Now make it!
After finalizing the desing as shown here, it is time to build it into an actual rosette.
For each column of the mosaic tile (20 in this case), a stack of veneers of the correct colors has to be glued; for this design it means 20 layers. Totalling 400 veneer strips!
After gluing all those veneer strips into correctly ordered blocks (20 of them) a strip can be cut from each; the tricky part is to make these strips the correct thickness and also the correct taper: since the tiles have to be arranged in a circle, they have to be narrower on the inside (bottom of the tile’s design) and wider on the outside (top of the tile’s design). If the thicness is not correct, the design can come out narrower or wider, but if the taper is not correct then the tiles won’t come out right and will also not produce a smooth and good looking mosaic.
I use a couple of techniques for doing this, both of them safe even if using (like in this case) some side grain veneer mixed into the stacks. Other techniques i’ve seen and tried tend to damage some of these most delicate layers.
The first method is to plane one side of the block or stack, then cut a slightly oversized slice. A fine bandsaw can be ok for this. Then the strips need to be run through a thickness sander with an angled support fixed on the table of the sander. In order for this method to work correctly, a few things must be kept under control, especially to keep the sandpaper reasonably clean through all those pieces in order to avoid heat build up and clogging. Still, no matter how well everything goes, every strip needs to be checked carefully and often retouched with a scraper for best results.
The second method can be cleaner but has it’s own set of difficulties: if a good tablesaw with a precise fence is available, then it can be used to cut the strips ready to glue. First, you need a specific saw blade for this: it has to be thin, to save material but especially to minimize heat buildup, and then it has to be HSS (high speed steel) to hold it’s sharpness for long enough. Also the teeth need not have any set (or very minimal), so the surface produced is as smooth as possible. Once you have all this working, then it’s just a matter of tilting the blade the right amount (about 0,7º in this case), adjusting the fence to the right position, plane each block and then cut a strip. This method, although more involved to get right, it’s the one i use the most since if done right you can get very good results; also once everything is set, you can cut more strips so it is faster for more than one rosette (assuming your blade holds up).
Now the strips can be arranged in the correct order to make up a stick; this will be glued in a fixture with the correct curvature. That’s the last critical step in order to produce nice looking and correclty aligning tiles: if all goes well, then it’s just a matter of slicing this stick evenly and the tiles are ready to be assembled in the final rosette.