Gum Rosin

Properties keywords:  Newtonian, viscous, liquid, glassy, solid.

Analogue keywords: silicate melt, partial melt, solid.

Common names: rosin, Greek pitch, colophony, E915.

Properties

General information: Gum rosin has an excellent Wikipedia site (http://en.wikipedia.org/wiki/Rosin) that covers much of the background to gum rosin and you are recommended to read this as background to the volcanological application.

Gum rosin is produced by the removal of volatiles from the resin (http://en.wikipedia.org/wiki/Resin) of various pine species; the distillate is turpentine and the residue gum rosin. Gum rosin is a soup of natural plant compounds, the main components being [Gören et al., 2010]: (1) the monoterpenes alpha-pinene, beta-pinene, and delta3-carene, and (2) the diterpenic resin acids palustric, abietic, kaur-9(11)-16-en-18-oic and neoabieti. A major chemical constituent is abietic acid (abieta-7,13-dien-18-oic acid, molecular weight 302g, http://en.wikipedia.org/wiki/Abietic_acid). The presence of an HO-C=O group allows gum rosin to interact (H-bonding) with itself and other oxygenated organic compounds including alcohols (R-OH), keytones (RC(=O)R') and ethers (R–O–R'); a key component of the usefulness of gum rosin to volcanological study.

Health and Safety: Gum rosin is widely used across industry, including as a foodstuff; it has an E-number (http://www.food-info.net/uk/e/e915.htm). There are health issues concerning allergic reaction, especially to dust and the volatile compounds released by heating. If gum rosin is being mixed with a volatile organic solvent then the safety of the solvent must also be considered and is likely to be the main health and hazard concern. A datasheet for gum rosin is available at (http://www.newportglass.com/amsgrosn.htm).

Health and safety must be designed into any analogue experiment.

Gum rosin is a natural material produced using a range of distillation parameters. This means that although all gum rosins should have broadly similar properties and behaviours, different batches of gum rosin will differ in the specifics of their physical, and potentially chemical, properties.

At room temperature gum rosin appears a glassy, brittle, transparent solid with colours ranging through yellows, browns and possibly orange. At elevated temperature gum rosin becomes a liquid at 'human' timescales (seconds to minutes). Gum rosin may be considered similar to aluminosilicate glasses in that it is a visco-elastic material. Even at 20°C gum rosin can deform viscously given sufficient time [Bagdassarov & Pinkerton 2004]. At ~ 40°C gum rosin will respond more like a brittle (frozen) solid to strain rates > 1 s-1, and more like a viscous (melted) liquid when strain rates are < 1 s-1. There is not a sudden change in properties at a strain rate of 1 s-1, but a more gradual change over 2 - 3 orders of magnitude of strain rate. Gum rosin was also inferred to have a yield strength.

This complex rheological behaviour, dependent on temperature and timescale of deformation, has similarities to the behaviour of silicate melts and glasses that comprise the volcanic system [e.g., Webb 1997]. This makes gum rosin a potential analogue material to study the behaviour of hot rocks under a range of deformation conditions [e.g., Cobbold & Jackson 1992]. In the laboratory, experimental temperatures will be < 100°C, considerably easier, cheaper and safer to work with than an alumino-silicate at several-100°C, especially with significant volumes of material.

Applications

Gum rosin potentially forms a useful analogue for lava flows, with hot (80°C +) gum rosin as the analogue magma source. As the gum rosin cools it will increase in viscosity and solidify (strain rate dependent) in similar fashion to liquid rock. However, we are not aware of gum rosin being used in this context (but please let us know if it has!).

Gum rosin has been used in the analogue study of magma flow and degassing in volcanic conduits [e.g., Phillips et al., 1995; Lane et al., 2001; Mourtada-Bonnefoi and Mader, 2001; Ryan, 2002; Bagdassarov and Pinkerton, 2004; Mourtada-Bonnefoi and Mader 2004; Lane et al., 2008; Stix and Phillips, 2012.]. For these studies gum rosin is mixed with a volatile organic solvent; gum rosin is the analogue liquid rock and the organic solvent the analogue volatile (H2O, CO2).

Gum rosin organic solvent solutions used experimentally are liquid at room temperature, compared to 'pure' gum rosin being a solid. When the ambient pressure is reduced below that of the saturated vapour pressure of the volatile organic solvent above the solution, saturation has been exceeded and active degassing occurs. Therefore, gum rosin organic solvent solutions at room temperature (20°C) and low pressure become analogous to a volatile saturated magma at much higher temperature (i.e., 800 - 1300°C) and pressure [Figure 3 of Phillips et al., 1995].

The analogy is maintained because, as both systems degas, liquid viscosity increases. Phillips et al., [1995, Figure 2] and Mourtada-Bonnefoi & Mader [2004, Figure 4] compare the viscosity of both magmatic and gum rosin systems. Comparing hydrated magma with gum rosin organic solvent on the basis of weight percent of the volatile in the melt does not attempt to scale appropriately for the physics of exsolution. When dissolved, the volatile can be considered to have a partial density similar to that of the pure liquid 'volatile', i.e., in the region of a few 100 to 1000 kg/m3. On exsolution into the gas phase density decreases by a factor of 100 to 1000, driving the expansion of the exsolving system. Scaling of this phase transition in terms of the driving force is better achieved by expressing the dissolved volatile concentration in terms of moles per unit volume of liquid, with each mole of volatile exsolved expanding to a similar volume. There are other considerations, but Figures 1 from both Lane et al., [2001] and Stix & Phillips [2012] compare the magmatic and gum rosin systems in this context. Please note that the equations given in Figure 1 of Lane et al., [2001] are incorrect. Alternative formulations are given by Mourtada-Bonnefoi & Mader [2004] and Lane et al. [2008], but you are recommended to make your own independent tests.

Acetone has commonly been used as the organic solvent with gum rosin. Acetone vapour pressure [e.g., Kaye and Laby (http://www.kayelaby.npl.co.uk/chemistry/3_4/3_4_4.html)] indicates the experimental pressures below which exsolution to a gas will occur; at room temperature this is about 20 kPa. Diethyl ether is less commonly used but operates at higher experimental pressures, i.e., 60 kPa at room temperature. Gum rosin - diethyl ether solutions appear to have better long-term (> 24 hr) stability than gum rosin - acetone, where viscosity can change significantly with time [Lane et al., 2008].

Limitations and tips for use

Solution preparation is key to obtaining reliable results and the outline method here should provide a good framework for the development of your own method. Preparation of a stock solution with a high solvent concentration (say 30%) is the starting point. Prepare the gum rosin by baking overnight at 80 to 90°C in an oven to remove volatiles. Put aside a known weight of coarsely ground or crushed (1 mm) gum rosin. Weight a vacuum flask, stopper and seal (plastic film on at least one opening) and a large magnetic stirrer bar. Add an excess of solvent to t vacuum flask then place on a magnetic stirrer/heater. Stir vigorously and warm gently, taking care not to exceed 50 kPa vapour pressure (56°C for acetone and room temperature for diethyl ether). Slowly add the crushed gum rosin. If powdered too finely it will clump and take a long time to dissolve. Add a small amount and let it completely dissolve to give a transparent liquid, then repeat. Take your time with this process and add more solvent if the viscosity becomes too high. Once all the gum rosin has dissolved you should have a clear brown stock solution.

Calculate the mass of solvent you require to make the correct solution concentration. Weigh the stock solution in its vacuum flask with stoppers and stirrer and calculate the mass of solvent in the stock solution. Subtracting the desired amount gives you the mass of solvent to be removed. Stir and warm the stock solution then use a vacuum pump to remove solvent vapour from the solution. Take care not to boil and foam the solution too much and weigh regularly. The evaporation cools the solution so warm as required. Once the correct weight has been reached seal the flask and let it cool to room temperature.

To test your solution, remove a small sample and weight. Degas in an oven at 80 to 90°C, cool and reweigh. Calculate the solvent concentration and check that this is close to the expected value. Use the measured values for volatile calculation.

If you are storing solutions for future use then retest concentration and viscosity before use. Also note that 1 to 2% of the volatile is likely to be strongly bound and inaccessible to vacuum degassing at room temperature [Lane et al. 2008, Figure 2].

The importance of safety is stressed here. Avoid contact with organic solvents and gum rosin whenever possible:

References and Further Information

Bagdassarov, N., Pinkerton, H. (2004) Transient phenomena in vesicular lava flows based on laboratory experiments with analogue materials. Journal of Volcanology and Geothermal Research, 132, 115–136.

 

Cobbold, P. R., Jackson, M. P. A. (1992) Gum rosin (colophony): a suitable material for thermomechanical modeling of the lithosphere. Techonophysics, 210, 255–271.

 

Fuentes-Auden, C, Martinez-Boza, F, Navarro, FJ, Partal, P, Gallegos, C (2005) Viscous flow properties and phase behaviour of oil-resin blends. Fluid Phase Equilibria 237(1-2), 117-122, doi 10.1016/j.fluid.2005.08.017.

 

Gören AC, Bilsel G, Oztürk AH, Topçu G. (2010)Chemical composition of natural colophony from Pinus brutia and comparison with synthetic colophony. Nat Prod Commun. 5(11),1729-32.

 

Hailemariam, H, Mulugeta, G (1998) Temperature-dependent rheology of bouncing putties used as rock analogs. Tectonophysics 294(1-2), 131-141, doi 10.1016/S0040-1951(98)00124-3.

 

Lane, S. J. & M. R. James (2009) Volcanic eruptions, Explosive: Experimental insights. In Meyers, Robert (Ed.) Encyclopedia of Complexity and Systems Science, 2009, Part 22, 9784-9831, DOI: 10.1007/978-0-387-30440-3_579 Springer New York.

 

Lane, S. J., Phillips, J. C., Ryan, G. A. (2008) Dome-building eruptions: insights from analogue experiments. Lane, SJ; Gilbert, JS (eds) Fluid motions in volcanic conduits: a source of seismic and acoustic signals. Geological Society Special Publication 307, 207-237, doi 10.1144/SP307.12.

 

Lane, SJ, Chouet, BA, Phillips, JC, Dawson, P, Ryan, GA, Hurst, E (2001) Experimental observations of pressure oscillations and flow regimes in an analogue volcanic system. Journal of Geophysical Research-Solid Earth 106(B4), 6461-6476, doi 10.1029/2000JB900376.

 

Mourtada-Bonnefoi, C. C., Mader, H. M. (2001) On the development of highly-viscous skins of liquid around bubbles during magmatic degassing. Geophysical Research Letters, 28, 1647–1650.

 

Mourtada-Bonnefoi, CC, Mader, HM (2004) Experimental observations of the effect of crystals and pre-existing bubbles on the dynamics and fragmentation of vesiculating flows. Journal of Volcanology and Geothermal Research 129(1-3), 83-97, doi 10.1016/S0377-0273(03)00233-6.

 

Phillips, JC, Lane, SJ, Lejeune, AM, Hilton, M (1995) Gum rosin-acetone system as an analogue to the degassing behaviour of hydrated magmas. Bulletin of Volcanology 57(4), 263-268, doi 10.1007/BF00265425.

 

Rossetti, F, Ranalli, G, Faccenna, C (1999) Rheological properties of paraffin as an analogue material for viscous crustal deformation. Journal of Structural Geology 21(4), 413-417, doi 10.1016/S0191-8141(99)00040-1.

 

Ryan, G. A. 2002. The flow of rapidly decompressed gum rosin di-ethyl ether and implications for volcanic eruption mechanisms. PhD thesis, University of Lancaster, UK.

 

Smith, JH, Woodhouse, J (2000) The tribology of rosin. Journal of the Mechanics and Physics of Solids 48(8), 1633-1681, doi 10.1016/S0022-5096(99)00067-8.

 

Stix, John, Phillips, Jeremy C. (2012) An analog investigation of magma fragmentation and degassing: Effects of pressure, volatile content, and decompression rate. Journal of Volcanology and Geothermal Research 211, 12-23, doi 10.1016/j.jvolgeores.2011.10.001.