Now that the purfling is installed, we proceed to finish the outside arching of the back. The arching shape has a profound impact on the final tone of the instrument. Over the years I have settled on a particular arching shape for the Strad model that I find reliably produces an instrument with exceptional tone.
The first step is to rough-in the arching using the chisel.
![david-arching-rough Roughed-in Arching](http://www.gbhembree.com/wp-content/uploads/2010/02/david-arching-rough.jpg)
We now move to finger planes and scrapers to refine the arching.
![david-arching-refined refined arching](http://www.gbhembree.com/wp-content/uploads/2010/02/david-arching-refined.jpg)
Finally, we use contour lines and scrapers to clean up irregularities in the arching shape.
![david-arching-clean-up arching clean-up](http://www.gbhembree.com/wp-content/uploads/2010/02/david-arching-clean-up.jpg)
There is a .75mm channel cut all around the instrument at the purfling. The Italians call this the “sgusciatura”.
![david-sgusciatura sgusciatura](http://www.gbhembree.com/wp-content/uploads/2010/02/david-sgusciatura.jpg)
Finally, the arching needs to be brought down a bit and blended into the sgusciatura. Again, contour lines are used to identify irregularities.
![david-arching-scraped arching blended into sgusciatura](http://www.gbhembree.com/wp-content/uploads/2010/02/david-arching-scraped.jpg)
Using a low raking light, all irregularities are found and removed resulting in a perfect arching shape.
![david-arching-finished outside arching finished](http://www.gbhembree.com/wp-content/uploads/2010/02/david-arching-finished.jpg)
Next, we flip it over and hollow out the inside.