Dammar

A varnish is often appHed on top of the paint layers. A varnish serves two purposes as a protective coating and also for an optical effect that enriches the colors of the painting. A traditional varnish consists of a natural plant resin dissolved or fused in a Hquid for appHcation to the surface (see Resins, natural). There are two types of varnish resins hard ones, the most important of which is copal, and soft ones, notably dammar and mastic. The hard resins are fossil, and to convert these to a fluid state, they are fused in oil at high temperature. The soft resins dissolve in organic solvents, eg, turpentine. The natural resin varnishes discolor over time and also become less soluble, making removal in case of failure more difficult (see Paint and FINNISH removers). Thus the use of more stable synthetic resins, such as certain methacrylates and cycHc ketone resins, has become quite common, especially in conservation practice. 

East India. Resins. The East India resins are related to the dammars, although they are older and harder. They are not obtained by tapping trees, but are collected where they are found, principally in Indonesia. Because they are semifossil resins, their softening points are high, ranging from about 110—130°C. The East India resins [9000-16-2] have low (20—30) acid numbers. They are soluble only in aryl hydrocarbons and hydrogenated aUphatic hydrocarbons, and are used primarily in coatings. 

Natural resins such as dammar and Manila copal have been described in U.S. FDA Regulations (3). The Material Safety Data Sheets for these products issued by the importer describe them as nontoxic and nonaUergenic. 

The compositions of sheet and shape waxes are also trade secrets. However, they are blends of various proportions of paraffin, microcrystalline waxes, camauba wax, ceresin, beeswax, gum dammar, mastic gum, and possibly other resins. Sheet waxes are marketed in square sheets approximately 80 by 90 mm. Various thicknesses are available from 32 gauge (0.5 mm) to 14 gauge (1.63 mm). 

Sticky waxes are generally composed of resins and wax. A high resin content gives viscosity to the melt, a long plastic range, and a brittle fracture when cooled. No modem formulas are available, but the older recipes usually had rosin, beeswax, and gum dammar as the essential constituents. 

Damm, m. dam, dike, bank (Med.) perineum Dammar-finiis, m. dammar varnish, -harz, n dammar resin, dammar, dammen, v.t. dam, dam up, stop up curb. Dammerde, /. mold, humus (Founding) pit sand. 

Natural resins Burgundy pitch Copal Dammar Japanese lacquer Pine rosin Wood rosin... 

Dammar Trees of family Dipterocapacaea Torch fuel varnish... 

Natural resins Pine resins, sandarac, copals, mastic, dammar, amber, frankincense, benzoe, styrax, myrrh, (plant resins) shellac (animal resin) tar and pitch (from thermal treatment of plant resins or wood) Varnishes, coatings, waterproofing materials, paint binders, ingredients of cosmetic and pharmaceutical preparations... 

Guttiferales Dipterocarpaceae Hopea (dammar) Dammaranes (hydroxydammarenone, dammaradienol), ursanes (ursonic acid, ursonaldehyde)... 

Dammar resin was introduced into Europe in the nineteenth century, mainly as a paint varnish It is still used today since it has good optical properties and low acidity. It is derived from various species (the genus Hopea and Shorea of the Dipterocarpaceae family). It is characterised by tetracyclic triterpenoids of the dammarane series and contains minor amounts of pentacyclic triterpenoids of the series of olanane, ursane and hopane. It also contains a polymeric fraction named polycadinene or [S-resene. Dammar resin triterpenoids undergo oxidation with ageing, as described for the components of mastic resin. 

Figure 3.11 DTMS total ion currents of (a) fresh dammar resin and dammar after (b) 1 week or (c) 2 weeks of artificial ageing. Reproduced from J. Photochem. Photobiol., A, 134, 13, Copyright 2000, with permission from Elsevier...

Two slightly different laser desorption/ionisation methods were developed simultaneously by Karas and Hillenkamp [1] and Tanaka et al. [2]. Whereas Karas and Hillenkamp used small organic matrix molecules to assist and facilitate the desorption and ionisation of analytes (MALDI), Tanaka et al. used ultra-fine metal powders and glycerol. Zumbiihl et al. first analysed natural triterpenoid resins, dammar and mastic, both... 

A study of the photoageing of single triterpenes was undertaken to establish the suitability of the GALDI-MS method [39]. The triterpenes served as a simplified reference system for the more complex natural triterpenoid resins, dammar and mastic. Seven triterpenes were... 

Figure 5.6 GALDI mass spectra of dammar, fresh (a) and naturally aged under different conditions in a window after 7 weeks (b), as well as in the dark (c), under museum conditions (d) and in a window after 31 weeks (e) [36]. Strong oxidation and degradation can be seen after a few weeks under all ageing conditions, and the ageing patterns are very similar. Oxidation under museum conditions is not much more pronounced than in darkness...

Figure 5.7 GALDI mass spectra of mastic. Commercially available mastic (a) in an advanced state of oxidation as can be seen by comparison with really fresh mastic a few days after harvesting (b). As with dammar, oxidation and degradation progress quickly in both light and darkness. The same mastic as in (b) is depicted after natural ageing in the dark after 7 weeks (c), and in a window after 7 weeks (d) and 42 weeks (e)...

Table 5.1 Components of fresh dammar resin, as reported in the literature [34] with corresponding m/z values of the sodium adducts (see Figure 5.6a)...

S. Zumbuhl, R. Knochenmuss, S. Wiilfert, F. Dubois, M.J. Dale, and R. Zenobi, A Graphite Assisted Laser Desorption/Ionisation Study of Light induced Aging in Triterpene Dammar and Mastic Varnishes, Anal. Chem., 70, 707 715 (1998). 

G.A. Van der Doelen, K.J. Van den Berg, and JJ. Boon, A Comparison of Weatherometer Aged Dammar Varnishes and Aged Varnishes from Paintings, in Proceedings of the Conference Art et Chimie La couleur, J. Goupy and J.P. Mohen (Eds), Paris, France, 1998, CNRS Editions, Paris, 2000, pp. 146 149. 

B.G.K. Van Aarssen, H.C. Cox, P. Hoogendoorn, and J.W. De Leeuw, A Cadinene Biopolymer Present in Fossil and Extant Dammar Resins as a Source for Cadinanes and Bicadinanes in Crude Oils from South East Asia, Geochim. Cosmochim. Acta, 54, 3021 3031 (1990). 

J. Boon, and G. Van der Doelen, Advances in the Current Understanding of Aged Dammar and Mastic Triterpenoid Varnishes on the Molecular Level, in Postprints of Fimis, Material Aesthetik Geschichte, International Kolloquium, AdR, Braunschweig, 1998, pp. 92 104. 

---