It is most important to set the strings in motion with a right hand nail that is very smooth to produce a clear strong tone. Never use nail clippers or scissors to shape the nail. There are many nail maintenance products available from cosmetic departments that will ensure a glass smooth surface to the nails. A more economical way is to buy a sheet of 600 grade Silicon Carbide paper and keep this in your guitar case. Pay particular attention to the underside of the nail that comes in contact with the string.
The debate over the use of the nails of the right hand has continued over the years starting in the early 19th century with Fernando Sor who found the nails to be unnecessary; whereas his contemporary Dionisio Aguado felt that the nails were necessary to achieve speed and tonal variation. From Andres Segovia onwards the nail in conjunction with the flesh of the right hand fingers has become the accepted practice.
One of the most perplexing questions encountered by the fingerstyle guitarist is the shape, length and care of the right hand fingernails. The following general advice should be helpful to players who may be having problems in this area.
Remember that the shape, thickness and quality of the nails will vary greatly from player to player so be prepared to experiment in your search for solutions in this area. The right hand nails in conjunction with the flesh at the tip of the finger are responsible for setting the string in motion. If the section of nail which strikes the strings is not smooth and well shaped it will be impossible to obtain a full round sound, and the execution of the stroke will not feel secure if any section of the nail catches on the string. Therefore, the nail must be shaped in relation to the angle that the nail strikes the strings.
The steps below set out a method that will ensure that the nail is shaped at the appropriate angle.
Cut a piece of 600 grade Silicon Carbide paper, available at hardware stores, into a 100 by 200 rectangle. Fold this in half and place it over the strings of your guitar around the sound hole area as shown in the picture below.
Pick up your guitar in normal playing position a play a number of rest strokes on the paper starting with your index finger. Approximately 10 strokes should do. Examine the nail of your index finger and you should see a distinct line across the nail at the precise angle that your nail comes in contact with the string.
Proceed to duplicate Step 1 with the second and third fingers of your right hand as well as your right hand thumb.
Take your nail file (needless to say that this should be a high quality product) and with your right palm uppermost proceed to shape the nail from the left edge up to the line marked by Step 2. You may find that the shorter the nail in this area the more stability the nail exhibits when you execute your strokes.
Next round off the nail from the marked line to the right edge of the nail. Smooth off any edges left at the point where your filing meets the marked line but do not change the angle of this line for this is the area which will come in contact with your strings and must present as wide a platform as possible to produce a strong even tone.
Step 5. The final step involves the polishing of the edge and underside of the nails. With a piece of 800 grade Silicon Carbide paper apply a glass like finish to the edge and underside of the nail.