An ambient pressure gravimetric sorption apparatus is being developed as an alternative technique for studying solubility and diffusivity of solvents in polymers. This apparatus has many potential advantages over more conventional sorption techniques which involve either an electro balance such as the Cahn balance or a quartz spring for determining the mess of a polymer in contact with a solvent. This new apparatus will have the capability of high temperature experiments up to over 200°C and improved flexibility in terms of the size and configuration of the polymer sample employed.