Camera Obscura

Printing frame constructions materials

The knobs are applied to the structure of the frame and the spring, which are realized in tuliptree. It is a strong wood with compact fiber that guarantees a perfect dimensional stability and the maintaining of the square mount, even after months of strong pressures.

Printing frame structure is realized in tuliptree, the bottom –covered with black felt- in marine plywood of multi-layer pine-tree. Pressure knobs, closures and hinges are realized in steel.

Its bottom is realized in marine plywood of pine-tree. Multilayer, crossing the wood levels in different directions, guarantees the flatness of the bottom time after time, essential characteristic for a printing frame to compress paper in a uniform manner. The marine plywood, more than being water resistant, has better quality than the common multilayer.

Bottom, structure and springs are painted with several coats of wood preservative and finishes to guarantee the conservation of the printing layer and keeping the natural wood color.

The inner bottom part is covered with opaque black felt, to compensate paper and wood irregularities.

Hinges, quick closures and pressure knobs are realized in steel.

Pressure system of the printing frame

Pressure historically unites papers and negatives inside printing frames for contact printings and two or more springs ensure the compression of the bottom toward the structure. This system has several disadvantages:

• Even if springs offer a certain elasticity, it is not possible to significantly modificate the thickness of the print support. It is not possible, for example, to use the same printing frame to print on paper or on wood or glass plate.
• All of the materials loose elasticity as time goes by. Even steel made springs slowly adapt and take the shape due to the pressure. The printing frame gets less and less efficient. To obviate the problem, the majority of the printers add thickness between the bottom and the print with layers of materials such as felt, neoprene or even cardboard. Inspection from behind during exposition is therefore difficult or even impossible.
• Big printing frames need lots of springs to equally distribute the pressure points on the bottom. As a result the process to open the bottom part and position the print is long and difficult.

To obviate all of those drawbacks, I created an innovative pressure system that makes stronger, longer, finely adjustable and independent pressures that also adapt to support thickness. Everything is conjugated into a user friendly and a quick system of print opening and inspection.

Each one of the three panels of the bottom is compressed by a traverse with two pressure knobs, which means six total points of pressure on the bottom of the printing frame.

The pressure for each knob can be regulated independently and finely, turning a register of adjustments. The block-system keeps the chosen pressure level, without registering the pressure between two prints. The system has to be re-calibrated only when the support thickness substantially varies. It is also possible to print directly on the support itself only removing the bottom part, as when printing on thick materials such as wood.

Pressure knobs couples are mounted on traverses, hinged at one side of the structure and blocked by a quick jerky closure on the other side. It means that, once the pressure is okay, the printing frame can be opened and closed rapidly, working only on the three jerky openings that block the traverses.

Between the knob and the back bottom there’s a gum that compensates the pressure irregularities, similar to the classical spring conception. The huge advantage of the system is versatility that can be adapted to the most varied exigencies.

The system is projected to concentrate the pressure at the center of the image, leaving the problems for the borders, where there’s generally a white frame, without harming the print itself (using an A3+ negative format, the free margin measures some centimeters).

Finally, when it’s not used for ages, knobs can be easily unloaded, to have a minimum pressure that keeps the printing frame closed without stressing the structure to a long and intense pressure.

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