Pyroplasticity is the material tendency to deform under its own weight, due to a low viscosity during firing.
The measurement of pyroplasticity is particularly important for ceramic bodies that have to be completely sintered, because during the final stage of firing they develop an abundant vitreous phase with a sufficiently low viscosity to cause rapid deformation of the material.
The Optical Fleximeter is an unique instrument to study piroplasticity.
It is interesting studying piroplasticity not only in full sintering ceramic bodies, but also on porous materials. In addition, it is really useful tu study these deformation both in the raw ceramic body and then after the application of its engobe and its glaze.
The example below shows thre different situations:
-The ceramic body 1 reaches a deformation of 2,5 mm. -The ceramic body 2 reaches a deformation of 4 mm. -The ceramic body 3 shows a rate of deformation too high so the instrument cannot follow its behaviour.
If these ceramic bodies undergo their best firing cicles:
-The ceramic body A reaches a deformation of 2864 µm (black curve); -The ceramic body B reaches a deformation of 4267 µm (green curve). -The ceramic body 3 shows a rate of deformation too high so the instrument cannot follow its behaviour.