All the woodworking is finished on these two cellos. Now comes the ground. People use this term for many things, but in this case it includes everything I do to the wood before I actually brush on the varnish. First, I want the wood to have a beautiful golden color. Second, I want to seal the wood so that when I brush on the varnish it will not soak into the pores of the wood and look uneven. There are also acoustical reasons for wanting the varnish on top of the wood but not in it.
One of the classic ways to color the wood is with sunlight. Violin makers would hang the “white” instruments in the sun for up to six months, or so I’m told. I use a UV cabinet or “light box” to color my instruments. The florescent bulbs produce ultraviolet light which oxidizes the outside of the wood, coloring it. I also use the light box to dry my varnish. The top picture is of two scrolls, one that has been in the light box for a week and the other which is just white wood.
After I have achieved the color I want, I then seal the wood with a mixture of varnish and fine particulate matter, like pumice, to fill the wood pores and sap pockets. I rub it on in small areas, trying to seal the wood with the least penetration into it.
I tried a slightly different technique on my last two instruments and it was such a success I am trying it again. Most makers will attach the neck into the body before they varnish, that is the method I learned in school. But there are some problems that arise with that. To be able to varnish under the fingerboard you have to remove and re-glue the fingerboard to the neck after varnishing, and the neck can move in different ways that can be problematic, even slight variations in the neck angle can present challenges. One possible solution is to varnish with the neck detached from the body, and attach the neck later. That way the fingerboard stays glued to the neck, and the neck stays exactly where you set it. The one drawback to this is that you must touch up the neck heel to match the rest of the instrument. It becomes more like a neck-set repair to an old instrument. I have been very pleased with the results so far. That is why you see the neck and body hanging separately in the light box.