The effect of freezing and thawing on the rheological behavior of illite su
spensions was studied by examining viscosity and plasticity. Stability of s
uspensions was characterized by a hysteresis loop of thixotropy. Thermal gr
avimetric and differential scanning calorimetry analysis were also used. Af
ter initial freezing and thawing, the flow curves of the suspensions show a
n increased viscosity, an "irregular up line", and a greater hysteresis loo
p of thixotropy. The ratios of mean viscosity of previously frozen (F) and
control (O) samples (eta(F)/eta(O)) for non-expandable 2:1 phyllosilicates
ranges from 1.3 to 2.1. Addition of monovalent (0.1% Na2SiO3) and divalent
cations (0.3% CaCl2 or BaCl2) increase and decrease the shear-stress differ
ence between F and O samples, respectively. Prior freezing of clay samples
results in an increase of plasticity by similar to 20-30%. The thermal anal
ysis data of F samples show an increase in weight loss, and a decrease in e
nthalpy of dehydration. The changes of physico-chemical properties from cyc
les of freezing and thawing are long lasting. The freezing memory effect of
illite-type clays is expected to play an important role in ceramic process
ing, i.e., casting processes, plastic formation, and sintering.