Thermal behaviour of clays and clay-water mixtures for pelotherapy

Variations in the Texture Profile Analysis (TPA) Properties of Clay/Mineral-Medicinal Water Mixtures for Pelotherapy: Effect of Anion Type

“…The thermal behaviour of clay/water mixtures is defined by parameters such as specific heat capacity and cooling kinetics. To calculate the specific heat capacities of the clays, we used the equation proposed by Armijo et al [19]. The velocity of heat loss is important, and this can be determined using curves of temperature decrease over time (cooling curves) and its derived variable: relaxation time (t r ) [19].…”

“…The flask was filled with the sample eliminating the air bubbles. The temperature probe was introduced through the hole in the cap, and the vessel was placed in a hot water bath at 45 • C. When the probe reached this temperature, the flask was kept for 30 min in the bath to evenly distribute the heat and was then introduced into another bath at 36 • C. Using a thermometer with a Pt 100 probe, the temperature of the sample was measured at 15 s intervals until a temperature of 36 • C. The software package Origin 8 (Origin Lab Corporation, Northampton, MA, USA) was used to obtain temperature vs. time graphs and to describe the equations for the curves that best fitted the experimental data [19].…”

“…Considering the percentages of the different waters used to prepare the clay/water mixtures with the same hardness of 300 g, it is possible to calculate the heat capacities and, therefore, assess their potential thermotherapeutic effects [31]. To calculate the specific heat capacities of the clays, the equation proposed by Armijo et al [19] was used.…”

“…This measure is defined as the time needed for a variable in exponential decrease to fall from its initial value by 63.2% of its amplitude. In this case, for a starting temperature of 45 • C and a final temperature of 36 • C, the amplitude is 9 • C and the first relaxation time t r will be the time taken for the temperature to drop to (36 + 9/e), that is, 39.3 • C [19].…”

Healing and edible clays: a review of basic concepts, benefits and risks

“…Local vasodilatation and hyperaemia improve blood irrigation and circulation in the skin and underlying tissues; liberation of histamine and acetilcoline; and modification of serum levels of amino acids (Pastor 1998;Fernán-dez-Lao et al 2012;Sarsan et al 2012;Maraver 2013;Tricás et al 2014). The thermotherapeutic action of both therapeutic mud and peloid provided by the heat very much depends upon the thermal properties of these materials, such as specific heat (the highest possible), heat capacity (the highest possible) and cooling rate (the lowest possible), which values depend upon the texture, the nature and quantity of the solid phase, as well as the nature and quantity of the liquid phase (Armijo 1991;Armijo et al 2016). These authors found that for clay pastes with 60% water the cooling rate is slower for bentonite-based peloids than for kaolin-based peloids, different behaviour that in our opinion could be justified by particle size and distribution as well as by particle aggregation.…”