Paraffin Wax

Properties keywords:  temperature dependent, Newtonian liquid, low melting temperature, water insoluble

Analogue keywords:  basaltic lava flows, ductile crustal rocks, solidifying lava crust

Common names: CnH2n+2,

General Information:  Paraffin wax is a white or colourless solid wax, derived from petroleum.  It is solid at room temperatures and begins to melt at a low temperature.  It is cheap, easily available, non-toxic and chemically inert.  It will burn readily but not ignite.

It is typically used as a lubricant, for electrical insulation, candle making and in the cosmetic and food industries.

Properties

Paraffin wax has a viscosity that is highly temperature dependent, (Figure 1) varying by 9 orders of magnitude (e.g. from 1010 – 10 Pas, Mancktelow, 1998; Rosetti et al., 1999).  At temperatures below approximately 35°C the wax is in a cold solid phase and behaves in a brittle manner.  Above this temperature it will begin to melt and behave as a plastic and deformable solid.  Once temperatures reach the melting point of paraffin wax, which can vary between 40°C and 80°C with wax type, it becomes a liquid with Newtonian properties (Ragnarsson et al., 1996; Rosetti et al., 1999).  These properties are useful for magma analogue experiments because of the wide temperature range between solid and liquid states and the fact that wax requires little heating before completely molten.

Typical densities range from 600-900 kg m-3 and thermal diffusivity is on the order of 10-6 to 10-8 m2 s-1 (Rosetti et al., 1999; Karlstrom and Manga, 2006; Currier and Marsh, 2015).  The tensile strength of paraffin wax is also dependent on temperature (Figure 1), however this parameter is poorly constrained at temperatures nearing the melting point, where it is thought to drop rapidly (Miyamoto et al., 2001; Miyamoto and Crown, 2006).

Figure 1. Temperature dependence of a) paraffin wax viscosity, from Rosetti et al. (1996) and b) tensile strength, from Miyamoto et al. (2001).

Paraffin wax experiences a volume change with temperature, whereby it shrinks by approximately 10% as it solidifies and a further 4% at the solid-solid transition (Ragnarsson et al., 1996).  It is insoluble in water but soluble in most organic solvents.  It has a boiling point > 370°C.  It is also useful for preserving 3D structures after an experiment.

Applications

The properties of paraffin wax make it an attractive lava analogue because, in both materials, heat transfer and mixed brittle-ductile deformation govern the resulting surface features (e.g. Karlstrom and Manga, 2006).  Furthermore, two dimensionless parameters, Reynolds number and Peclet number, are in the same range as basaltic lava, 101~102 and 103~105, respectively (Miyamoto et al., 2001).

Due to its solidifying nature it has been used to simulate the cooling crust of a flowing lava flow, enabling the similarities in surface morphology between wax and basaltic lava to be fully analysed (Miyamoto et al., 2001).  The importance of a solidifying crust was also noted for the formation of pahoehoe breakout lobes in the experiments of Miyamoto and Crown (2006).

It has also been used to represent liquid magma by injecting it into layers of sand to understand the effect of dyke intrusion on host rock deformation on Mars (Wyrick et al., 2014).  Intrusions were removed whole after cooling and hardening and observed in 3D.  Currier and Marsh (2015) injected paraffin wax into gelatine to simulate shallow intrusions into elastic host rock.  They deduced that wax was an effective analogue material as it reproduced the solidification necessary for laccolith formation.

Other studies have used paraffin wax to simulate the deformation of a solid ice layer overlying a liquid ocean on Europa (Manga and Sinton, 2004), and the production of surface rifting patterns observed on basaltic lava lakes and spreading tectonic plates (Ragnarsson et al., 1996; Karlstrom and Manga, 2006).

Limitations and tips for use

As mentioned previously, paraffin wax comes in a range of types and therefore its physical properties will vary significantly between them.  The fact that the wax properties nearing the solid state are poorly constrained also means that it is difficult to quantitatively relate paraffin wax to lava (e.g. Miyamoto and Crown, 2006). 

The material also cannot replicate the variable cooling of a lava crust nor the development of cooling cracks on its surface.  It is, however, useful for understanding the effects of a solidifying crust on lava flow.  Injections of hot wax have been shown to partially melt the host material, changing its deformation behaviour from elastic to viscous (Currier and Marsh, 2015).

No harmful effects are expected from inhalation or contact with skin and eyes, although care must be taken not to burn the skin when handling hot wax.   The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit for paraffin wax fume exposure of 2 mg/m3 over an 8-hour workday.  Although insoluble in water paraffin wax is easily cleaned with ethanol.

References

Currier RM and Marsh BD (2015) Mapping real time growth of experimental laccoliths: the effect of solidification on the mechanics of magmatic intrusion. Journal of Volcanology and Geothermal Research 302: 211-224

Karlstrom L and M Manga (2006) Origins and implications of zigzag rift patterns on lava lakes. Journal of Volcanology and Geothermal Research, 154: 317 – 324

Manga M and A Sinton (2004) Formation of bands and ridges on Europa by cyclic deformation: Insights from analogue wax experiments. Journal of Geophysical Research: Planets, 109, E09001

Mancktelow NS (1988) The rheology of paraffin wax and its usefulness as an analogue for rocks. Bulletin of the Geological Institute of the University of Uppsala 14: 181 - 193

Miyamoto H, Itoh K, Kogure J, Tosaka H, Tokunaga T, Fukui K, and Mogi K (2001) Experimental studies on non-Newtonian fluid flows as analogues of lava flows: toward a numerical model with a cooling crust. Journal of Theoretical and Applied Mechanics, 50: 351 – 356

Miyamoto H and Crown D (2006) A simplified two-component model for the lateral growth of pahoehoe lobes. Journal of Volcanology and Geothermal Research 157: 331 – 342

Ragnarsson R, Ford JL, Santangelo CD, and Bodenshatz E (1996) Rifts in spreading wax layers.  Physical Review Letters 76: 3456–3459

Rossetti F, Ranalli G, and Faccenna C (1999) Rheological properties of paraffin as an analogue material for viscous crustal deformation. Journal of Structural Geology 21: 413 – 417

Wyrick DY, Morris AP, Todt MK, and Watson-Morris MJ (2014) Physical analogue modeling of Martian dyke-induced deformation. Geological Society, London, Special Publications.