I was introduced to crushed stone inlay in 2011 at Arrowmont School of the Arts, Gatlinburg TN. The instructor was Stephen Hatcher. He is the Master of crushed stone inlay in my opinion. The week I spent in his workshop changed the direction of my professional turning career. Go to his website and download his pdf’s on stone inlay.
http://stephenhatcher.com/index.php?n=10
Warning!
Crushed stone inlay requires the use of large amounts of CA glue. The fumes are very noxious. The process of sanding stone creates dust that is not as easily captured by a dust collector as is wood dust – your shop may get very messy. Wear a well fitting mask or respirator. Superglue fumes are very irritating to your eyes and respiratory system so keep the area very well ventilated. I suggest you follow the link below to read about the hazards of working with CA glue.
I usually make a wide, undercut rim on my bowls that are going to feature a crushed stone inlay. This design feature gives me lots of room to be creative. I’m sure you know how to make an undercut rim on a bowl.
I use Starbond CA glue in large amounts. I buy it in Bulk. Using very thin CA glue will stain the wood if precautions are not taken. You must protect the wood surface from soaking up this thin CA glue. I use a solution of 90% Denatured Alcohol and 10% one pound cut of dewaxed shellac. Mix this and put it in an industrial type spray bottle. Spray a little on your hand. When it drys in a few seconds, your hand should be slightly sticky. Spray or brush this mixture on the surface of the wood. Apply this mixture every time after you sand the inlay and prior to applying more CA glue.
In my video “Add Crushed Stone Inlay into Your Wood Turnings” we learned about the hardness of the best stone to be used. On the mohs scale we know that minerals between 3 and 5 are best to use. Most hardwood I use are the same hardness as the minerals. Aluminum oxide used in sandpaper has a hardness of 9. Match the hardness of your stone to the same hardness as the wood to get a smooth, level Inlay. Your results will always be great as long as the wood is relatively dry, about 12% or less.
When turning a groove for inlay, the groove needs to be very well defined. If the groove has tear-out in it’s sides, the inlay edge will look sloppy. Prior to cutting the groove it is advisable to cover the rim surface with any finishing wax. Then cut the groove leaving this wax barrier on the rim surface on both sides of the groove. This barrier will keep CA glue from staining the wood as you build up the stone in the groove. The groove must be wax free. If any wax gets in there, retrim the groove for a clean surface.
When doing a beaded, rounded over bowl rim I lay in small and medium minerals as a base because the inlay will be seen on two sides. In Stephen Hatcher’s pdf “Basic Stone Inlay” he recommends laying in the largest of your crushed stones first. In either case, make sure to use ones that are big enough to fit side to side and are proud of the rim. Arrange them based on your sense of what looks good to you. Be random. Now lay in the next smaller size. Be generous. Make sure they have no wiggle room. When satisfied, lay in the next crushed stone size down. Sprinkle them all around the larger crystals. They should fall down to the bottom of your groove and fill in around the larger crystals. Help them along gently by tapping or vibrating.
Add Super-Thin CA glue but use very little CA accelerant. Keep repeating until you have filled in around the larger crystals. Now using the sugar sized crushed stone fill in any holes, voids, cracks and spaces. I sprinkle it on very lightly so that it will fall in around the larger crystals. The idea is to get as much of the groove filled with crystal as possible. Gently tap the wood to help the crystal settle into empty pockets. Sometimes I use an inexpensive electric jewelers engraving tool with a rubber tip to gently vibrate the wood. Be careful! You can easily vibrate or tap everything out of the groove and all over your work bench! You should have a mound of crystal piled up “Proud” of the wood surface but not too proud. Remember! Everything proud of the rim has to be sanded flush.
Use the CA glue liberally. I mean fill that groove so that the glue is almost running out and over the sides. Drip it in and let it soak in. Continue until the crystal is drenched. Let the CA glue dry for at least 24 hours. The super glue will cure to a clear polymer. If done correctly The inlay should look like one piece of molten glass and be very hard and dry.
When you are satisfied it is good and dry the next step is power sanding. If your inlay is overly proud and heavy use silicon carbide [SiC] sandpaper for the initial sanding then switch to Klingspor Stearate A/O 80 grit PSA sandpaper discs on a variable speed drill. You can get them from Klingspor’s Woodworking Shop. The Calcite must be sanded down flush with the wood. Be careful not to build up too much heat on your sandpaper or the inlay.
After you have power sanded the Calcite down to the wood, inspect the surface of the inlay using a magnifying glass. You will notice that there are a few tiny holes and crevices. You must fill those in with the tiny powder size crushed stone and add more CA glue. But not before you spray the wood surface with the Shellac solution again.
Power sand this time using 100 grit paper. Inspect the surface again and repeat the process until the inlay surface is smooth. If the surface is solid, from this point on you will not be using CA glue, so you do not have to spray shellac after sanding. I Power sand the inlay starting with 120 grit and go all the way through 4000 grit. At that point I switch to 2“ Micro-Mesh pads and go to 12000 grit. I then polish with tripoly and white diamond polishing compound. Your Calcite will be polished and gleaming like rubies, emeralds and sapphires!
