Prevest Research Institute is having a working time tester Model: OD46 from Odeme dental research. This is used to test the working time of dental elastomeric impression materials or similar products. The machine is designed following ISO recommendations such as ISO 4823 standard. The instrument is having a digital measurement unit with capacity of 25 mm and accuracy of 0.05 mm.
The working time test usually follows ISO standard. The basic of the test is to deposit an amount of material to be tested in the central block and will cover a distance of 0.25mm as reflected by the chart recorder. Remove the force immediately after completing this displacement to observe behavior of the recorder pen. Repeat the displacement procedure at 15s interval until the chart recorder pen tracing or watch first indicates a decrease in displacement/stem return when the watch is released; it is a sign that the material has started its elastic phase. Working time is the time measured before the return perception.