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Preparation, Exposure and Development of ImagOn-HD Polymer Film |
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Preparing the ImagOn |
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ImagOn film consists of a photosensitive polymer emulsion sandwiched between protective layers of acetate.
The ImagOn emulsion may be bonded to almost any flat non-greasy surface. For printing with an etching press the choice of support includes thin sheets of copper, zinc, perspex, MDF (Medium Density Fibre) board and any similar material. If the surface is not completely flat and dust-free the film will not adhere to the imperfections on the surface. The material should be degreased either by chemical means, or by mechanical means such as sanding with a fine carborundum paper.
The film should be opened under subdued lighting and cut to size allowing a slight overhang on all sides of the intended support material. Identify and remove the thinner of the two plastic coverings by carefully peeling it away from the sheet. For the ImagOn the following method was used which, might also work for ImagOn: first, peel off the top mylar layer. For this use a piece of double sided scotch tape, that is stuck on to a table corner. Stick a corner of the film on to the tape and try to peel off the emulsion layer while the top mylar sticks to the tape. |
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Bonding the emulsion to the support (ImagOn) with help of an etching press |
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A press, set to a reasonably firm pressure, is used to affix the ImagOn polymer emulsion to the support plate. An etching press with a perfectly flat bed is recommended. If the bed shows any inconsistencies a thick sheet of perspex, or similarly unblemished material, should be laid over the bed.
Place the ImagOn film (emulsion side up) on the bed of the press and lay the support plate over it. To prevent sticking to blankets the discarded protective layer may be placed over this arrangement before pressing. The polymer emulsion is adhered to the plate by running it through the press at a slow and steady speed of approx 12 feet per minute. It is worthwhile also to experiment using the "squeegee-method" to affix the emulsion to the plate. |
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Bonding the emulsion to the support (ImagOn) with help of a squeegee |
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The "squeegee-method" is introduced for the ImagOn film. First, peel off the inner mylar layer. For this use a piece of double sided scotch tape, that is stuck on to a table corner. Stick a corner of the film on to the tape and try to peel off the emulsion layer while the inner mylar sticks to the tape. Spray some water on a clean copper plate and place the film gently on it. Now start squeegeeing from the center to the edges, thus removing spots of air between the film and the plate. Try this also for the ImagOn film. |
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Trimming the plate |
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With the emulsion firmly bonded to the support plate use a sharp knife to trim the overhanging film back to the edges of the plate. To ensure a clean edge it is important to trim from the film side. |
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A suitable positive |
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A transparent positive image is required for the exposure. This may be hand drawn onto mylar or tracing paper; prepared photographically in the darkroom, or photocopied to transparent acetate from a original source image |
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Aquatint screen exposure |
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(This step may be omitted for line work with no areas of solid black)
If the image contains a range of tones, or areas of solid black, it is necessary to perform a pre-exposure of the ImagOn using an aquatint (or mezzotint) screen. The plate should be set up in an exposure frame such that light from the source passes through the screen before reaching the emulsion on the plate. A short exposure is made before removing the aquatint screen and inserting the positive in its place.
The plate is seen here as if looking down onto a glass table exposure frame - the aquatint screen is located between the glass and the plate. |
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The main exposure |
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The main exposure is made with the light passing through the positive directly onto the emulsion on the plate. An exposure time of 12 seconds at a distance of 1 metre is recommended as an average. The actual exposure time will vary depending upon the type of light source and the nature of the positive image.
The plate is seen here as if looking down onto a glass table exposure frame - the positive (face upwards) is located between the glass and the plate. |
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Ghost image after exposure |
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A correctly exposed plate should show a ghost impression of the image on the emulsion when it is removed from the exposure frame. |
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Preparing the developer |
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The emulsion is developed in a tray of Soda Ash solution. This should be mixed at approx 1 teaspoon of Soda Ash per litre of water. The correct measure of crystals should be dissolved in a small amount of warm water which is then made up to the correct strength by adding cool water. |
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Peeling away the final layer |
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Before placing the plate in the developer it is essential to remove the protective acetate film from the now-exposed emulsion. Lift one corner gently, taking care not to lift the emulsion with it, and peel it back to reveal the surface of the emulsion. |
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Developing the image |
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The plate is placed face up in a tray of developer and gently swabbed with a soft sponge. Over the space of about 2 minutes all unexposed areas of the emulsion should wash away, revealing the plate as image. |
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The developed plate |
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The fully developed plate showing all unexposed areas washed back to the support plate. |
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Rinsing off |
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After development is completed the plate should be thoroughly rinsed with clean water and squeegeed dry. |
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Squeegee dry |
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Squeegeeing the plate assists in speeding the drying time, ensuring the emulsion does not soften while wet. |
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Final hardening |
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The plate should be hardened by exposure to direct sunlight for twenty minutes to half an hour prior to use. In the absence of sunlight an alternative heat source may be used.
The plate is now ready to print. |
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