Ageing mastic

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 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)...

The resin composition was indeed found to influence the ageing processes in mastic, the polymer fraction was shown to reduce the oxidation of triterpenoids (Figure 5.8). This was found for both natural ageing [33, 36] and artificial ageing. Because the polymer, a polymyrcene, contains many double bonds that can easily be oxidised [42], it might act as a radical stabiliser. The mastic samples shown in Figure 5.8 were obtained from three aliquots of the same mastic solution, the polymer part of the first aliquot was removed and added to the third. 

Figure 5.8 GALDI mass spectra of mastic with variable amounts of polymer, artificially aged for 880 h (36] (a) without polymer (b) normal mastic and (c) with added polymer. Oxidation and decomposition is enhanced with lower amounts of polymer, thus the mastic polymer retards oxidation of the triterpenoids...

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). 

P. Dietemann, M. Kalin, R. White, C. Sudano, R. Knochenmuss, and R. Zenobi, Chios Gum Mastic Freshly Harvested vs. Commercial Resin and its Implications to Aging of Varnishes, Z. Kunsttechnol. Konserv., 19, 119 130 (2005). 

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. 

In addition to GC/MS, high performance liquid chromatography (HPLC/MS) has been used to analyse natural resins in ancient samples, particularly for paint varnishes containing mastic and dammar resins [34]. A partial limitation of chromatographic techniques is that they do not permit the analysis of the polymeric fraction or insoluble fraction that may be present in the native resins or formed in the course of ageing. Techniques based on the direct introduction of the sample in the mass spectrometer such as direct temperature resolved mass spectrometry (DTMS), direct exposure mass spectrometry (DE-MS) and direct inlet mass spectrometry (DI-MS), and on analytical pyrolysis (Py-GC/MS), have been employed as complementary techniques to obtain preliminary information on the... 

Numerous laboratory studies in mammals have demonstrated that ricin and abrin are highly toxic and potentially fatal to animals and humans. Major symptoms of both ricin and abrin poisoning are dependent on the route of exposure, the dose (or number of beans) received, or the content of toxin in the seed (or age of seed). Upon ingestion, toxicity is dependent on the degree of mastication if the bean was... 

Comparison of the results of analysis of fresh and aged materials can lead to very different conclusions. For example, in the case of dammar and mastic, it is very easy to distinguish between the fresh samples of these resins, but after extensive artificial aging, dammar will retain its characteristic profile while mastic can give a completely unrecognizable one. °... 

Shediinsky, A.M. and N.S. Baer, Py-GC Analysis of Aged Damar and Mastic, unpublished results. 

Rosin family s most common form of adhesive is colophony, a hard amorphous substance derived from the oleoresin of the pine tree. This material is applied in solvent solution form as a hot-melt mastic. It has poor resistance to water, is subject to oxidation, and has poor aging properties. Plasticizers are usually added to reduce its brittleness. Bond strengths are moderate and develop rapidly. These materials are used as temporary adhesives in bonding paper and as label varnishes. They are also used as components of PSAs based on styrene-butadiene copolymers and in hot-melt adhesives and tackifiers. These materials have been largely replaced by synthetic-resin adhesives. One specialized form of rosin adhesive is Canada Balsam, covered by the obsolete Military Specification MIL-C-3469C, titled Canada Balsam. This material was intended for cementing optical elements. 

Mioche, L., Bourdiol, P. and Peyron, M. A. (2004). Influence of age on mastication effects on eating behaviour. Nutrition Research Reviews, 17,43-54. 

Compounding was performed in an open two-roll mixing mill (laboratory size). NR was first masticated on the two-roll mill for about 2 3 min followed by addition of the ingredients. Cure characteristics were analysed using an oscillating disk rheometer (Monsanto R-lOO) at a temperature of 150 °C. The composites were cured at their respective cure times in a hydraulic press under a pressure of about 120 bar at 150 °C. Aged samples were prepared by keeping the samples in a hot air oven at 70 °C for 7 days. ... 

Resins largely amorphous, solid or half-solid, transparent, odorless and tasteless organic substances, usuaUy of vegetable origin. Tree R. are clashed according to age into fossil R., such as amber, recent fossil R. (several years to centuries old), e.g. copal R and recent R., which occur mostly as balsams fresh from injured trees. Caoutchouc (see) is included with the R. Herbaceous plants produce R., e.g. mastic, but not in any considerable quantity. Mixtures of R. with mucin are called gum R. Solutions of R. are referred to as balsams. The most important animal R. is shellac, produced by the female East Asian scale insect (Tachardia lacca). 

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