Wood Coasters

Protecting a finely built piece of wood furniture is as essential as creating it. Many tabletops have been marred or ruined by people setting drinks or hot dishes on them, leaving permanent marks on the finish. While removing this damage and refinishing the tabletop is often possible, that’s an extra project that none of us need. It’s better to protect the tabletop so the time can be spent building new projects.

That’s where coasters and trivets come in. Coasters protect tabletops from the condensation around cold drinks, and trivets protect them from hot dishes when serving them. While trivets are typically considerably more significant than coasters, they are similar in many ways.

Coasters can and are made of almost any material, from paper to marble. Those printed with advertising slogans are generally made of inexpensive materials, like synthetics or cork, but wood is hard to beat for a more elegant look that complements wood furnishings. Whether the wood matches the furniture or is made to contrast it, it provides a lovely accent to the table while protecting it.

Wood coasters can vary considerably in appearance, not only due to the choice of wood used in making them but also in the manufacture of the coaster. Simple coasters might be made of only one type of wood, while more elaborate ones will mix various species to produce an attractive pattern. Epoxy resin can also be mixed in with the wood, filling gaps between individual wood pieces, whether those gaps are intentionally created or due to combining the live edge of several pieces of wood.

The number of coasters being created at one time may impact design considerations. As we will see in making butcher block coasters, the decision on whether to make the coasters end grain or long grain depends mainly on how many coasters are being made. If all that is being made is a set of four, making them end grain doesn’t make much sense. On the other hand, if several matching sets are desired, it’s much easier to accomplish that with the end grain than with the long grain.

It’s impossible to cover all the different design options or techniques for making coasters, but we will look at a few different methods, leaving the ultimate design choices for the woodworker who will make them.

Live Edge Coasters

Live-edge tables and countertops have become very popular in recent years. This has spilled over into creating other applications for live-edge slabs and log slices, with them being used for serving platters and even coasters. Live-edge coasters are easy to make and visually impressive, sure to garner a comment or two from the guests.

While these coasters can be made of any wood, it should be remembered that the wood will be sliced thin across the grain. Some types of wood are not strong enough to survive usage when cut in that manner, so they should not be used. If unsure whether a particular log will work, cut a slice and see how easily it breaks by hand. If considerable force is required, it will work fine for the coasters.

The other issue with live edge coasters is that the bark might come off. Each tree species is different, and the wood reacts differently as it dries. Oak, for example, shrinks considerably as it dries, but the bark does not. This leaves the bark not very well attached to the wood and makes it easy to peel off. That problem can be solved by filling the space between the wood and the bark with epoxy before cutting the log section into coasters.

Some other species of wood, such as cedar, have bark that doesn’t stay intact. When making coasters out of cedar, it is best to remove the bark rather than try to use it as part of the design. That can also be done in the woods where the bark separates from the wood, such as the oak above.

Making the live edge coasters themselves is relatively simple. Start with a log section between three and four inches in diameter. Square up the end, either perpendicular to the axis of the log or at an angle. An angled cut produces an oval coaster, which can be attractive. Then, using a fence on a band saw, cut as many 3/8” thick slices across the log as needed. It’s always a good idea to cut a few extra in case something goes wrong with one or more of them.

The surface of the coasters will have saw marks, which must be removed. This can either be done with a planer or a sander. I avoid the planer for this, as the force that a planer puts on the wood can quickly chip out the end grain. Instead, I lay the belt sander horizontally and sand the coasters to remove blade marks. Once those have been removed, a palm sander can be used for smooth surface sanding. Placing the coasters on a rubber mat for sanding can keep the coasters from moving while sanding.

Branding & Engraving Coasters

Some people choose to add design work to their live-edge coasters by branding them with personal design. This is commonplace for use in advertising items, but branding the first letter of the family’s name into the coaster or some other symbol that the family identifies with can be attractive.

Rather than branding, laser engraving can burn a wide variety of designs into the surface of the coaster. With laser engraving, each coaster can be given a unique design if that is desired. Sets of coasters can be engraved around a common theme, such as images associated with Christmas.

Live Edge and Resin Coasters

A variation on live edge coasters is using smaller-diameter wood pieces. Small diameter limbs, which we usually throw away, can be cut up on the band saw, making 3/8” thick disks ranging in size from ¼” up to the saw’s capacity. Using various sizes, in the ¼” to 1-1/2” range, to make a mosaic and then filling the space between the slices makes for a beautiful coaster once it is cut and finished.

To do this, select several sticks of varying diameter and cut them into 3/8” to ½” slices on the band saw. Then, set these aside for a month or so to dry. While they can be used with moisture, they will shrink somewhat while drying, so it’s best to ensure they are scorched. I keep a box of these drying on the shelf in my workshop to have them available when I want to use them.

Something will be needed as a mold for potting the wood mosaic. Cheap plastic plates, available at any dollar store, make excellent molds for this. They are often made of polyethylene, which the epoxy will not stick to well, allowing the plate to be removed (but probably not salvaged for reuse) fairly easily.

Make a random mosaic pattern in the plate using randomly sized slices of wood that were previously cut and allowed time to dry. This pattern should be larger than the finished size of the coaster so that the final cut will be through the slices. This will leave some of the coaster edges as a cross-section of the wood slices, with the areas in between showing the epoxy. Spacing between the slices is up to the woodworker’s desire, depending on how much epoxy they want to show.

It is important to glue the slices down to the plate used as a mold, especially the smaller pieces, as they will float in the epoxy. A hot melt glue gun works well for this. Only a tiny dab of glue is required.

With the wood mosaic in place, mix sufficient epoxy to fill the spaces between the slices. To determine the amount of epoxy needed, pour uncooked rice into the plate, filling all the cavities between the wood slices. Level it out just above the level of the slices, and then pour the rice out into a measuring cup. The resulting measurement should equal the amount of epoxy needed for potting the trivet.

Epoxy compounds used for potting wood are different from those used as adhesives. They are thinner in viscosity and have a longer working time and correspondingly longer drying time. They can either be used as they come, which will harden clear, or dyed ground mica can be added to the epoxy while mixing it to tint it a variety of vibrant colors. Allow the potted coaster at least 24 hours to cure completely before working further on it.

At this point, neither the top nor bottom surfaces of the coasters will be smooth and level. It will be necessary to take some material off the surface to level them. However, I’d avoid using a planner for this. When I tried using a power planer, the wood slices couldn’t withstand the force being applied by the tool. It tore the casting apart, splitting the wood slices apart, even though I only took a skinny slice off the surface.

Rather than a planer, I’d recommend using a planing bit in a router or a belt sander. A straight bit can be used as one if a planning bit is unavailable. To use the planning bit in the router, a jig will be needed to bridge across the casting, holding the router at a consistent level above it.

These are commonly used when doing river tabletops and other projects using epoxy casting with wood. The only real difference is that this bridge would need to be much smaller, as the casting is smaller. The diagram below, which is not to scale, shows how such a bridge might be made out of 1”x 2” lumber. Just ensure that all the pieces are dimensioned the same so that the top surface ends up parallel to the bench top.

Once planted, the coasters can be cut to size and shape and sanded. Remember that they will need a couple of coats of finish, as the epoxy will not cover the entire surface.

Butcher Block Coasters

Another popular way of making coasters is to laminate different-sized strips of wood together as if one were making a small butcher block. This works extremely well when various types of contrasting woods are used together, allowing the wood’s colors to create the design. The different colors of wood can be arranged to go from dark to light, arranged randomly, or laid out in a symmetrical or repeating pattern. There are infinite design possibilities.

This is an excellent project for using leftover hardwood pieces, as only small pieces are needed to make a set of coasters. The coasters are made in a strip, as long as the available material is available, and then cut apart. Since coasters are generally no more than four inches square, the maximum length of the glue-up would be 16” plus three saw kerfs. If material that long is not available, then making two glue-ups the same, which are 8” long, will still produce a set of four coasters.

Before gluing anything, the material must be ripped on the table saw, making pieces 3/8” to ½” thick, however wide is desired. Then, glue them together just like any tabletop. Considering the thickness of the wood pieces, it would be a perfect idea to use cauls in the clamp-up to prevent the laminated piece from bowing out from the pressure of the clamps.

Use a waterproof glue, such as epoxy or Loctite 3, rather than a water-resistant glue. Even though the coasters will be finished with varnish, making them waterproof, there’s no sense taking chances.

After allowing the glue-up to dry for 24 hours, remove the clamps and plane or sand the surfaces level and smooth. If planning, be sure to insert the boards into the planer so that the direction of travel is along the grain to help prevent tear out. Cut the laminated boards into squares or circles the size of the finished coasters, then sand the surfaces and edges smoothly. It is expected to round over the edges slightly in the sanding process.

End-Grain Butcher Block Coasters

Cutting boards can be made in an end-grain butcher block style, and coasters can be made. The significant advantage of this is if many coasters will be made. A 16” long glue-up for typical butcher block coasters will only make 4 to 5 coasters, whereas the same glue-up for end-grain butcher block can be turned into 32 coasters. Of course, this requires more material, but it’s all glued together at once, so there isn’t much more time needed to do the glue-up.

The only challenge with this sort of glue-up is ensuring no gaps are left between the various pieces of wood. Pressure needs to be applied to the glue-up from both directions at the same time. Cauls can help with this and spread the force from the clamp so that pressure is more evenly applied across the entire length of the laminate.

The clamp can be removed once the glue has had ample time to dry. The edges will probably need to be planed or sanded before the individual coasters are cut from the laminate. Doing this to the whole laminate is much easier than individually for each coaster.

Cut the laminate into ½” slices on the band saw. Then, sand them to remove the blade marks, just as I discussed when talking about the live-edge coasters. I would not recommend putting these through the planer to smooth the surfaces, as there is an excellent chance of tearing them out.

Turned Wood Coasters

While not as common, turned wood coasters have one distinct advantage over any other type of wood coaster. They can be made with a lip to catch condensation dripping off glasses, preventing them from dripping onto the tabletop.

Turning a coaster differs from turning a small, shallow bowl or plate. The only thing to be concerned about is ensuring enough of a lip to catch the condensation. However, the one big problem is that turning them will waste a lot more material than the other types we’ve discussed, as each one will need to have a dovetail mortise cut into the bottom to interface with the lathe’s chuck.

A bowl router bit can be used fairly to represent a turned coaster. People who don’t have a router generally use these to carve out compartments in serving trays and plates. Properly done, the finished product looks much like it was turned on the lathe. However, these router bits also offer the possibility of cutting a serving tray, or in this case, a coaster, that is an unusual shape rather than just round.

Finish Coasters

Some people leave wood coasters unfinished so that the wood can soak up the condensation dripping off of glasses. This is not a very good idea, as the moist soaking into the coaster will cause the wood to swell. It will later contract again, but the uneven swelling and shrinking of the coasters are likely to cause them to crack.

The best finish for wood coasters is heavy-duty polyurethane varnish. Apply two to three coats, sanding lightly with fantastic sandpaper between coats. If the coaster has end-grain exposed, such as in live-edge coasters, it may be necessary to apply three coats before the wood is sealed correctly. Once properly sealed, a fourth coat should be applied for appearance’s sake.

It may be desirable to use epoxy as the finish rather than varnish for coasters made using epoxy. Varnish tends to yellow slightly, so if the desire is to retain the transparent appearance of epoxy without any colorant added, then it is better to use epoxy for the finish. It can be mixed and then painted on with disposable paint brushes in the same way that varnish is.

Another thing you may want to consider is adding felt to the bottom side of the coasters. Not only does this help prevent the coaster from scratching the table, but it also makes making the coasters easier. If the bottom side is covered with felt, sanding out the blade marks or making it smooth is unnecessary.

I usually use black felt to cover the bottom of the coasters, as it won’t be as visible as any other color. I start by cutting squares of felt that are more considerable than the coasters. Rubber cement is then applied to the bottom of the coaster, and the felt is stuck in the rubber cement while still wet. Put pressure or weight on the coaster to keep the felt in place while the cement dries. When the cement is dry, a small pair of scissors or a sharp craft knife can be used to cut the felt flush with the edge of the coaster.