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A guide to exposure determination and the impact of artworkWilliam ShorterCPS Technical Sales Executive/Product Manager
Factors to consider with exposure systems
• The quality of the UV light.– Wave length:
• Diazo• Photopolymer
– Avoid Infra Red• The power of the
light.– Distance
Factors to consider with exposure systems
• Distance from the stencil.– 1m = 30 seconds.– 2m = 900 seconds.
• Angle of the light.– Diagonal of the
screen.Increase in exposure time
Factors to consider with exposure systems
• Vacuum– Good seal– Don’t use white card at
the back
• Integrator or time?
Factors to consider with your artwork
• Quite simply, you can produce bad prints from good artwork, but you cannot produce good prints from bad artwork.
Factors to consider with your artwork
• Opaqueness of ink jet media.
• Must absorb UV light in the region of 350-420 nanometers.
• Don’t overload ink jet positives with ink.
• The smallest dot or line you can print is controlled by the mesh thread width.
Factors that affect durability
• Optimum Exposure– An Exposure
Calculator or step wedge is an important calibration tool.
– Full exposure is when all the diazo has cross linked.
• Indicated by colour change.
– Brown to purple– Green to blue
Factors that affect durability on the press
25%Optimum Exposure
50% Optimum Exposure
75% Optimum Exposure
100% Optimum Exposure
• Masks and positives with poor masking ability will result in you needing to under expose the stencil film or emulsion, compromising the durability and finished print quality.
CPS LtdChemicals Products and Serviceswww.cps.eucps@cps.euT: 01235 773240F: 01235 771196
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