long as it is soluble in the solvent an important aspect of the method is the rate at which water moisture is introduced to coagulate the gel the introduction of water to the cast mixture cannot be too slow or too fast if it is too slow no gel will form in a meaningful amount of time if it is too fast the gel formed will not be cohesive and the final film will not be strong the rate of deposition of water affects the pore size and ultimately affects the leach rate of the entrapped solid generally the water is introduced to the solution at a rate from 1 ppm hr cm 2 to 6000 ppm hr cm 2 preferably at a rate from 30 ppm hr cm 2 to 90 ppm hr cm 2 the solution can be slowly gelled by exposure to ambient moist atmosphere the solution can be coagulated with conventional techniques either by exposure to ambient moisture or by direct application of a water stream to the resulting solution it has been observed that a relative humidity range of 35 80 at a temperature range of 15 to 30 degrees celsius yields acceptable gels within a 1 to 3 hour range the coagulated cellulose material in the form of a cohesive gel with entrapped solid is washed to remove the polar solvent and the salt it is possible to employ alcohols mixed with water but it is preferable that they be kept below a 50 volume ratio after thorough washing of the resulting gel the gel may be dried with any conventional technique such as air drying vacuum drying or press drying 100 g.