Darkbox Construction and Usage

Wet Plate Darkbox

Wet Plate Darkbox

The darkbox, it’s such a simple thing but so important. Wet Plates need to be coated, exposed and developed in a darkroom within 10 or so minutes, so unless you want to shoot plates in an area near your darkroom all the time, you’re going to need something mobile.

So how are you going to prepare and develop plates in full sun outside? Easy – a light proof box. Well, maybe not that easy. Let’s look at a few things we need to consider.

1. Light proof box. Even though plates are a little on the slow side (ISO 3 if you’re counting) you still need to prepare and develop them in the dark. And by dark I mean no outside light, the emulsion on a plate is orthochromatic which means it can’t see reds. That means we can use red light inside the darkroom and darkbox. There’s one problem with the lightfast-ness of a darkbox, it’s got a huge hole in it for the photographer. This is usually resolved by a few layers of material that wrap around the darkbox and then the photographer, bunched up to prevent light leaks.

Darkbox Design

Darkbox Design

2. Size. It’s a mobile darkroom, and while we’d love to incorporate an easy chair and a coffee table it’s just not practical for mobility. You want the smallest darkbox you can build while still being able to work inside. What size plates are coating in this darkbox? Will your trays fit? Silver bath? More importantly, will it fit in your car?

3. Ventilation. The smaller the box the quicker the chemical fumes can build up. You’re going to want a way to let those out a little quicker than just when you decide to leave the box.  Or you could just breathe them, but if you do that you’re probably going to have a bad time.

Design wise, I wanted a very basic box for my first design. Nothing fancy. Using Google Sketchup I came up with the design on the left which is pretty much a standard design. I’m using 3/4″ plywood for the first ‘prototype’, I’m not a fan of the look on the edges but it will be sanded and painted anyway. I’ll learn a lot from this build and will use different material next time.

Darkbox Side Design

Darkbox Side Design

So, with the main structure at 3/4″. I wanted to lighten the box as much as possible by adding 1/8″ plywood where I could get away with it. The sides and the back are the only places I could figure it would work. The top needs to be strong because of a carrying handle if and when I decide to add one. The sides need to be at least framed in thicker wood for stability and the bottom/front door needs to be thick for not only a sturdy work surface, but to take a hinge as well.

The basic measurement was drawn out and pieces made to fit. The sides were the most difficult part. I wanted a recessed lip on the inside for the 1/8″ plywood as well as notches to mate with the top and bottom for stability. Then I had to worry about a track for the 1/8″ plywood back to slide into the frame before I secured the top. To the right is the side design, note the four pieces and the tracks that must be cut into the wood. I could have cut this out of one piece of plywood, but I didn’t want to waste the wood. All joints are joined with 1/4″ dowels and wood glue.

Darkbox Side, on CNC Table

Darkbox Side, on CNC Table

And a shot of the CNC result. The parts are close enough to save wood but far enough away that they don’t decide to detach to the clamped down stock sheet of plywood and go boomerang-ing around the work area. Here you can see piece #1 in the back, #2 in the front and two sets of #3 and #4 in the middle. From the cut I would carefully saw the piece from the stock material, they use ‘bridges’ that are little un-cut tracks to keep the piece in place. Then it’s a sanding and assembly time.

Assembled, without doors

Assembled, without doors

Now that the sides are assembled it’s time to cut the top and bottom of the box. I don’t need anything on those pieces except a track for the back of the box. Everything is dry fitted and I move to building the back. I originally just cut the back with a rectangular hole for a piece of ruby red stained glass, but because I had some extra time I turned it into a slider. I even had a little round piece of Poplar that would work perfectly for a knob.

Now that everything is working together I glued the sides and the bottom. Small nails for stability, the box is getting painted anyway else I would have counter sunk them and used wood filler. The back is slid down into the frame and the top placed. Glued and nailed – everything lined up perfectly. At some point while I let the clamps do their thing I cut, placed and glued the 1/8″ plywood sides. Here you can also see the stained glass slider. It’s tight enough to keep out light without being too tight to slide open for ventilation when the plate is safe to come out of the darkbox.

Darkbox Back

Darkbox Back

Next doors were measured and compared to CAD (Sketchup) measurements. They were near perfect, those too were cut using the CNC machine because I wanted an ‘over/under’ lip so that the bottom door when attached would keep the top part of the door secure. This was best cut with the CNC machine. At the last minute these were fitted and attached with regular hinges on top and a piano hinge on the bottom.

Because I’d rather have an unpainted darkbox on legs than a painted darkbox on the ground, I moved to the folding table. The folding table is simple, scissoring legs with a base to sit the darkbox on. Before I go too far, be sure to factor in the absolute need of cross supports on the legs. They’re not pictured in the top design because I intended to add them later. In the future I will CNC the legs to take better fitted 2″ dowels. If you look at this closer view of my darkbox design you can see that the bottom of the box is actually up about 3/4″ from the sides. This is to create a notch in the table side bars so that the darkbox cannot shift left, right, forward or back! This design will certainly carry over to my next version as this worked perfectly in the field!

Darkbox on Table

Darkbox on Table

And here’s the darkbox on the table. You can see that we’re still unpainted and don’t have hinges yet, but its fitting absolutely perfectly. Everything was then disassembled and painted. The darkbox received a yellow paint job on the inside and an off-white paint job on the outside.

With this design I still attached guy lines to the box as my legs were a little unstable. The glue and nails on the cross bars wasn’t enough and they actually flexed at some point and decided to wobble. Thankfully I had already guy lined the box and there was no problem all weekend.

Everything else worked fine. I had plenty of room even though my working area is really 21 1/2″ wide and 7 3/4″ deep. The front door is 10″ so that’s additional work space. When you get a roll of paper towels in there, your upright silver bath, try trays and four chemical bottles it can get a little tight. Still though, I made quarter plates and could have easily made half plates in there as well.


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