My wife and I have been working with Turquoise a good bit in our wood turned works. The project titled “Blue Starburst Bowl” received some great feedback along with a couple requests for a blog on our process of inlaying with natural stone.
Unfortunately we have never set out to formally document our process so we don’t have any photos of intermediate steps. Therefore, I’ll do my best to describe the steps in detail.
First you need something to inlay. We have inlaid pens, wine stoppers, and now bowls. Our first attempts were done on pens and wine stoppers since they are small and easy to experiment with plus, if you mess up you won’t be out much time or money. Pretty much anything can be inlaid with stone as long as there is enough material to carve about a 3/16 to 1/4 inch depth. Running shallower than this will present a couple risks such as filling it up with glue too fast which will result in more gaps between stones. Another risk is if grinding/sanding takes you deeper than expected you could find yourself removing your inlay altogether. Going deeper is fine but you will need more stone and more glue to fill the voids. Deeper is a safer starting point than attempting to go shallow. Depth and glue provide the stone the support it will need to stand up to the grinding process and reduces the chances for stones to be knocked out.
One key step in this part is to seal your wood to prevent staining by the glue. I use some friction wax like Mylands and just ensure it is not in the void you plan to glue the stone.
Type of voids
The easiest, in our opinion, is a simple ring. We started by cutting a 1/4” wide groove in a pen and began experimenting. Our first attempts allowed us to experience the risks of going too shallow or using too much glue described above. Other types of voids include natural cracks, beetle holes, knot holes, etc. The blue star burst on our bowl was done using a dremel to hand carve the void. Note that it is also fun to experiment with building up a glue/stone structure on a base material and then grinding/polishing this into a gem like finish. I did this on the top of a bottle stopper and it came out nice.
Glue and Stone Selection
The glue we use is a clear thin CA glue. Activator is used very lightly (as it will discolor the glue) in cases where the stone work is on the side and at risk of the stones falling out before the glue sets. Pens for example with rings going around the pen require a small touch/spray of activator to set the first couple pieces and then we try to set the rest of the stones in place and apply the glue only when needed. The trick is finding the point where stones can be set and worked in place with a slight stickiness and trying to stay ahead of the glue setting. This reduces the amount of glue you add which helps make sure you don’t fill the void with more glue than stone.
We have found that stone selection is important as well. This is still a point of experimentation but generally choosing the largest stone that fits will require smaller stones/chips/dust to be worked in to fill the gaps. My wife who does all the stone inlay continues to refine this technique and we are still learning. Using just stone dust seems to yield a duller look whereas using only large sized stones yields large gaps between stones. Best advice is to just start experimenting and share what you learn!
When you are done gluing in stone the work should look like you have rock candy on it and above the grade/level of the base material. The goal is to bring all the portions of the void inlaid with stone above the surface such that you are grinding the stone down to the surface.
Once the glue is dry we can start grinding down the stone. Different stones have different levels of hardness and turquoise, while not the hardest, is also not soft. I use a steel flat file to grind the stone. I start with about 1000 rpm on the lathe and use the tool rest for support. Consider all points of general lathe safety and remember to watch fingers, eyes, ears, and airways. The file will also eat into your tool rest so please keep this in mind. I start with a gentle approach and move the file slowly into the work until it starts making contact with the stones. You don’t want to get too aggressive because you will risk knocking out stones and having to repeat the above section. Remember patience in this part of the process.
As you grind your way down I like to stop about 1/16” above the surface and check for a few things. First, check to see if any stones were knocked out and need filling. If so, use the same process as above and select appropriate sized stones. We generally go to small chips/dust. Second, see if any gaps need filling with glue. I generally just put a healthy coat of CA glue on at this point to make sure all the little cracks and chips are filled solid. If not they tend to be filled with saw dust and or stone dust making the work look a little dirty. Finally check to see if the work is grinding evenly. With the file bouncing on the work you can have “waves” form in the grinding process from the tool chatter. I increase the speed of the lathe to work that out and even it up.
Now back to grinding and take it all the way to the surface. Don’t be shy. Get the wood with the file too!
Sanding and Finishing
At this point you can finish your work like any other. I start with an 80 grit sand paper and then work all the way up to 800 or 1000 grit. If I find that there are still little cracks and chips filling up with dust then I blow it out with compressed air and use a little mineral oil and a cloth to clean it up. Finally I finish it off with a 3 stage buffing system or just continue with Mylands friction wax or mineral oil.
Good luck and enjoy!