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| Posted on 10/3/07 at 10:57 AM | |
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All photo sensitive materials are best stored in a cool 'dry' place. They're in buckets, or sealed containers, so dry is not so important 68°F is lovely. More important for drying screens is a DRY room less than 50% relative humidity. Everybody should have a Home Depot hygrometer ($9) or Radio Shack Digital ThermoMeter/Hygrometer ($19)to measure air quality. Un-sensitized emulsion is very stable, it's the diazo sensitizer that ages like milk or lettuce. After a year, it just doesn't work as well as when it is fresh. This is taken into condsideration when companies publish shelf life. Diazo is good after a year, Ulano just doesn't warranty the product. You can always purchase fresh diazo. Water is the diazo killer, not air. If emulsion is exposed to air, it skins. You scrape the skinned emulsion off and throw it away. Once the sensitizer is added to the emulsion it water starts to break the chemical down and after 30 days it exposes differently than fresh emulsion. Once you have coated and dried the screen, there is no water to attack the sensitizer and your screen is quite stable in a dark room (best), or using yellow safe lights. The best practice is to turn the lights off when nobody is in the drying/coating room/closet. Emulsion will not cross link by itself. It needs outside stimulation of UV-A energy or heat above 110°F for several days. ____________________ Richard Greaves, ASPT Ulano Corp. New York Technical Services 718-943-1338 direct | |
  
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