An improved method of producing acetic acid includes condensing overhead vapor from a light ends column and decanting the condensed vapor to a light phase and a heavy phase. The recording medium is made of a photorefractive crystal having a parallel plate shape. The sheeting agent component may include one or more alcohol ethoxylate compounds that include an alkyl group that includes 12 or fewer carbon atoms. The weight of the water on the bottom portion of the sheet serves to hold the wall in place. The parameter value combinations that cause the combination function to exceed a predetermined probability value are selected for testing. The plain and weighted XOR operations may be performed in a single pass.