There are a variety of different gel dryer units which are commercially available for different gel drying applications in the laboratory. The exact drying methods used differ depending on the nature and size of the gels involved.
Polyacrylamide gels of standard size can be dried by oven-like air drying systems, while they contain corrosive compounds they must instead be dried by vacuum dryers which feature filter traps. Sequencing gels or multiple standard size products need a large drying surface with drying enhanced by a vacuum.
These are normally dried between two sheets of porous cellophane and come out of the dryer completely flat and clear with a glossy finish. The dried substance can be used for further detection and analysis by photodocumentation, densitometry or autoradiography. This drying process also makes them suitable for long-term storage. There are also heat vacuum method dryers available which can dry gels rapidly and evenly. These types of dryers come with separator traps which capture corrosive liquids and vapors from the gels as they dry.
A manual dryer process is also used in some laboratories. Manual drying uses a solution containing 10% glycerol and 20% ethanol, drying frames and as with other methods, cellophane sheets. In a manual dryer procedure, the gel to be dried must first be equilibrated in a drying solution for a minimum of half an hour to reduce swelling and make it more flexible once dried.
The next step in the gel drying procedure is to place it between two sheets of moistened cellophane after pipetting 1.2 ml of drying solution on top of it. The cellophane sheets containing the gel are then clipped together and left to dry for a minimum of two days. As you can imagine, this is a much lengthier and labor intensive process than that offered by an automated dryer unit. There are also quite a few things which can go wrong along the way in the manual process, which leads to the commercially available units being preferred in most laboratories where resources and bench space permit.
Yet another alternative to manual drying as well as the more expensive vacuum-based drying units is also available. This is a lower-tech but simple and cost effective method of drying gels; both agarose and polyacrylamide gels can be dried using gel drying film; essentially pre-treated film which is used along the same lines as the manual method but resulting in much more rapid drying. This allows the gels to be viewed even as they are drying and provides a virtually gas-impermeable barrier.
The exact type of gel dryer which is preferable for a given application depends on the requirements of the gel and the other parameters of the application in question. Other factors such as available space in the laboratory, resources available and the throughput of gel drying required all come into play in the question as well. For those facilities which have a large volume of gels, however, the commercially available automated dryer units are a very welcome addition to the laboratory worth every millimeter of bench space that they occupy.
