	Soda–lime glass undergoes a steady increase in viscosity with decreasing temperature, permitting operations of steadily increasing precision. The glass is readily formable into objects when it has a viscosity of 10 poises, typically reached at a temperature around 900 °C. The glass is softened and undergoes steady deformation when viscosity is less than 10 poises, near 700 °C. Though apparently hardened, soda–lime glass can nonetheless be annealed to remove internal stresses with about 15 minutes at 10 poises, near 500 °C. The relationship between viscosity and temperature is largely logarithmic, with an Arrhenius equation strongly dependent on the composition of the glass, but the activation energy increases at higher temperatures.