The polymer photogravure process is a photo-mechanical printing process that turns a photographic image into a crafted object. It combines modern digital imaging techniques with the very traditional intaglio printing process.
In fact photogravure is one of the earliest photographic processes – developed in the 19th century by the pioneers of photography – you can read about it here https://photogravure.com/story-of-photogravure. Traditionally it was done using copper plates that were etched using acid from which the plate was variably protected using a light sensitive resist material. For some the traditional technique is the only ‘true’ photogravure process. However it is technically challenging, uses some quite unpleasant chemicals and the plates it produces have a limited lifespan due to the soft compressible nature of copper.
Today we have an alternative solution which preserves many of the creative opportunities afforded by the traditional technique but dispenses with the chemicals and results in a printing plate with excellent tonal range that delivers consistent prints time and again – polymer photogravure – which uses a steel plate coated with a UV light sensitive polymer which once exposed to the image is then etched simply by washing in water.
Notwithstanding this, polymer photogravure is an involved technique that requires investment in time, skills and equipment. It is the antidote to the quick and soulless photographic prints produced by online photo-labs or ejected from your inkjet printer. I will take you through the steps required to produce a print or print series – the purpose I hope is to inspire you. However if you do decide you would like to try this technique I would highly recommend you read more widely (Clay Harmon’s ‘Polymer Photogravure‘ guide is a good starting point) and also attend a course of which there are a few around the UK (I attended the excellent course at Lux Darkroom by Constanza Isaza in Islington London)
Step 1 : The Source Image
First of all to note – polymer photogravure is a monochrome technique. That’s not to say it is colourless as there are ways and means of adding colour to your image. It is even possible to do CMYK multi-pass prints using the technique giving full colour images. These are all advanced techniques – way beyond me at this point in time.
So your starting point is a black and white image. Selecting an image that will respond well to the process is important. The printing process uses traditional intaglio printing inks – one of their strengths is that they are fabulously opaque – the blacks are very black and this has a tendency to result in quite contrasty prints, its really important to work on bringing out the mid-tones of your image. Secondly until you are quite practiced at the technique you are likely to produce a degree of random tonal variation from your inking technique – this is a good thing as it is one of the ways of bringing about creative input to the process and means every print is a unique work of art. However what it does mean is that you don’t want to be starting off with images that have large areas of flat mid-tone – so a picture with texture and tonal variation is a good starting point.
This photo of a tree stump at the bottom of a waterfall is a good example – it has a good tonal range and a lot of texture – the variations of which form the composition (the falling water in the background, the flowing water in the middle distance and the craggy tree stump in the foreground. It is important that your starting image makes full use of the grayscale tonal range – I will talk about black and white conversion and grayscale optimisation in a future blog.
This particular source image is digital – taken on my Fujifilm XT30 on holiday last year. You can use any image source you like – even pictures taken on your phone. My particular favourite source though is analogue film – many of my photogravures originate from pictures I take with my medium format Bronica ETRS on to Ilford HP5 film. The film adds a gorgeous texture to the final print. Follow this link to see my analogue to digital conversion method.
Step 2: Producing the transparency
The next step in the process is to create a transparency with which to expose your polymer plate. The polymer on the plate is hardened by exposure to UV light – this means the less exposed parts of the plate are washed away creating craters that hold the ink (printing shadows) and the exposed parts create islands that hold less ink (printing highlights). It is therefore a positive to positive exposure technique (unlike most other alternative photography techniques that require a digital negative).
The other important thing to note is that the plate’s sensitivity to UV light is not linear across the grayscale tonal range. This requires a quite involved calibration process to find both the correct exposure time and also an adjustment curve to apply to the image in order to ‘compress’ to the tonal range of the image into the sensitivity range of the plate. The details of the calibration process warrant a whole tutorial of its own – a future blog.
Once you have applied your adjustment curve (the output of your calibration process) to your image you can print this onto inkjet transparency material – I use Pictorio Ultra-Premium Transparency film – which is designed for use with inkjet printers. The result is a quite dark and flat image which on the face of it does no justice to your original image – but don’t worry, trust the process!
Note also that I have colorised the image – this is because some colours actually absorb the UV light better than black ink – again there is a process for identifying the optimum colour with which to create your transparency.
Step 3: Exposing the plate
For this step you need two things – some polymer plates (I use Toyobo KM73 – which can be bought from printing supplies shops) – and a UV exposure unit. Again you can buy UV exposure units – but I decided to build my own – I will show you how in a future blog.
There are two stages in the exposure. The first stage is to expose the plate to an ‘Aquatint Screen’ – this is a screen of very fine dots which adds a ‘texture’ to the polymer. The texture is required to hold the ink in the craters of the image – a bit like a sponge. You then expose the image itself – its very important that the transparency and the plate are very tightly held against each other. The preferred way of doing this for many photogravurists is to use a vacuum frame. However I have opted to use a sheet of safety glass in a kind of giant flower press arrangement.
The nice thing about this process is that the plates are not that sensitive to visible light so you don’t need a dark room – although you should avoid direct sunlight and florescent tube lights. Here’s my homemade UV exposure unit:
Step 4: Develop the plate
This is done in water – I use a developing tray and make sure the water is at precisely 20 degrees centigrade using an infrared laser thermometer – place the plate in the water – allow it to develop undisturbed for 1 minute and then gently ‘scrub’ the plate with a soft brush for a further 2 minutes. The plate then needs to be rapidly dried – I use a super absorbent e-cloth to remove excess water followed by 3 minutes of drying with a hairdryer on full.
The plate is now developed but the polymer is still quite soft and can be easily damaged so now needs a further period of direct exposure to the UV light to ‘harden off’ the polymer engraving.
You now have a plate with the relief of your image engraved on its surface ready to start printing!
Step 5: Inking the plate
A number of tools required at this stage:
- A magnetic mat to hold the plate firmly whilst inking up the plate
- A soft plastic spatula to spread the ink
- Tarlatan cloth (also known as scrim) to remove the excess ink from the plate
- Tissue paper to polish the highlights of the image
- Soft muslin cloth to clean the edges of the plate
- Its wise to wear thin nitrile gloves as well
There are any number of inks out there – but the most popular brand is Charbonnel and I use their Black 55981 mixed with a little Burnt Sienna. But you can experiment away with different colours and shades of black.
Inking technique is the subject of much discussion and variance amongst artists – suffice to say this is where getting some tuition is a good place to start and from there develop your own style.
Step 6: Printing
Two pre-requisites for this – paper and a printing press! Choosing paper is quite daunting at first – there are so many to choose from all with different qualities, strengths and weaknesses (and prices!). My advice is choose something simple and stick with it for a while whilst you develop your technique. I am using Fabriano Rosapina which is a lovely quality Italian brand of paper suitable for intaglio printing – not excessively expensive and widely available.
And then there is the press – this is by far the biggest investment you will make if you are going to start doing this sort of printing. The common advice is to sign up with a local print maker’s collective – of which there are many around the country – and take advantage of both the equipment and the experience of the group. Unfortunately for me ‘local’ meant no less than 40 miles away – so after much research I invested in the Ironbridge Printmakers ‘Gunning Press No.1‘. Here’s mine:
As you can see – it takes up quite a bit of space – this is the largest of their ‘table top’ range, next size up requires a stand of its own. This will print on paper up to 15″ wide and 29″ long. Learning to use a press is probably the other aspect of this whole process for which it is worth investing in expert tutelage.
The paper must be prepared before printing – this requires it to be soaked in water for at least 20 minutes – and then pressed by hand between sheets of blotting paper to achieve a ‘just damp’ state. The inked up plate is placed on the registration bed, followed by the paper, followed by a sheet of plain ‘newsprint paper’ (aka fish&chip paper!) then the blankets of the press are laid over this. The press roller is tightened and then the whole sandwich is passed through the rollers – this requires some effort, the rollers are applying an enormous pressure onto the paper and the plate in order to squeeze the ink deep into the fibres of the paper.
Step 7: The Reveal
The final step is to peel back the layers of the sandwich and very very carefully lift the paper away from the plate. The paper, after its soaking, is very soft and can be very easily damaged so great care is needed. Flip your print onto a neat bed of newsprint – inspect it (enjoy the thrill of seeing the results of your labour), allow it to air dry for a bit before placing a protective sheet of tissue paper over the image and then placing the whole print under layers of newsprint and a flat heavy weight to leave it to dry for about 3 or 4 days (yes that long!). Doing so means the paper will dry absolutely flat.
You can see that the image nestles within the emboss that the plate creates on the paper. The transfer of ink from plate to paper is complete, creating deep satisfying blacks and the dynamic tonal range of the image has been restored. The paper itself becomes part of the visual experience, it’s texture, colour, shape and deckled edges – which is why my preferred display method is to ‘float mount’ the print within a box frame.
This is – above all – the noblest destiny for a great photograph!