FRENCH POLISH OF SHELLAC FINISH:
Most fine classical guitars are finished with a shellac applied using the traditional French polish method. Though acoustically superior to more durable finishes such as lacquer, a shellac finish is very delicate and can be easily damaged if it comes into contact with moisture (perspiration), alcohol, heat which exceeds comfortable room temperature, fingernails, shirt buttons, belt buckles, or other hard objects.
Note: Never apply any of the so called guitar polishes to a shellac finish. A polish which contains silicone or alcohol can be particularly problematic.
When playing a guitar that has a French polish of shellac finish you should always place a protective, waterproof cloth between a guitar and yourself to screen a guitar's finish from perspiration and excessive body heat.
If a French polish of shellac finish is marred (for example, it takes on a milky white haze due to contact with moisture), a guitar maker or repair person skilled in the French polish technique may be able to restore a finish's luster using a very mild rubbing compound. In any event, it is not unusual for a French polished instrument which is played regularly to need some touch up work every three or four years.
CHANGING CLASSICAL GUITAR STRINGS:
Before changing a guitar's strings always set a String Bib protective shield (available from stringsbymail.com, see "Essential Guitar Care Investments" above) on a guitar's soundboard, both in front of the bridge (under the strings) and directly behind the bridge so as to protect against accidentally marking a guitar's finish and soundboard. To further protect a guitar's soundboard and finish against gouges caused by the treble string ends whipping loose while bring the treble strings up to pitch, melt a small ball at the bridge end of each treble string before placing a string on a guitar. Place the melted treble string end under cool water to harden the nylon ball.
Remove and replace guitar strings in sequence. If you remove all the strings from a guitar before replacing the strings, the natural doming of a guitar's soundboard under string tension will relax. In which case, it can take a number of hours with full string tension reapplied to a guitar's soundboard before a guitar will sound at its best. NOTE: Most classical guitars should NEVER be strung with EXTRA HIGH tension strings. Extra High tension strings can cause loss of sustain and dead notes (especially on a guitar's first string) and in the worst case bend and warp a guitar's neck.
TUNING MACHINE HEAD MAINTENANCE:
Lubricate each gear at least once a year with a heavy lubricant such as Vaseline. The usual exception involves the sixth string gears. Because many classical guitar compositions require that you re-tune the sixth string to a low D, the sixth string gears should be lubricated more often as use requires.
DO NOT FLEX A CLASSICAL GUITAR'S SOUNDBOARD:
Under NO circumstances should you ever apply pressure to a guitar's soundboard or bridge area either by forcing the top of a badly fitting guitar case down on a guitar's soundboard or by asserting pressure on a guitar's soundboard with your hands. Always pick a guitar up by its neck, never by its body. More than one guitar's soundboard has been severely cracked by being flexed.