Schematic representation of swelling measurements:  a) measuring the diameter of the equilibrium swollen gel sample by a digital compass. Note that you can also use the image analyzing system given above for these measurements to get more precise results.  In this case, you don't need to take the gel out of the solvent. b) immersing back  into the solvent; c) measuring again the diameter of the gel sample.  The average of at least 6-7 measurements using different samples should be taken.