Post By Doug
This is a technique shown in one of my books. I had to try it to see if it was as easy as it seemed. It was.
Use about any kind of blunt tool to indent the wood fibers, don't tear the fibers. Remove all the surface wood down to the depth of the indentation. Pour on boiling water and like magic the compressed wood swells back up to leave a raised figure.
For the test I drew a lame looking leaf in CAD with a few arcs, overall length 4", hard maple. My tool is a 3/16" diameter ball end jeweler's dapping punch. I programmed the machine to follow the lines at a depth of .045". Then face milled to depth to remove the surrounding. It appears to have raised back about .035"
My intention is to use the technique to apply designs, like a pattern of raised dots or similar to turned bowls. Maybe next test I'll try to vary line width for a more pleasing look.
Google on "Ukibori" for a better description of the process.
Cool technique Doug! If you hand plane or finish sand the surface first, does it end up smooth enuf for final finishing? Are the fibers sufficiently bruised to affect the way they take finish or stain?
I'm thinking one could make some decorative punches and end up with a neat textured surface. Maybe try it with some letter/number punches. If I have some spare time (unlikely) I'l give it a go.
Which book Doug?
Originally Posted by richard newman
The book is "Decorating Turned Wood", Liz O'Donnell. Large format paperback, I got a used copy off Amazon. The description of the technique in the book is not as good as Google results showed.
Finishing, I don't know, I'm a total novice in that area. Think of pouring boiling water on a piece of wood. It does seem smoother after drying than I expected, but a fine Scotch Bright might be needed.
Yeah, the idea of decorative punches was in the book. They had a spring loaded automatic center punch with a shaped head to make the indentations.
There's something I noticed in the process that may also have promise. Again, my process was to face mill the wood to get a flat surface, indent, then face mill off to the depth of the indentations. At the point after the last face milling, looking at the surface there was a noticeable ghostlike image of the indentation due the denser, compressed wood. You couldn't feel it. Skip the boiling water, by using a non grain raising dye I wonder if you couldn't get a very subtle pattern effect on the wood where the dye penetrated differently between the dense and not so dense wood.
Doug, interesting idea with the dye, you should try it and let us know. Probably tricky to get it even, but your method with the cnc is as controlled as can be.
The same technique can be used to make a trough that will hold water without leaking. Take a good sized piece of bare wire and knock it all around the joints in the tub before assembly. Plane the wood down flush with the wire trail. When the tub is filled,the wire dents will raise and seal the seams in the tub. I had to make some long slack tubs for the museum black smith shop and used this old trick.