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Home made coated paper drying box

Here's the problem: OK, you've read about paper coating using (commercial) liquid emulsions or are interested to give alternative techniques a try. Buying emulsion is easy, and coating a piece of paper in darkroom isn't that difficult either. In your enthusiasm, you've coated a whole stack and now intend to let them dry... Darned!!!, I can't leave my darkroom, as opening the door will expose my coated sheets of paper!!!...

or: you've read left over paper boxes are good for drying. Your second try on coating seems to go well, and you leave the papers in the boxes to set and dry. A few hours later you go back in to check them... D#!X!!m, the paper is stuck to the bottom of the boxes lid!! Paper boxes just can't cope with the amount of water released from the coating, and will buckle, causing the paper to get stuck to the lid... This is especially a problem if you are (over-)ambitious (like I was!) and want to coat larger paper sizes (e.g. 40x50cm).

or: you've read a hairdryer might do the job, only to discover that the red-hot heating spirals have fogged your paper...

Been there...

So what to do???

Now there are probably (expensive) commercial drying cabinets available for this problem, but I thought I would give it a try with a home-grown solution. What I have created is a light tight drying box with active ventilation that can hold up to six 40x50cm sheets and dry them safely. So here it is:

What you will need:

- Black 50x65cm developer tray

- Black 5mm foam board, this is a kind of ultralight foam board reinforced with black carton on both sides. Please note that this stuff, although being stiff, is pretty vulnerable and can be damaged easily. You can get this stuff in most office and artist supply shops.

- Black matting carton

- 2mm glass plates for holding your paper, about 40x50cm or slightly bigger if you want to be able to coat 40x50cm sheets. This is just standard glazing glass, 6 plates maximum can be held in a standard 50x65cm tray.

- 10mm aluminium U-beams to stack the glass plates. Can be had at do-it-your-self shops in varying lengths.

- Three 12V computer ventilators from electronics shop or left over retired computers.

- 12V adaptor or left over computer power supply

- Gaffer tape

- Pair of scissors to cut the tape

- Glue

- Vacuum cleaner filters

So how do you do use this stuff?:

- Drill holes at the positions where you want to install the computer ventilators. Glue the ventilators to the box. I have positioned them on the short (right in picture) side of the tray. Glue the computer ventilators to the box, taking care to position them correctly respective to the required air flow. Connect them up electrically and check if they work. In my case, the ventilators suck out the air and are therefore located at the air outlet position. I recommend you to do this as well, as it will create underpressure and keep the lid on top of the box, instead of maybe almost blowing it of... Of course, this construction is far from light safe, so use black matting carton, glue and gaffer tape to create a light-tight air outlet. The light block is constructed to require air (and light) to travel through two full U-turns, effectively cutting out all light. Make sure you've checked electric connections for safety and function before you start constructing the outlet!

Drying box with lid removed

The drying box with the lid removed, air flow is left to right in this image, with the computer ventilators hidden in the right outlet protrusion. Notice the vacuum cleaner filter covering up the left-side air inlets.

Drying box with lid on top

Drying box with foam board lid on top, ready for drying session. This construction is fully light safe, and can be left for days in the light, if needed, without risk of fogging the paper.

- The air inlet: Drill four holes and use a saw to cut a square hole. To avoid weakening the tray to much, I have used two holes instead of one large one. Use the vacuum cleaner filters to cover them up and keep dust out, see the first picture above. Again use matting carton to create an effective light-block around the inlet, taking care to maintain free air flow.

Detail of air inlet

Detail of the air inlet. Note the vacuum cleaner filter covering up the inlet to keep dust out. Also note the protrusion on the outside of the tray. This is the light-block created using matting carton.

Detail of air outlet

Detail of the air outlet. Computer ventilators are hidden behind the drilled holes in this picture.

Detail of air outlet

Detail of the air outlet. Computer ventilators hidden in construction of light block, that uses two full U-turns to block out light and guide the air flow. Air flows out through the visible opening. Also notice the stacked coated papers inside the drying box.

Air outlet design

Cross-sectional view of air outlet and light-trap. Notice direction of air flow and also notice how the lid fits the tray.

- The lid. The lid is an important part as well, and must be light safe. Below is a detail of the lid. Notice foam strips and black matting carton is used to make it light safe. One full U-turn effectively blocks light. This is less than the two full U turns in the air in- and outlet, but remember the ventilators will effectively cause underpressure inside the box, sucking the lid on top of the tray!

Detail of lid

Detail of the lid of the box. Notice the black matting carton and foam strips used to create an effective light block. Also visible the 12V transformer powering the ventilators.

- The final part of the drying box are the glass plates. In the above pictures, you can see them stacked on top of each other, separated by the glued-on aluminium U beams. The U-beams effectively "interlock", keeping the glass plates from sliding on top of each other, ruining the coated papers.

You're done! Plug in the power and go! Since there is no heating, it will take several hours to half a day to dry the coatings, but excess water is effectively sucked out by the ventilators and it is a huge improvement over using paper boxes. To avoid buckling of papers that I intend to coat, I pre-soak and dry them on the glass plates using water-color tape before I effectively coat them. This will give perfectly flat coated papers. Especially these pre-soaked papers need a long (about 8-12 hours) drying time, while the emulsion coated papers, with much less water in them, will dry much quicker.