I decided to turn an old birch burl that was obtained from a friend in Hovland, my home town. The burl weighed about 90 pounds (diameter of 21 inches) with most of the bark gone and signs of decay. I should have left it in my garage, but I am stubborn when it comes to wasting a burl, and birch burls are usually beautiful. Here are several photos of the burl with the cut line marked in blue and the resulting two halves.
There is a decayed area on both halves and the crack line runs up the entire side of the burl. I filled the decayed areas with a mix of fine ground coffee and thin CA glue. This mix acts like a cement and should help hold the burl together during turning. The plan is to attach a face plate in the approximate center of the flat cut area. The next photos show the burl mounted on my Stubby S1000 lathe. I selected the burl half on the left to turn first.
There were many warning signs in this burl. The decayed area extends throughout the center of the burl. Most of this will be hollowed out so not a problem (except if the bowl flies apart) as long as the area near the bottom of the bowl is stable enough for a tenon. As I started to carve the bottom and turn the tenon, I had to add more of the coffee/CA glue mix. I took the burl off the lathe several times to do this and finally turned what appeared to be a stable 5.3" tenon. The next photos show this. The burl held together well and I managed to turn the profile of the bowl. I was feeling optimistic at this point.
The tenon is secured in a chuck and the piece is reverse mounted on the lathe. I also attached the live center tail stock to add more stability as the bowl is hollowed. I hollowed as far as possible with the tail stock rotating center firmly in place. The next photos the hollowing process. There was decay along the crack and in the bottom, but the tenon held just fine.
It took an entire day to turn this bowl. Was it worth it? Time will tell. The bowl has to dry for several months, be sanded and oiled, and then its beauty will shine. I will be applying thin CA glue to the separating grain lines as it dries to prevent new cracks from starting. The final image shows the turned bowl sitting next to its mate, the un-turned other half. I have not decided if it is worth turning the second half.
This bowl was sanded and finished on May 26, 2020, during the stay at home isolation of the Covid-19 pandemic. I never turned the second half since it was way too time consuming. Sanding the one shown above was also very tedious since there was a lot of grain separation and actual voids around the filled decayed areas. I almost gave up but decided to take the extra time to fill the decayed holes and the gaps along grain lines. This took an enormous amount of detailed work. The finished bowl actually looks very nice with amazing spalting and interesting dark patterns. The colors include black and many shades of brown with golden overtones. The following photos show the after sanding to 400 grit, sealing with tung oil, and finishing with a thin coat of beeswax in walnut oil (dried and buffed). The size of the bowl is 20" x 14" x 5.5" height with a wall thickness of 7/16".