Observing the Lateral Etching

Cu_29_65_Gris_96Single or binocular loupes are often used to observe the effects of the etching on the surface of the copperplate. Depending on the kind of resin or screen used, it is sometimes difficult to view in detail what happens at this level. In some cases would be very useful to take a picture in order to compare or remind in the future. A fine device to do that is the ProScope MicroMobile from Bodelin Technologies (Fig., 1).

proscope_micromobile_iphone6s

Fig., 1. ProScope MicroMobile with the Apple iPhone 6s attached on top. (Click on the image to view an enlarged version. Image taken from Bodelin Technologies https://proscopedigital.com/product/proscope-micro-mobile-iphone-6-plus/)

The ProScope MicroMobile basic unit incorporates a lens system from Edmund Scientific with a magnification power from 20x to 80x, an adjustable LED illumination system, a built in desktop stand and a battery container with USB charger connection. Over this basic unit it can be attached a plastic sleeve suited for the given cellular phone or tablet. This lens system acts as a photomacrography converter for the cellular phone or tablet camera lens. If we want to use more than one device, we need to buy only one basic unit and as many sleeves as devices. The Fig., 2 shows the device taking a picture from a test target copperplate in order to determine how the plate is affected by the lateral etching for a given etching sequence.

proscop_iphone6s

Fig., 2. The ProScope microMobile assembly taking a picture from a test target plate. In the cellular phone screen can be observed the magnified image of the etched screen (click on the image for an enlarged view).

On top of flat surfaces, the ProScope MicroMobile can be used as an enlarging loupe, sharing with other people the viewing experience. This is very interesting in teaching purposes. Through the device camera, both still pictures or videos can be taken. This last utility is very interesting because when the image is viewed in a computer screen, it is enlarged again depending on the relationship in size between the camera phone pixels and the computer screen pixels. As an example, the Fig., 3 shows a picture taken with an Apple iPhone 6s camera through the ProScope MicroMobile. Viewing the image in the screen of a MacBook Pro Retina 15” laptop, the total magnification is of about 100x. With a non Retina computer screen, the total magnification is even higher. Such a magnification is not available without specialized and expensive devices (See Fotomacrografía for a better detailed explanation. I’m sorry, in spanish).

helio_91_screen900ppi_black_ink_scale

Fig., 3. Magnification of an inked an wiped plate showing a little area corresponding to a black surface (click on the image for an enlarged view).

In order to perform measurements from the pictures taken with such a device, there is an app, the ProScope QC, allowing to display an overlay with a measurement scale on the device screen. The overlay can be also incorporated to the registered image. The reference scales shown in the Fig., 3 and 4 have been incorporated by digital image processing after a calibration procedure. The Fig., 3 was taken from a plate black region after inking and wiping was completed. The Fig., 4 is the result after applying a threshold to the image in the Fig., 3. This binarization allows to measure which is the ink coverage after etching (and lateral etching). In the case of the example, a plate black area coming from a digital screen with a 45% of black coverage, results in an etched plate where the inked area covers a 65% of the total surface.

helio_91_screen900ppi_black_ink_autocontrast_thresholdisodata_scale

Fig., 4. Thresholded version of the image shown in the Fig., 3 (click on the image for an enlarged version).

Then, electronic devices and digital image processing software can help us understanding and measuring some practical phenomena. In this case, we have quantified the effect of the lateral etching for a given situation.

Posted in Early Photography, Heliogravure (english / français), Photographic Imaging, Photography, Photography Technique | Tagged , , , , , , , , , | Leave a comment

2016 / Bon Nadal – Merry Christmas – Joyeux Noël – Feliz Navidad / 2016

Week18_16Jun_22Jun_2014

Click on the image for a larger view

  • L’Hivern va dir: Això no és una imatge hivernal, el glaç s’està fonent. Això és a la Primavera.
    La Natura li va respondre: Exacte Hivern, però sense tu i el teu fred, la Primavera no podria fondre el glaç. Gaudeix de ser el que ets.
  • El Invierno dijo: Esto no es una imagen de invierno, el hielo se está fundiendo. Esto es en Primavera.
    La Naturaleza le respondió: Exacto Invierno, pero sin ti y tu frio, la Primavera no podria fundir el hielo. Disfruta de ser lo que eres.
  • The Winter said: This is not a winter picture, the ice is melting. This is Spring.
    The Nature answered: That’s right Winter, but without you and your cold, the Spring would cannot melt the ice. Enjoy of what you are.
  • L’Hiver dit: Ça c’est pas une image d’hiver, le glace est fondant. C’est le Printemps.
    La Nature lui répondue: C’est vraie Hiver. Mais sans toi et ton froid, le Printemps pourrait pas fondre le glace. Jouissez de ce que tu est.
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A Hybrid Approach to Photogravure on Copperplate

Cu_29_65_Gris_96The text and the images on this post have been published as an article in the Newsletter No4 (December 2016) from the Analogue Group of the Royal Photographic Society.

Reference/Citation: MITJÀ, Carles (2016) A hybrid approach to photogravure on copperplate. Analogue (4) pages 3 to 6. Bath: The Royal Photographic Society.

Photogravure was part of the early attempts made in the discovery of photography. Several previous experiments had been performed by Nicéphore Niépce and Henry Fox Talbot derived from the pre-existing gravure and etching techniques. Finally, after the first negative-positive systems appeared and responding to a problem with the permanence of his paper positives (Schaaf, 2003), Henry Fox Talbot patented the first photogravure method in 1852. Many years later, in 1879, the photographer and engraver Karel Klic modified the early Talbot method taking advantage of Joseph Swan’s and Louis de Poitevoin’s technique for the so-called carbon printing method. Klic’s decisive contributions were the aquatint grain on the copper plate and the use of gelatinised paper sensitised with potassium or ammonium bichromate, known as the carbon tissue. The result was called the Talbot-Klic method.

My interest in photogravure begun in 1985. I had seen some photogravure reproductions from the American photographer Jon Goodman in an issue of Camera from Switzerland (Goodman, 1981) and I became captivated by the description of the procedure. Looking for information, I discovered that several well-known photographers such as Edward S. Curtiss, Alvin Langdon Coburn, Alfred Stieglitz, Paul Strand and many more had been devoted to copy some of their images in photogravure. In his book The Printed Picture, the photographer, printer and teacher Richard Benson (2008) says, “…the [gravure] result could be more beautiful than anything else in photography”. Two years ago, being retired, I finally had the opportunity to explore this beautiful technique. After progressing through trial and error, I am now obtaining what I dare qualify as reasonable results. Beyond the complexity of the photographic part of the process, the photogravure encompasses an added difficulty since it requires skilled printing techniques. This elongates the learning process.

To produce a photogravure on copperplate, some materials need to be prepared as well as easy access to equipment. In first place, we need a system to obtain a positive transparency of the image to be etched. The original can be a photographic black-and-white slide or a high-quality inkjet printed version from a digital file. At present, I use an Epson R3000 printer with the Epson Ultrachrome Ink Set and the software of control QuadTone RIP printing on Pictorico OHP film (see suppliers).

Other items to be considered are:

  • Gelatinised paper, which can either be prepared by ourselves or bought. The two options still available today are Phoenix and Dragon Gravure from Cape Fear Press (see suppliers).
  • A yellow safelight free of UV radiation.
  • A solution of potassium bichromate (K2Cr2O7), 3% to 5% in water, the concentration affecting the contrast of the final print.
  • An aquatint box to grain the plates is also necessary. An alternative (and my current option) is a transparent screen of randomly distributed tiny points, digitally prepared in a computer and photographically printed on high contrast black-and-white film.
  • A vacuum contact press with a suitable ultraviolet (UV) lamp source (Mitjà, 2016a) to expose the carbon tissue both through the screen and the positive transparency.
  • Finally, we need all the usual materials and tools in an engraving workshop, for example:
    • Copperplates.
    • Trays for the several wet steps.
    • Ferric chloride (FeCl3) baths in different concentrations.
    • Etching inks, inking and wiping accessories.
    • Blotting paper.
    • Etching paper, and an etching press.

As an improvement to the traditional procedures, and taking advantage of a hybrid workflow, I use several digital techniques to contribute to the final quality of the photogravure on copperplate. The positives derived from digital files, both digital captures or scanned pictures on film, can be accurately processed in a computer to a level only achievable with difficulty by photochemical methods. After a given image is technical and aesthetically finished, digitally printed positives offer a direct control over the total density range by means of QuadTone RIP printer controller.

fig01_cmitja_ditherscreen

Figure 1. Digital screen created by diffusion dithering from a smooth medium gray image. The digital image is then printed on high contrast film by an imagesetter (click on the image to view an enlarged version).

However, probably the greatest contribution from digital techniques is the preparation of suitable digital screens. The digital screen (Fig. 1) ensures both a high resolution in the final print and a standardised method to graining the plates. A photomacrograph taken from a plate shows that its labyrinth scheme is accurately reproduced after the etching process (Fig. 2). Notice in particular, looking at the photomacrograph taken from the correspondent print, the geometrical pattern of the screen is completely lost when the ink passes to the paper under the etching press. The screen pattern merges with the paper fibres and is no longer present creating an even tonal shade .

Composite_CompleteScale_web

Figure 2. Photomacrography pictures comparing the screen (above), the etched plate (centre) and the printed paper (bottom) (click on the image to view an enlarged version).

fig03_cmitja_10steptesttarget

Figure 3. Grayscale Step Wedge to calibrate the method. The test is used to adjust the positive image Optical Density range, the UV exposure time and the digital image processing curve linearising the grey ramp (click on the image to view an enlarged version).

The calibration system also benefits from digital image techniques. The first thing to control is the total density range of the positive transparency. Then, a suitable test target (Fig. 3) is necessary to be printed with the same method used for the positive transparencies. The imprinted density range from black to white can only be reliably monitored with a transmission densitometer (Fig. 4). Suitable density range depends on the light source, the kind of carbon tissue, and the sensitiser concentration employed. The second question is to adjust the linearity of the grey tones in between the total test scale. Digitising the resulting test target in a final print allows readings to be taken of pixel grey level on the test patches. With these readings, it is not so difficult to build a software curve compensating the lack of linearity (Mitjà, 2016b). Finally, do not forget that a perfect linearly etched plate cannot provide a fine print by itself. The techniques of inking, plate wiping, paper dampening, and application of pressure in the etching press are decisive contributors to obtain a fine print beyond the simply correct one.

fig04_cmitja_densitometer

Figure 4. The densitometry of the printed test allows to fine tune the QuadToneRIP software in order to adjust the optimal Optical Density range (click on the image to view an enlarged version).

fig05_cmitja_uv_vacpress

Figure 5. Ultraviolet lamp with a distance adjusting system. On bottom, the vacuum press. The safety black curtains protect the operator from the hazardous radiations (click on the image to view an enlarged version).

In brief, the general procedure is as follows

  1. Prepare a perfectly polished and degreased copperplate.
  2. Prepare the monochrome positive image in the computer.
  3. Print it on a transparent media.
  4. Cut out a piece of carbon tissue of the same size as the plate and the positive.
  5. Sensitise the gelatinised paper by immersing it in a potassium bichromate solution.
  6. Stick the sensitised carbon tissue face down to a plexiglass plate bigger in size and let it dry.
  7. Expose the carbon tissue to the UV light through the digital screen (Fig. 5).
  8. Expose it again through the transparent positive. As a result, the lighter areas of the image generate a thicker hardened gelatine layer than the shadows.
  9. Stick the carbon tissue onto the copperplate, gelatine layer face down to the polished copper.
  10. Rinse the sandwich in hot water (≈50ºC). Remove the base paper and wash out all the non-hardened gelatine. There is now a gelatine layer on the copperplate whose difference in thickness is related to the image tonal values.
  11. Etch the plate in a succession of ferric chloride baths with decreasing concentration, looking at the progression of the etching in the different tonal areas of the image.
  12. Wash and dry the etched plate.
  13. Ink and wipe the plate as is usual in printing practice (Fig. 6).
  14. Pass the inked plate in contact with a wet paper under the cylinders of an etching press (Fig. 7).
  15. Allow the inked paper to dry (Fig. 8).
fig06_cmitja_plateink

Figure 6. The plate is inked with a brayer and wiped with the so called tarlatan cloth (click on the image to view an enlarged version).

fig07_cmitja_etchingpress

Figure 7. The inked plate and a dampened paper are passed through the cylinders of an etching press (click on the image to view an enlarged version).

Finally, why do photogravure? Although it is a difficult and long path, if all steps are correctly applied, a photogravure print shows a complete tonal range image with subtle lights, smooth transitions and dense blacks. A sense of thickness is clearly perceived, especially with classic oil-based etching inks. A photogravure print looks more like an object than a flat sheet of paper. In these days of digital imaging, photogravure as a final art rewards the digital file with a physical, tangible and long-lasting expectancy. It combines the advantages of nowadays technology with the sensitivity of hand crafted things.

fig08_cmitja_print

Figure 8. The final print on a high quality paper shows the characteristic plate embossing (click on the image to view an enlarged version).

Several examples of prints made with the described method can be seen at: https://carlesmitja.net/2016/10/08/heliogravure-gallery-cityscapes/ , https://carlesmitja.net/2016/02/24/heliogravure-gallery/ and https://carlesmitja.net/2017/03/25/heliogravure-gallery-landscape/

References

Bibliography

  • Blaney, H. R. (1895) Photogravure. Ed. The Scovill & Adams Company, New York.
  • Cartwright, H. M. FRPS (1930) Photogravure. American Photographic Publishing Co., Boston, Massachusetts.
  • Cartwright, H. M. FRPS (1961) Ilford Graphic Arts Manual Vol1, Photoengraving. Ilford Limited, Ilford, Essex.
  • Denison, H. FRPS (1895) A Treatise on Photogravure. Ed. Iliffe & Son, London.
  • Morrish, D. (2003) Copper Plate Photogravure, Demystifying the Process. Focal Press, New York.
  • Reeder, R. (2010) Digital Negatives for Palladium and other Alternative Processes. Ron Reeder.
  • Saff, D., Sacilotto, D. (1978) Printmaking. Harcourt Brace Jovanovich College Publishers, Orlando, Florida.
  • Sacilotto, D. (1982) Photographic Printmaking Techniques. Watson-Guptill Publications, New York.

Suppliers

Posted in Early Photography, Heliogravure (english / français), Photography Technique | Tagged , , , , , , , , , | 3 Comments

Tower of Babel

Cu_29_65_Gris_96

Some days ago its been a discussion in Facebook about the correct word defining different printing techniques. It is a periodically recurrent discussion about the correct word to name a photogravure print, depending on the way it was generated. A paragraph in the discussion said: “… referred to her etchings as engravings–a much different technique.”

Being interested in printmaking and also in the correct use of language, I have performed some search. If we take the former phrase and ask Google Translate on how it translates in several languages, the answers are:

  • Original in english: …referred to her etchings as engravings–a much different technique.
    • Spanish translation: … que se refiere a sus grabados como grabados – una técnica muy diferente.
    • French translation: … appelé ses gravures comme des gravures – une technique très différente.
    • German translation: … Bezogen auf ihre Radierungen als Gravuren – eine viel andere Technik.
    • Italian translation: … cui ai suoi incisioni come incisioni – una tecnica molto diversa.

Note that the three Romanesque languages, do not establish any difference between the english etching and engraving words. Only in German there are two different words. But if we take several dictionaries, the answers are somewhat different and confusing. It is well known that translators like Google establish its answers taking data from dictionaries and also from contextual phrases and/or key words tagged in Internet contents. Then, those translations can often obey to a habitual use of language, better than a correct use of language.

Following with my exercise, I searched in my e-mail. On February 2015, I asked Jennifer Page from Cape Fear Press about how to name a technique with photo-polymer film Puretch used as a resist on copperplate. In her answer he wrote:

  • “In regards to what this etching process is you are doing with Puretch, we call that Photo Etching. I suspect when translating Photo Etching to Spanish the terminology may be somewhat similar to the translation for Photogravure. The problem is when people using photopolymer plates call it Photogravure instead of photopolymer intaglio.”
  • “… Photogravure (gelatin resists), Photo Etching (Puretch) and Polymer Intaglio (Solarplate, Imagon and Toyobo).”

Note that in the first paragraph, Jennifer uses a preventive “we call”, very wise on her part. She also refers to the possible confusion between the English etching and gravure when they are translated to Romanesque languages, as we have already seen in the earlier list of translations. In the second paragraph, she makes an statement about how to call each particular technique. Taking again those definitions in Google Translator, the results are even more confusing than in the early list.

  • English: etching, intaglio, gravure
    • Spanish translation:
      • aguafuerte, huecograbado, huecograbado.
      • ————–, calcografía, huecograbado.
    • French translation:
      • gravure, héliogravure, héliogravure.
      • ———-, en creux, gravure.
      • ———-, en taille douce, ———-.
    • German translation:
      • Ätzen, Tiefdruck, Tiefdruck (no options)
    • Italian translation:
      • incisione, intaglio, rotocalco.
      • acquaforte, calcografica, gravure.

As can be seen in the list, not only there is some difficulty to distinguish between some English words when they are translated to Romanesque languages, but there are also some options not always clear in its conceptual meaning. Even considering that Google translations are more colloquial than normative, the labyrinth is there and it is not so easy to scape.

confusion_of_tongues

Engraving The Confusion of Tongues by Gustave Doré (1865). (Gustave Doré [Public domain], via Wikimedia Commons)

The words heliogravure and photogravure are also used in some areas to distinguish between the classic hand made technique and the industrial printing process, respectively. Also in France is usual to specify héliogravure au grain, referring to the use of a powder aquatint, while if it is not specified, it can be referred both to the use of powder aquatint or analogue and digital screens.

Even taking the classic bibliography, there is not so difficult to find some confusing definitions. Most recently, we can found two Facebook groups which respective names try to establish a distinction. The Copperplate Photogravure group states it is a space of “Discussion of Copperplate Photogravure issues and technique”. Entering the group discussion, the only technique considered is the classic Talbot-Klic , both with powder aquatint or analogue and digital screens. The other group, Photogravure, announces “This group is for sharing techniques, materials and images created using photopolymer and traditional copper plate photogravure.”

The group Photogravure entitled with this word both techniques, qualifying of photo-polymer or traditional copper plate to distinguish between them. But there is no reference separating photo-polymer film used as a resist on copperplate from photo-polymer commercial plates or Imagon thick film. A bit confusing again.

Then, my opinion is that the correct use of the language is very important, both by a simple matter of correction and also for improved communication. The problem is that with this lack in agreement, it is also difficult to say where or when it is appropriate to use each word. On the understanding that this does not excuse those who try to hide the true technique with which an impression has been made.

I’m wondering that in the past, with probably a lot of practitioners but poorly communicated, all that was not so important. Nowadays, with a lot of communication possibilities, it is likely more important than ever to establish some kind of standardization about the names of techniques, specially attending to the differences between english an Romanesque languages. Even taking into account a global view better than a particular use in each region or language. A new (old) theme to discuss.

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Heliogravure Gallery – Cityscapes

This gallery contains 6 photos.

Gallery with reproductions of heliogravure prints from urban landscape. The images have been engraved using bichromated gelatin as a resist over a copperplate. All prints are hand inked and wiped, then pulled in an etching press. In the Slide Show, … Continue reading

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