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  • How to develop better diazo film?
    Date :2013-7-10


    1.Developer must be level to ensure proper ammonia flow. Locate the developer in an area where temperatures don't exceed 78 F. This helps prevent a vapor lock condition at the ammonia metering pump.


    2.Position the developer to simplify maintenance. Every month, wipe down the main drive belt or rollers, clean the Teflon mesh screen, vacuum any dirt and debris, lubricate parts, and advance the tubing on the metering pump.


    3.Proper venting is essential. An auxiliary exhaust system that vents to the outside may be needed to supplement the developer's internal blower. But don't over-vent: this can deplete the levels of ammonia and heat that are essential to developing the phototool f ilm. A 500 cfm auxiliary blower with an attached adjustable damper is a popular remedy. Or try this: Use 2" PVC pipe running from the developer along a wall up to the building roof. Place the adjustable damper in line on the PVC pipe within easy reach of developer, then place the blower just below the roof line. Adding a weather cap on the roof outside willhelp prevent a backflow condition.


    4.Keep the metering pump tubing free of kinks, pin holes and outside pressure. These conditions can restrict flow of ammonia to the developer. The result is often an underdeveloped phototool and possible overheating which can dimensionally change the f ilm.


    5.Typically, developers come with a drain system for evacuating condensation. Make sure the tubing is free from any obstructions or kinks that could restrict drainage. Regularly check the drainage bottle and empty as required. Never put the drain bottle solution back into the developer as it is mostly water.


    6.If the developer is belt driven, be sure belt tension is properly adjusted. If there is too much tension, heat and ammonia will escape the development chamber and the dimensional stability of the f ilm could be altered. Too little tension andthe f ilm will not be driven into the unit or will stall. Many diazo developers have a "floating" belt design - the adjustment should be so that the belt is very loose and "drags" over the development chamber. The adjustment should be made to have the belt very loose and tracking evenly over the developing chamber.


    There is no such thing as a one-pass developer! Sure, many developers can achieve ful l development if all conditions are perfect, but they rarely are. Seldom is only one piece of f ilm processed. As a rule, process each piece of standard diazo film three times through the developer; four times when using chemical resistant diazo f ilms. Each time you pass the film through the developer, it draws both ammonia and heat from the developer. Also, most jobs have more that one sheet of f ilm. A developer must have time to replenish itself.
    Remember these simple A-B-Cs of diazodevelopment:
    A. Maintain a temperature range of 150 to 160 F at the film plane.
    B. Use ammonium hydroxide with a strength of 26 to 30 baume.
    C. Maintain a moist (vaporized) developer chamber environment.


    7.Maintain the correct temperature range to ensure proper development and prevent dimensional change. Use a 140 to 180 temperature tape to verify the "f ilm plane" temperature. Place the temp tape on the sensitized side of thefilm and pass it through the developer. Look for a reading between 150 and 160 F.


    8.If a developer is too cold, the film will not fully develop. If too hot, expect dimensional change to the finished phototool. Also, never assist the film to leave the developer. Even the slightest tug can dimensionally alter the f ilm. Turning a developer on and off during the day can compromise f ilm development and performance. Always (!) give the developer 30 min. to warm up. When the developer is f irst turned on, the heat will spike up. As the ammonia is heated and vaporized, it cools down the developer. After 30 min. or so, the system should balance and remain constant. Many developers in the field have a thermometer located on the side of the unit. This only reads the developer tank temperature, not the "film plane" temp (what the film actually sees). We are only concerned about the f ilm plane temperature. The only way to know the film plane temp is by using a temperature tape. These are readily available from the f ilm manufacturer and/or distributors.


    9.The term "moistness" refers to the use of liquid ammonia delivered via a metering pump to the developer. The pump should deliver 15-17 cc/ml per every 10 minutes and thus provides a "moist" developing environment.Many shops use technical grade (also called diazo grade)ammonia. Because it's cut with tap water, minerals from tap water will build up deposits on the evaporator tray. That inhibits free flow of the ammonium hydroxide. Specify semiconductor approved, analytical reagent (pure ammonia) or U.S. pharmaceutical grade ammonium hydroxide, 28 to 30 baume. This costs a little more, but helps improve the eff iciency of the developer. Never use ammonia that is less than 26 baume. Less than 26 Baume A ammonia under numerous conditions would result in an "under developed" f ilm. It is always best using 28-30 Baume Ammonia to help prevent under developing of the diazo emulsion. Use a hydrometer to test baume levels and change out the ammonia as needed.


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