain even lingering party guests.

For the scientific-minded, there are coasters depicting the radioactive elements that glow eerily when a drink is placed on them.

Kids might love coasters that look rather mundane, but when a warm beverage like cocoa is placed on them, a design is revealed. Or perhaps they’d prefer clear resin coasters with various colorful candy favorites embedded.

If you’d like to give the bar a piece of your mind, look for coasters printed with surveys about the service and food — just fill in the blanks.

To fool your neat-nick drinking friends, look for Clumsy Coasters that look like a clear water spill. If your guests are really all thumbs, look for coasters that fit around the bottom of a glass and stay with it no matter where the glass goes.

Eco-minded drinkers will appreciate Molson Canadian’s paper coasters with integrated seeds. After use, they can be planted and watered to grow into black spruce trees.

Personalizing coasters

Should you not be able to find coasters that fit your taste, it’s easy to personalize your own. Several companies will print your custom image, photo or special-occasion message on coasters. The latter is popular for weddings and baby showers.

Some coasters are multilevel, offering a photo frame surface and space below to slip in a favorite pic.

If you’re the least bit crafty, it’s easy to make your own coasters. The important thing to aim for is a flat, level surface to avoid tipping drinks. Use an absorbent material.

Close cousin

Quilters have expanded on the coaster concept to create what’s called mug rugs. A mug rug is like a miniplacemat — large enough for a coffee cup and perhaps a pastry, wine and crackers, or cookies and milk. These little fabric quilts are usually about 4-by-6 inches up to 6-by-10 inches.

Mug rugs, like coasters, are designed to protect the surface from heat and moisture but offer a little more room so your morning treat doesn’t have to sit right on the desktop.

So, whether you become a coaster collector or just like to amuse yourself at restaurants by noting all of the various options available, know that you can indeed finalize business deals, make notes or pass your phone number to someone on those mini table protectors.

— Reporter: gwizdesigns@aol.com