Extreme humidity or dryness is harmful for the classical, acoustic or flamenco guitar. Sudden changes of environmental conditions from dryness to humidity or viceversa must be avoided at all times as this can cause cracks in the wood regardless of how well cured the wood is.
Guitars should never be hung from the wall as humidity which gathers on the wall can be transferred to the instrument. Excessive humidity can soften the glue and cause the woods to separate.
Wood is hygroscopic material which easily absorbs or expels moisture according to the climatic conditions. lt is recommended that you keep your instrument between 40-75% relative humidity of the air. When the humidity is less than 40% the wood could crack and the action change. When the humidity isgreater than 75% the glue might soften resulting in loss of sound and buzzing due to lowering of action.
When the guitar is transferred in the luggage compartment of a plane the strings must be loosened completely.
It is recommended that the guitar should be wrapped in silk material inside the case.
Guitars must never be placed in the boot of a car in sunny conditions, as temperatures can reach up to 75°, which would cause the instrument to burst.
The recommended action for the classical guitar is 4mm. for the sixth string and 3mm. for the first string, taking as a reference the top of the12th fret and the lower part of the string whilst the instrument is properly tuned.
In flamenco guitar string action is lower and as a reference we can give the following distances:
Height between the first string and the 12th fret: 2 mm.
Height between the sixth string and the 12th fret: 2.5 mm.
The guitar must always be properly tuned; when changing strings they must always be tuned up to pitch. At no time should all the strings be removed together as this would cause the top to lose tension. Each string should be replaced individually.
Due to hand perspiration wound strings tend to lose sonority. This can be remedied by removing the strings and putting them back inreverse if this is insufficient the strings can be washed in soapy water and replaced when absolutely dry.
lf the strings develop a sudden buzz when played open it is probable that the winding has lost its original tension or the groove of the nut has deepened. This can be corrected by changing thestrings in the firs tinstance or placing a thin piece of cardboard under the nut if the instrument has been exposed to excessive humidity similar faults can develop.
CRACKS AND WEAR
Although it is not of great importance when a small crack appears either on the top or back of the guitar it should be attended to by the manufacturer or an experienced repairer. When the crack is on the top, loosen the strings immediately.
lf, as a result of excessive dryness or age, the frets overlap the edge of the fingerboard it is necessary to file this excess away. Although this is a very simple job it is advisable that it should be done by a fully experienced repairer.
To clean a spot on the varnish rub with a soft soapy cloth.
Due to the fact that some varnishes are incompatible, should deterioration of the varnish occur it is advisable for any remedial work to be carried out by the original maker.