Author Topic: High detail screen making issues  (Read 8247 times)

Offline Sbrem

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Re: High detail screen making issues
« Reply #30 on: November 01, 2018, 08:46:21 AM »
Well stated, Andy...

Steve
I made a mistake once; I thought I was wrong about something; I wasn't


Offline StinkyDaddy

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Re: High detail screen making issues
« Reply #31 on: November 01, 2018, 10:14:41 AM »
When I started out in '92 I made my own exposure unit, 2 - 48" shop light fixtures with black light bulbs from Spencer's Gifts. I used a big piece of 1/4" glass over the lights and weighted the screen and art with 2 more pieces of 1/4" glass taped together and stuffed inside a t shirt to keep from cutting the screen (or me). I put a barbell weight on top of the glass pieces to give it some extra. I used this until I made enough money to buy a expo unit. It worked well for line art, but could not reproduce halftones with any consistency.

Offline easyrider1340

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Re: High detail screen making issues
« Reply #32 on: November 01, 2018, 10:25:21 AM »
I just asked a question to someone else about vacuum vs weights on exposure unit. 

What does the data say?  Does data exist?   What is the pressure difference between vacuum exposure unit vs weight/foam unit?

Thanks
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Not even close!

From this article https://www.mrprint.com/blog/841-exposure-systems-finding-the-right-cure

A vacuum system with fifteen inches of mercury develops 3,775 lbs of pressure, holding the screen and film evenly together on a 23” x 31” screen! That kind of pressure is hard to match with plywood and weights!
Well there you go!   Thanks!
Why doesn’t it break the glass?  In theory, if I stacked 3775 lbs on my plywood and foam, I’d get same result as vacuum top (at 15” mercury)?   Not that I plan on stacking my wife’s Lexus on top of my exposure unit...  lol


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Offline Frog

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Re: High detail screen making issues
« Reply #33 on: November 01, 2018, 10:32:09 AM »
I just asked a question to someone else about vacuum vs weights on exposure unit. 

What does the data say?  Does data exist?   What is the pressure difference between vacuum exposure unit vs weight/foam unit?

Thanks
Sent from my iPhone using Tapatalk

Not even close!

From this article https://www.mrprint.com/blog/841-exposure-systems-finding-the-right-cure

A vacuum system with fifteen inches of mercury develops 3,775 lbs of pressure, holding the screen and film evenly together on a 23” x 31” screen! That kind of pressure is hard to match with plywood and weights!
Well there you go!   Thanks!
Why doesn’t it break the glass?  In theory, if I stacked 3775 lbs on my plywood and foam, I’d get same result as vacuum top (at 15” mercury)?   Not that I plan on stacking my wife’s Lexus on top of my exposure unit...  lol


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We'd probably also have to calculate just how thick the plywood would have to be to not flex at all and evenly hold her Lexus without putting more pressure under the tires and possibly breaking the glass there.
That rug really tied the room together, did it not?

Offline Chadwick

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Re: High detail screen making issues
« Reply #34 on: November 01, 2018, 02:33:42 PM »
Lexus on an exposure unit, that'd make a good pic.
 :)
Anyhow,
I'm not sure how much you know Fleetee, so please don't take offence.

If I recall, my explanations to the trainees went something like this..

Very, very, generally speaking regarding mesh counts.
For exposing linework, you could use 80 mesh if you felt so inclined, without losing too much detail.
Once you get into halftones, finer mesh is required.
For example, I used artwork ripped at 40lpi, exposed on 150-160 mesh everyday for years.
( that was just our 'always works' set it and forget it )
If I ripped the artwork at say, 55lpi I couldn't hold certain ranges, so a finer mesh was required.

To keep it simple, think of mesh in ink thickness terms, and halftone exposure ability.

But, as almost everyone has mentioned, you NEED a vacuum blanket, or you will chase your tail
with workarounds and frustration all day long ( I know, I have ), unless you're doing the real simple stuff.
And of course, all those important variables with bulbs, emulsion, coating, etc, ad nauseum.

Many folks on here with tons of knowledge on the science of it all.

Hope that helps.
Cheers.


Offline tbarnes

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Re: High detail screen making issues
« Reply #35 on: November 05, 2018, 03:47:29 PM »
hey guys, are the higher mesh counts limited to high detail designs? for example can a 280 do a design that is meant for 110 or 160 design? another way to ask the question would be can a design that can be successfully done on a 110 or 160 also successfully be done on 280 or even a 305? the reason why I am asking is because I am ordering a big bulk of screens, and now knowing that the lower mesh count can not only do half tones but also cant do detailed designs like i attached on the op, i much rather spend a couple extra dollars on the higher mesh counts if that means that the mesh counts can be more versatile and buy 200/230/280 mesh screens so that they can do both the very detailed designs AND the simple designs.

225/230 will work on almost anything. It is definitely the most versatile mesh count. You can use it for solid vector art and get a nice soft hand feel and it will have no problems printing fine lines or half tones down to 3%. Works well with plastisol and waterbase. If you are buying in bulk that is the way to go. I would definitely invest in a vaccum lid if you are concerned about printing high detail though.

-Ty