this being controlled by drainage of the non solvent bath sometimes called the developer bath and pure non solvent is added to the developer tank at the other end where coated fabric or membrane is being taken out of the developer tank and going into a drying tunnel the amount of pure non solvent liquid is monitored to keep the tank liquid level constant for example if the non solvent is methanol which has a very low surface tension it enters the developer tank at the fabric exit end and if the solvent is dmac this is mixed into the methanol by diffusion the high concentration of dmac increases the surface tension of the non solvent in situ such that the surface tension is higher than the pure methanol liquid so the resulting porous membrane has less tensile stress and smaller pore size and is softer as another example if the non solvent is pure water then where the coated film enters the developer tank the solvent e g dmac with a relatively high concentration will lower the surface tension of water and also therefore the compressive stress at the membrane surface so it will not form a very tight skin surface with very small pores instead it will have moderate pore diameter with high porosity the membrane still has a degree of softness suitable for clothing purposes in fig1 151 is the roll of fabric 152 is the fabric under tension to be coated 153 is the knife.