be part of a regular maintenance program. It is important to note that none of these treatments can withstand the extreme moisture and environmental conditions of wood that is below ground level or in constant contact with a source of moisture.5 While some of these treatments may temporarily protect an artifact from UV degradation, moisture intrusion, insects, and/or wood decay fungi, they will only be effective in extending the service life of aboveground portions of wooden artifacts with regular maintenance. However, all of the treatments described above will change the appearance of the artifacts, a potentially undesirable side-effect: visitors may protest the â€œnewnessâ€? of the finishes, and alterations in the appearance of artifacts change the historic visual relationship between the artifacts and the surrounding cultural landscape, negatively impacting the historical significance of the cemetery. Varnishes, Polyurethanes, Lacquer, and Shellac Transparent film-forming finishes such as varnishes, polyurethanes, lacquer and shellac and are generally not recommended for exterior wood because ultraviolet light readily penetrates the finish and degrades the wood underneath.6 Varnishes and polyurethane finishes will eventually become brittle, crack, and peel as a result of UV exposure (Fig. 14). Lacquer and shellac have very little to no moisture resistance and are extremely brittle, making them unsuitable for long-term protection of wood in exterior conditions.7
Fig. 14. Failure of a transparent, film-forming finish, likely varnish or polyurethane.
Annual Journal of the Association for Gravestone Studies