Types of Woods
Wood is a polymer of b glucose and lignine conforming microfibers and fibers. It's the hard part of the tree, after being sawn, dried and cut in different ways.
There are different woods with different weights but the "wood" substance has a specific weight of 1.56. relative to water. The specific density of a particular wood depends on its content of free space (the amount of volume filled with air), which is extremely variable between species, between woods of the same species and even between different parts of the tree.
An important property, which determinates many carachteristics and problems of wood is the fact that wood is an anysotropic material, that is, it has not the same values of contractibility in the different spacial directions. Wood contracts and expands much more in the tangential direction (perpendicular to axis) than in the radial (pointing to the center) or axial (along the fiber or grain) direction. This determines the "working" of wood, its tendency to split apart and deform under variations of humidity and temperature. Damp and hot places will expand wood and cold and dry places will contract it.
Wood needs an environment of constant huimidity and temperature, more or less in the order of a 50-65 % of relative humidity and a temperature of 20 degrees Celsius. In other conditions and specially in constant variable conditions and during a long period of time the periodical contractions and expansions of wood will produce cracks of panels, loosening of joints and of adhesion of marquetry and an appropriate climate for the reproduction of woodboring insects and fungi.
The following is a brief list of the most common fine woods used in antique furniture.
Mahogany. Swietenia mahagony. Used in solid and veneer form. Light golden brown to dark, striped and variable reflections of light. Specific Density: 0.70-0.85. Working: excellent. Biological resistance: excellent.
Walnut. Juglans regia. Used in solid and veneer form. Light brown-grey. Figure very variable upon sawing techniques. Specific Density: 0.60-0.80. Working: excellent. Biological resistance: medium or poor.
Oak. Quercus petrea, pedunculata, alba. Mostly used in solid. Light brown-yellow to dark brown. Figure extremely variable upon sawing techniques. Specific Density: 0.60-0.80. Working: good. Biological resistance: good.
Satinwood. Brosimum paraense, Ferolia guianensis, Chloroxylon Swietenia, Zanthoxylum flavum. Used in solid and veneer. Light golden to dark or reddish. Highly figured. Specific Density: 0.70-0.80. Working: good. Biological resistance: good.
Palissander or Rosewood. Dalbergia nigra, latifolia. Used in solid and veneer. Dark red or yellow-orange and black in irregular stripes. Highly figured. Specific Density: 0.80-1.10. Working: good to difficult. Biological resistance: good.
Tulipwood. Dalbergia variabilis, frutescens. Used mostly in veneer. Light pink with irregular stripes of darker pink or red. Highly figured. Specific Density: 0.75. Working: difficult. Biological resistance: good.
Ebony. Diospyros ebenum, melanoxylon, ebenaster. Used mostly in veneer form. Jet black, uniform surface, oily touch. Specific Density: 0.9. Working: good. Biological resistance: good.
Generally speaking wood has been used in the past for both structure and decorative purposes. As wood for structure, in the Western hemisphere, both pines and/or oaks were used. For surface and decorative purposes a wide "palette" of woods has been chosen: ebony, palissander, kingwood, rosewood, calamanderwood, boxwood, tulipwood, sycamore, maple, walnut, mahogany, satinwood, elm, and many more. In restoration one of the following three criterions is and has been applied to the election of woods in the moment of replacing wood or completing a lack of material:
Replacing or completing with the exact species of wood, and retouching it in order to imitate exactly the original material.
Replacing or completing with the exact species of wood, leaving some differences in color and leaving the matching of edges between the new material and the old one visible, making the restoration noticeable at close range.
Replacing or completing with a different kind of wood and matching color, degree of brightness of the finishing, etc., with or without matching edges, with the same intention as above.
I personally prefer the second option and even the third. My general criterion favours the aesthetic integration of the object, while allowing the easy recognition of the restoration process (it is also recorded in my final reports to the client). The result is an object that can be looked at without the eye being catched by the deteriorated or lacking parts, keeping it recognizable in its age and history.