Arrigo Mamone shows an alternative working method in heliography, preparing his own pigment paper.
Always be careful when handling chemicals. Read the health and safety instructions.
Heliogravure, or photogravure, is one of the most sophisticated photo-mechanical processes, and an intaglio printmaking process (other methods are offset, rotogravure and photo etching). Images are printed by making printing plates, then transferring the image onto paper.
Heliogravure is a photographic printing process made up of two steps:
- A Photochemical process that creates the intaglio surface where the photographic image is etched into a copper plate.
- The copper plate is used to print the image onto etching paper using inks.
It is good to use a good quality thick paper, that can draw out the ink from the recesses of the copper plate.
Arrigo’s method is a little different from others. He transfers the tissue paper onto the plate BEFORE graining, rather than after. This makes it easier to grasp the plate. Let us see what he does:
Heliogravure: The transfer and the graining
To conduct the classical heliogravure au grain process you have to prepare a proper positive film of the same size as the final print, containing the image that is to be transferred on a copper plate. For the purpose, use a special pigmented jelly paper (tissue paper) previously sensitized and exposed to a UV light under the positive film. After the transfer, the plate will be etched with different densities of Iron (III) chloride baths.
The transfer part begins with preparing a perfectly smooth and polished copper plate(1).
After that operation, every text on heliogravure says that you should first, "powder" the dry and clean plate in a dust box – the same way as in aquatint etching method – and melt the bitumen dust on a heating source, to obtain the "grained" surface – or the ground as it is called). Second, to dip the plate into a cold water tray and THEN make the coupling with the exposed pigment paper – soaked in the same container – let it stick on "the ground" and peel off the paper.
This operation, shortly described here, is very delicate because you have to convince a jelly layer swollen with water, carrying your masterpiece, to stick totally and free of tensions, to the tough and rough grained metal leaving the pliable paper where it originally stands. That is why the metal must be perfectly clean and free of grease and dust.
I always found it rather difficult and unsafe to do in this way
because the grasp of the wet jelly on the bituminised surface remain uncertain even after an accurate pickling and personally had several bubbles and raising of the jelly film during the following drying.
"The ground" is more rough than smooth and the same single bitumen grain on it is not hydrophilic, making the operation even more critical.
For this reason I tried to turn over the transfer of the jelly doing it BEFORE the graining of the plate, with good results. This is how:
1Transfer the jelly
First I transfer the jelly: dipping the perfectly polished copper side and the exposed tissue paper face to face into the same tray of filtered cold water, I couple the two underwater; roll carefully to squeeze air bubbles and excess of water, and keep pressed the sandwich for several minutes out of the vessel; dive again the couple into warm water and peel away the paper leaving the jelly image on the smooth plate surface. Then I finish the "developing" (which is really a stripping) to eliminate the unexposed jelly plus pigment and let it dry completely at room temperature (2). These operations anyway seem simple but demand good handling.
2Graining the plate
Second I grain the plate: Before inserting the plate with the dry jelly image into the dust box, I warm it from the back with a hairdryer to be sure there are no traces of humidity, avoiding tensions on the jelly.
In the time the plate is dusting, I warm a suitable thermostatic oven to 50°C (3) and when I carefully put the "powdered" plate inside, I let it a couple of minutes with the lowered cover before switching the heating on again.
In this way the shrinking of the jelly layer is uniform on the copper and – unbelievably – does not crack (9.5 over 10 !) at 120 – 130°C of bitumen melting temperature, but hardens on the copper.
The melting time is fixed so I do not need to check but just put a bell’s timer on.
When finished most important is to let the plate cool slowly (5-10 minutes), raising of a little extent the cover of the oven.
The self-made oven is conceived as a flat and large square box – according to the maximum plate’s size – of refractory material (thin fire bricks at the bottom – on a glass wool bed – and sides), an insulated electrical serpentine covering the inside base, a 3 millimetre aluminium plate raised from the serpentine as heat diffuser and over it an adjustable metallic frame where to "suspend" the plate – so it can receive uniform heating at a chosen speed.
An insulating cover filled with glass wool close the oven. All the inner surfaces are in thin aluminium foil (mirror-like to reflect the heat) and a probe inside the oven tells constantly the inner temperature to an outside display. The thermostat - with a proper probe inside the oven – is fixed, after trials, at the correct temperature for melting.
As you see from the pictures I enclosed, the outside frame in contact with the outer side of the firebricks is wood; it may appear hazardous, but the temperature of the external side of the bricks does not reach 50°C at the maximum.
- The plate is polished with emery paste or paper or with individual chemical methods, and pickled using "Medoun white" or "Spanish white" powders (i.e. soft carbonates, degreasing and not abrasive) in such a way that after these operations, the tap water run all over the surface without leaving "spots" in any part of it.
- I recover all the resulting polluted liquid and put it in an open air evaporating container to concentrate. Do not discard into the sink!
- To win the thermal inertia of the great mass of the oven itself and to permit an equilibrium medium temperature all over the inner volume.