Proteins are most commonly transferred from the polyacrylamide gel to a blotting membrane through electroblotting. In a tank blot (wet transfer), the gel is sandwiched between two pads or sponges soaked in transfer buffer, and a membrane such as nitrocellulose or PVDF is placed on top of the gel. The stack is then placed into an electrophoresis chamber, and a current is applied to transfer the proteins from the gel onto the membrane. The transfer buffer typically contains a buffer system that maintains a pH and ionic strength that supports protein transfer, along with methanol or ethanol to enhance transfer efficiency. In a "semi-dry transfer" filter paper pads soaked in transfer buffer surround the gel and membrane. The sandwich is placed in direct contact with two electrodes through which an electric field is applied. Subsequently to the transfer, the membrane is blocked to prevent non-specific binding of detection antibodies and then incubated with primary and secondary antibodies specific to the protein of interest. The bound antibodies are then detected by chemiluminescence or other detection methods, and the signal is captured using X-ray film or a digital imaging system.