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Printech, August, 2000
Re: reducers and intensifiers


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From:GaryJGATF(gjonesprinting@aol.com)
Date:Tue, 29 Aug 2000 12:56:47 EDT


Sherry: In response to your questions: 1. Reducers and intensifiers are generally used on film negatives and not plates to adjust the image. They are either used on a selected area or on the entire film negative. They are not used in conjunction with the other film development chemistry or processors, so there should be no intermingling of the chemistries. With respect to the classification of solutions used for reducing or intensifying as to being hazardous or not, they would have to be evaluated under the definitions of characteristic wastes and perhaps tested using TCLP. 2. Ammonium thiosulfate is present as a critical ingredient in fix as the thiosulfate is used to remove the silver from the film. Printers do not add ammonium thiosulfate to the fix as suggested by all of the P2 books. Its sounds appealing in theory, but is not practical. The first real challenge that the P2 books don't tell you is how much is to be added? How much is a practical limit? In other words, can I continue to add it? When do I know to add it in the first place? Also, where is the printer expected to purchase the chemical? How much does it cost and is it cost effective to do this. If a printer would happen to add the chemical and there is problems with the film, the film and chemistry supplier will not stand behind their products because the printer decided to play chemist. Lastly, using this chemical will cause more silver to enter the environment as a small portion of the fix is carried over into the washwater and the washwater is typically not passed through a silver recovery unit. Therefore, if the fix contains a higher level of silver, then more silver enters the environment. 3. For almost the same practical limitations as stated in #2, acetic acid is not used to extend the life of the fixer. The best approach to extend the life of the bath is use a fixer recycler with a silver recovery system or switch to the new chemistries that require replenishment on a less frequent basis. 4. I think Fuji is the only company offering a hydroquinone free developer. I will check with Kodak and Agfa. 5. The differences between the plate terms you mentioned lie in the plate base materials and the plate imaging material. The most common plate base materials are paper, plastic, and aluminum. These base materials are then coated with a light sensitive material. If the plate comes precoated with the light sensitive material then it is said to be presensitized as opposed to one that is considered a "wipe on" where the image material is applied by the printer. Most printers use presensitized due to plate life and quality control concerns. Photopolymer refers to one type of light sensitive coating that is used on a plate. The plate is imaged with UV light to harden the polymer and the unimaged area is washed off the plate. Some of the newer direct to plate systems use heat and not light to image the plates and these plates are called thermal plates. Aqueous plates refers to the chemistry used to process the plates to remove the unimaged portion of the light sensitive coating. Most of the new direct to plate and existing conventional plates are developed with aqueous systems. Waterless plates require solvents and other newer plate technologies (ink jet and thermal) require no or minimal processing. There are no books that are dedicated to covering all of the plate technologies on the market. However, GATF has three publications, Computer-to-Plate Automating the Printing Industry, The Essentials of Computer-To-Plate Technology, and Computer-To-Plate Primer, which have chapters discussing the plate technologies. Also, a book published by International Paper called Pocket Pal has a chapter on the subject. All of these publications can be ordered through GATF. 6. I am not aware of any one lab that has all of the plate technologies available. GATF has most of them that we use for teaching, research and GATF's own printed materials. We don't have the room for all of them, but we have most of the them. For example, there are three types of thermal plates and we have the most common one. RIT also has a representative sampling of technologies, but I am not aware that they have them all. Gary Jones Graphic Arts Technical Foundation 200 Deer Run Road Sewickley, PA 15143 412/741-6860 x608 - Phone 412/741-2311 - Fax



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