Author Topic: Post Expose An Emulsion  (Read 1503 times)

Offline willy35

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Post Expose An Emulsion
« on: March 19, 2015, 07:41:33 PM »
Hi,

Since I see there is great emulsion specialist on this forum, I would like to know once and for all when to post expose an emulsion.

Since there is photopolymer and diazo emulsion can both be post exposed ?

Is there any advantages whatever your light source is ?

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Online Frog

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Re: Post Expose An Emulsion
« Reply #1 on: March 19, 2015, 08:20:19 PM »
Only  photopolymers will see any effect. (I  learned only recently that the diazo in dual cures does not take this characteristic away, and they benefit as well.)
Best light source? the sun.
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Offline Orion

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Re: Post Expose An Emulsion
« Reply #2 on: March 20, 2015, 10:22:45 AM »
Pages 6-7....click here
Dale Hoyal

Offline willy35

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Re: Post Expose An Emulsion
« Reply #3 on: March 20, 2015, 01:05:42 PM »
Thank you

the link is good, I love this kind of informations.



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San Gen Shugi - real place (Gen-ba), real part (Gen-butsu), reality (Gen-jitsu)

Offline ABuffington

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Re: Post Expose An Emulsion
« Reply #4 on: March 20, 2015, 01:57:47 PM »
Post exposure for Pure Photopolymers helps strengthen the stencil and complete the exposure process.  However it should not be substituted for a good initial exposure. It is better to expose the emulsion in the initial exposure for the maximum possible amount of time possible while still achieving good details and resolution. Our emulsion often has wide lattitude of exposure which allows for complete exposure.  Under exposing emulsion to achieve all details possible and then relying on post exposure to complete the exposure will never achieve the screen strength that a complete initial exposure followed by post exposure in the sun can achieve.  Dual Cures see some added benefit of post exposures along with the heat and drying to get a completely dry stencil.  For Diazo the post exposure in the sun is a good drying technique.  Pre-stretched Screen users of fine mesh should know that the heat of the sun can cause aluminum frames to expand and increase tension to levels that could pop the mesh.  Monitor frames for heat.  When I put my light meter in the sun it went past 23,000 watts and was still climbing. When the screen is wet, 20 minutes is enough time in So Cal to dry and post expose.  Drying the screen well for discharge and wb along with post is just as important as post exposure.  Rushing a freshly made screen to press for discharge will result in breakdown since the emulsion may still have moisture on the inside of the coating.
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com