SDS-polyacrylamide gels supplemented with Rhinohide polyacrylamide gel strengthener are strong, and possess no undesirable side effects. Rhinohide is especially suitable for low-percentage gels, large-format gels and gels subject to multiple staining and handling steps. Supplemented gels yield clear, focused bands, high transparency and minimal background staining. It facilitates exceptional imaging of fluorescently stained gels, along with durability, and is compatible with Coomassie and silver staining. Rhinohide polyacrylamide gel strengthener is available as a concentrate for adding to existing acrylamide/bis-acrylamide stock solutions, or as part of a kit that includes a premeasured acrylamide/bis-acrylamide mixture. Each kit is sufficient for preparing one liter of a 30% acrylamide/bis-acrylamide (37.5:1 ratio) stock solution containing the Rhinohide polyacrylamide gel strengthener.