The following text is excerpted from my book The Papermaker’s Companion, with a few additions.
This restraint drying system is the highest-tech system I’ve seen, and it yields flat and dry papers in about 24 hours. I use it myself. The laminated cardboard is a bit costly, but this system is very efficient. It consists of interwoven layers of blotters, paper, and cardboard. Your paper sits on the blotters, which are absorbent and act as a barrier between the cardboard and the paper. Air from a fan blows through the channels in the cardboard, which dries the blotters and, subsequently, the papers. This system is designed for production papermaking. I wouldn’t bother with it if you are not planning to make paper on a regular basis.
MATERIALS AND EQUIPMENT
Biwall or triwall cardboard: 2 or 3 layers of cardboard that are laminated together): a colleague recently purchased triwall from U-line. You’ll need to call and speak to someone to make sure you are getting triple wall cardboard. Update: Staples now carries 4′ x 8′ sheets of triwall.
(Optional) Aluminum Window Screen: I purchased a roll of this at my local hardware store and cut it to fit my drying box. It adds another layer for air to move around and prevents the channels in the cardboard from collapsing due to moisture.
Cotton printing blotters: available at a good art supply store. You can also use cotton linters. I recommend using smooth blottters, because any texture will transfer to your paper.
➤ Make sure that the channels of the cardboard run perpendicular to the fan, so that the air from the fan blows through the channels in the cardboard. You will need one piece of biwall or triwall and four blotters per layer.
You’ll have to determine the size of your drying system based on the size of paper you typically make and the cardboard size. My drying box is approximately 20″ x 26″. The cardboard cannot be stacked higher than the fan. I have about 22 layers in my drying box.
Pictured above you see my drying box before the paper is loaded. There is a piece of 3/4″ plywood on the bottom (it is just sitting on top of that shelf) and there are two large eye hooks attached on either side for attaching tie down straps.
To load your drying box, set your fan on the edge of a table or flat surface. Set a piece of triwall corrugated cardboard flat in front of the fan and place two blotters on top of it (the blotters should be no larger than the cardboard — two layers protect the cardboard from getting too wet).
Next, place as many damp sheets of pressed paper side by side on top of the blotter as you can fit. Put another two blotters on top and then another cardboard.
Repeat this layering system until you reach the top of the fan. Make sure you stack your system evenly, and do not stack above the top of the fan.
I have a second piece of 3/4″ plywood cut to the size of the triwall that I place on top of the stack. Cover the sides of the system with a piece of plastic sheeting, leaving the front and back ends open. Tape the plastic to the sides of the fan to help direct the flow of air from the fan through the stack and maximize the efficiency of the system. The piece of red paper you see sticking out marks the top layer containing wet paper, so that I don’t have to look through empty layers when I unload the drying system.
Place a sheet of cardboard or a board (I have two metal sheets) against the two sides to keep them flat against the edges of the stack. Stretch the tie down straps from one side of the eyelets to the other and cinch them tight. The (two) two by fours with angled ends you see on top of my drying system reduce the stress on the tie down straps.
Alternately, you can put weights, such as cinder blocks or buckets of paint, on top of the stack to keep the sheets flat as they dry (see the first image above).
Turn the fan on high and check the sheets in 24-48 hours. When the sheets are dry, unload the system.
Do you have other drying tips and tricks? I’d love to hear your comments.