Author Topic: exposure time  (Read 3095 times)

Offline ZooCity

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Re: exposure time
« Reply #15 on: June 22, 2015, 08:51:06 PM »
If you need/want speed, stick with 5k MH.  If the Starlight could shoot 2up it would be more of a contender to replace MH in the speed category but still slower.  Or you could buy two or more Starlights.... 

In any case this discussion of speed isn't a knock on the Starlight, my understanding is it was not designed for speed.  The main benefit we see is lower power consumption and small footprint.

You can actually get a 7s expo time with HVP, with glass and film, with a good 5kw positioned to shoot 1up.

But even with DTS those super fast times with the Starlight are either extremely fast shooting emulsions or people just aren't fully exposing, which is fine for some all plastisol shops, no go for the rest of us.  When some manufacturer matches an emulsion to the Starlight's LED spectral output the times have the potential to get quite fast. 

M&R will test your emulsion for you.  Give them a call.   They emulated one of our screens- same mesh, emulsion, amount of diazo, right down to the same scoop coater I believe so we could double check the times against each other. 


Offline ZooCity

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Re: exposure time
« Reply #16 on: June 22, 2015, 08:53:22 PM »
Zane: I agree on all your points ;)

Exposing a screen as fast as the DTS can spit them out is fast enough for me.

That's a great point.  If the expo unit keeps up with your positive output, that's all that should be needed regarding speed.

Offline Ross_S

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Re: exposure time
« Reply #17 on: June 23, 2015, 10:10:37 AM »
I have a starlight and don't change any of my times for discharge screens.  I also have a similar emulsion (CCI).  I do post expose my discharge screens though.

Offline cleveprint

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Re: exposure time
« Reply #18 on: June 23, 2015, 10:29:39 AM »
sorry for not getting back right away, we lost phone and internet last night and its just getting back on today. thanks for the starting info. as i said, i will test for sure, but its always nice to have a starting point. as far as the 7/8 seconds for regular plastisol, we do not seem to run into any issues there. they might not be fully exposed, but very rarely do we get breakdowns.

im going to give it a go in the 14-15 second range and go from there. i might as well post expose too, probably cant hurt.

Offline ABuffington

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Re: exposure time
« Reply #19 on: June 23, 2015, 11:30:05 AM »
To reinforce the thread here.  Yes 1:1 coat thick edge or 1:2 thin edge is all you need to get good EOM with Aquasol HVP.  With fast exposing systems like the Starlight there is such a thing as too fast.  Image vs Exposure, both can make a print, one will outlast the other on press.  Bake the Cake!  No baker has ever said, lets try baking bread in half the time today, the inside would be a gooey disaster, same with emulsion where cross linking is incomplete it will soften and break down.  It's what you can't see that matters.  With waterbase you want the squeegee side well exposed.  Fast exposures can prevent the squeegee side from proper exposure where mechanical abrasion with discharge and wb can wear away the emulsion quickly.  As mentioned, the goal is to find a balance between complete exposure and getting details out.  The MH vs Starlight has been discussed a lot here.  Both work, just have to fine tune the times and the coating technique.  Resolution, durability and all play a part.

Alan
Alan Buffington
Murakami Screen USA  - Technical Support and Sales
www.murakamiscreen.com