Unformatted text preview: Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. FILM PROCESSING
The Stages of Film Processing
Development This process reduces the exposed silver to a visible molecular silver. Developer is an alkaline substance containing: Developing agent (D.A) - Hydroquinone most important element in developer Reduces the exposed silver to a visible moluecular silver Restrainer - Bromide Holds back the D.A. so it doesn't affect unexposed area Anti-oxidant (Buffer) - Sulfide Prevents D.A. from reacting with air
Exposed silver turns to black Stop Bath(Optional) This process stops the developing action by passing the film through a solution of Acetic Acid
stops silver turning into black Fix This process removes the unexposed silver from the film. Fix contains a solution composed of Sodium Thiosulphate Wash The film is passed through a tank of fresh water to remove any remaining chemicals etc. Dry The film is dried before handling.
CGRA 013 - INTRODUCTION TO ELECTRONIC PREPRESS Page 1 of 5 Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. Variables that affect development
Temperature For every + 1 F change in temperature there is a 10% temperature higher = faster process increase in development action Strength Processing film depletes D.A. takes away strength Aerobic Deterioration: Oxidation depletes Buffer and D.A. of developer Anaerobic Deterioration: Components of developer interact and attack the D.A. in "Lith" systems 'Replenishment' is necessary Time The longer the development time, the more it develops
control amount of developer by speed of processing becomes blacker and blacker Agitation More agitation increases development & contrast Hydroquinone ("Lith") developer
The first "machine processing" chemicals Difficult to control - required constant monitoring - running of 'control strips' (pre exposed grey wedge that should result in specific density readings) - 2 & 3 part "replenishers" added to keep chemicals at the required strength CGRA 013 - INTRODUCTION TO ELECTRONIC PREPRESS Page 2 of 5 Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. Processor Scheamtic developer recycles and gets agitation, controls temp Machine Processing Processor control of variables: Temperature Recirculated developer passed through a heater and cooling unit to control the temperature Agitation Pump circulates the developer providing agitation Strength Developer Replenisher compensates for exhausted developer due to film processing, aerobic and anaerobic deterioration. Overflows keep the developer, fix, and wash levels consistent when replenishment triggered. Roller Speed Controls developer time
CGRA 013 - INTRODUCTION TO ELECTRONIC PREPRESS Page 3 of 5 Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. Effluents and Silver Recovery
- Silver is a "Heavy Metal" and a pollutant. - It is released into the fix when processing. - It is a valuable recoverable metal. of - The cost of waste chemical disposal - $70.00 per 10L Developer or Fix.
- remove silver from fix before it goes into drain Silver can be recovered by various methods: Metalic replacement: - a metal lower on the activity table (iron - "steel wool") replaces the silver in solution when it is run through the unit. Electrolytic replacement: - a current is passed through the fix solution and the silver is attracted to the cathode, "plating" onto it. In some Photo Finishing systems the fix can then be reused. There are other by-products ("Sludge") that should be removed from the effluent prior to passing it to the drain. Some areas of the US have a zero tolerance to effluent and all chemicals must be captured and disposed through a licensed disposal company ($70 per 10 Litres).
30% of silver is in the wash water. check wash water also
CGRA 013 - INTRODUCTION TO ELECTRONIC PREPRESS Page 4 of 5 Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. Electrolytic Recovery Cartridge
From Fix & Wash overflow Anode To drain Cathode (Silver plates) Our Chemical Treatment
In our system the fix and wash overflows are both connected to a silver recovery unit. Waste silver is attracted and clings to a cathode when electrical current is passed through the fix. This waste silver is recycled. All Effluents from our processors including the developer are then passes through a filtering sytem to be treated. Future EPA rules may include a zero effluent law in Toronto. Presently, the law only calls for the removal of heavy metals and sludge. Our system excedes the presend legislation.
CGRA 013 - INTRODUCTION TO ELECTRONIC PREPRESS Page 5 of 5 Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. Different types of Processors
Lith processors Development time: 90 sec Temperature: 80 F Developer activity has to be critically controlled (control strips) Very high quality Rapid Access processors Development time: 15 sec Temperature: 105 F Developer activity extremely stable (no control strips) Lower Contrast Halftone & Line quality suffer Hybrid Systems E.g. Fuji Grandex Best of Lith & Rapid Access- quality, stability, fast processing Alternative Systems
Stabilization Products (Dated technology) Developer incorporated products steps include: - Activate, stabilize, fix, wash, dry high cost of films, short developer life, quality? Lower Capital investment, speed
CGRA 013 - INTRODUCTION TO ELECTRONIC PREPRESS Page 6 of 5 Edited by Foxit Reader Copyright(C) by Foxit Software Company,2005-2007 For Evaluation Only. Silverless Products Xerox Verda - discontinued Polariod - Thermal Polymer Emulsion - diffusion transfer , no "wet" processing Kodak - Thermal Polymer - non fused emulsion powder vacuumed off film surface. This technology is also used for Polyeste CTP Plates. Note: The cost of investment and R&D must be weighed against usefulness (Product life?). How long until CTP is dominant? Both Kodak and Fuji suggest that film sales peaked in 2000 and have declined slowly for the last 3 years. However, rapid decline in total film sales is anticipated in future. As of 1998, CTP accounted for less than 7% of the total plate market. Today, 30% to 40%.................60% - hard to calculate. - larger printers are using CtP exclusively (Quebecor & TCP) - smaller printers are slower to convert ( less than 3% saving in production costs for CtP compared to full imposed film output) Film will be with us for the next 10 to 15 years
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This note was uploaded on 04/21/2008 for the course GCM GRA203 taught by Professor Goodyear during the Winter '08 term at Ryerson.
- Winter '08