This proposal addresses bilayer swelling experiements on floating supported bilayers (FSBs) in the presence of biological buffers. Previous work on multilamellar vesicles has shown a dependence on buffer concentration on swelling. Comparing this previous work with measurements on floating supported bilayers allows a direct comparison upon the differences in the effect of the confinement regime to be investigated, and will provide information regarding the basic physics of fluctuation induced interbilayer repulsion in these systems. Its is also important for future FSB reflection experiments that the influence of common buffers on the behaviour of these increasingly popular FSB systems is understood. This experiment, then, represents the first in a series of detailed and systematic investigations of the effect of ¿standard¿ biological buffers upon the FSB enviroment.