How to Inlay Stone Into Wood
by Tim Carter
Delray Beach, FL
Note: click on any picture to see a larger version.
Want to take a plain project and make it really spectacular? One way to do it is to inlay semi-precious stone into the wood! The inlay can create an amazing contrast of colors and shapes that will draw people to it!
I’m a woodturner and use this process a lot on bowls, platters, hollow forms and Lazy Susans that I turn. However, the process can be used on any type of wood working project.
The process is not difficult and it doesn’t require much of an investment in either tools or materials. The tools you need are a rock crusher, a sorting bowl, a pair of tweezers and occasionally a wire brush. The materials you need are the semi-precious stone and cyanoacrylate (CA) glue, usually the thin type but some situations require the medium or thick varieties.
A rock crusher is easy to make and you really want to use one to keep the stone from flying all over your shop. I used a 6” length of 1” galvanized pipe with a cap screwed on one end to hold the stone. The crusher is a 12” length of 7/8” steel bar that fits into the pipe. I took a piece of scrap wood and turned a handle on my lathe for the steel bar and epoxied it in place.
The sorting bowl can be any bowl you have lying around. I used an ugly bowl I turned on the lathe some time ago that I had good intentions or finishing but never did so. This bowl is used to sort the crushed stone into different sizes to fit the particular inlay you’re working on. Some inlays will be large and require small chunks of stone where others will be cracks that require stone dust to fill. There are other inlays where you’ll want to use a mixture of dust and chunks to create a more interesting look.
The semi-precious stones I use most often are: Turquoise, Malachite, Lapis Lazuli, Azurite, Onyx(black) and Red Coral. They are readily available through a number of suppliers at a reasonable cost. I chose these stones because they provide a great contrast to the woods I use. The woods I use include: Maple, Red Oak, Walnut, Cherry, Norfolk Island Pine, Manzanita burl, Wenge, Bubinga, Canarywood, Padauk and Zebrawood. I’m looking to make a dramatic statement with the inlay and the greater the contrast between the color of the wood and the color of the stone, the greater the impact on the viewer.
If you are going to inlay a turned piece, make sure you’re finished turning the piece before you inlay the stone. Stone dulls turning tools VERY QUICKLY and you’ll end up spending a lot of time at the grinder resharpening your tools.
There are a lot of natural defects in wood that can be inlaid very effectively. They include: cracks from the drying process, termite or worm holes, loose knots and bark inclusions. You also can create your own area to inlay using a Dremel tool with an engraving bit or a marking knife. Using the lathe, you can create grooves of various sizes or round areas that can be inlaid with a combination of wood and stone. Slices of burl in a contrasting color that are either round or oddly sized can create a very exciting visual pattern for the viewer when combined with the stone.
When you’ve determined what area you’re going to inlay and what stone you’re going to use, the area needs to be cleaned out to ensure that the CA glue will establish a tight bond. Use a wire brush to clean it out and then blow the dust and/or particles out.
Put a small amount of stone in the rock crusher and pound the stone with the steel rod 8-10 times. Empty the crushed stone into the sorting bowl and grade it by rapidly tapping the bottom of the bowl against the work bench. Keep the sorting bowl tilted at an angle while you’re tapping it against the bench to allow the stone to separate by size. The larger pieces of stone will move to the lowest point and the stone dust will be at the highest point in the bowl.
Take some of the crushed stone in your fingers and put it into the area to be inlaid. Use as much as necessary to fill the area. Tweezers can be used to set pieces of stone in place to achieve a particular arrangement or look. In order to reduce the amount of sanding that has to be done later, I try to keep the stone below the edge of the wood. When the inlay area is filled and smoothed to your liking, use thin CA glue to set the stone in place. If possible, use a small extension tip on the CA glue bottle to reduce the flow of CA and to give you better directional control of the glue. The thin CA glue will wick through the stone into the wood creating a very strong bond. It usually takes several applications of thin CA to fill the inlay up to the edge of the wood or slightly above. If you are filling a deep inlay, it may work better to use the thin CA initially to set the stone in place and then to switch to a medium or thick CA glue to fill the rest of the inlay. Use CA glue accelerator sparingly to avoid getting those annoying bubbles in the cured CA glue. However, if you do get a bubble in the cured CA glue, use a sharp awl to poke and scrape the bubble to open it up and then apply more thin CA glue. It will usually fill the bubble and cure without any trace of the bubble remaining.
If the hole to be inlaid goes all the way through the wood, use a piece of clear packaging tape on one side of the wood to seal the hole and then add the stone and create the inlay as outlined above. Take the packaging tape off as soon as the CA glue dries. You will probably have to add more stone to replace some that stuck to the tape, using thin CA to set it in place.
At this point you’re ready to sand and finish the piece. In order to speed up the sanding process, I use Power Lock discs in a variable speed drill to sand the inlaid areas smooth before I finish sand the remainder of the piece. I start with an 80 grit disc and work up to 220 grit. Make sure to wear a good dust mask or respirator when you’re sanding the piece! Stone dust is not something you want in your lungs! I finish sand my pieces to 400 grit and then finish with wipe-on poly. The finished piece-a manzanita burl bowl inlaid with malachite is shown below.
You can email Tim at firstname.lastname@example.org.