Risks due to heat generating during the setting of gypsum plaster

Status:

completed 06/2018

Aims:

Gypsum plaster is frequently used in the production of artistic and handicraft body moulds, in education and in medical technology. The objective of this project is to determine the quantity of heat generated during the setting of gypsum plaster, including under unfavourable conditions, and to determine the resulting hazard potentials from the values obtained. The present simulation study was prompted by an accident suffered by a student at an art college who, in order to produce a mould, dipped her left hand into gypsum plaster mixed according to the manufacturer's instructions, and suffered considerable injuries as a result.

Activities/Methods:

Simulation tests were performed with the same gypsum plaster as that used in the accident situation, and with two comparable products. Measurements of the curing temperature were taken over the duration by means of a probe thermometer in a range of vessel sizes, and documented. The curing pattern of the gypsum plasters was also determined qualitatively and their pH values measured.

Results:

Curing temperatures with maximum values of between 46.9 °C and 50.8 °C were measured for the three gypsum plaster products studied in a 5-litre vessel. Only slightly lower curing temperatures were measured in a 1-litre vessel. The pH values of the mixtures lay in the weakly basic range with only minor variation. With relatively steep rises and shallow decay curves, the temperature characteristic lies within the anticipated range.

The rapid curing of the mixtures in a low temperature range of under 30 °C was notable. With regard to assessment of the likelihood and severity of accidents, a relevant observation is that gypsum plaster becomes very hard whilst still in a temperature range that is not perceived as unpleasant (<30 °C), and that a hand can no longer be withdrawn from the solidifying gypsum plaster mass whilst the temperature is still within a range perceived subjectively as comfortable. The extent to which the heat then acting upon the skin over a longer period at a temperature of approximately 47 °C can lead to tissue damage is the subject of possible further medical analyses.

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