Looking for advice on halftones

[easyrider1340]

I lurk here MUCH more than I post.  I appreciate being allowed to soak up the knowledge from all of you, I’m certainly not in your league!

My question(s) is about stencil making with halftones. 

Let’s say, exposure times are dialed in to a 7 on Stouffer scale, screens coated manually, films are dark, using Accurip, 305 mesh, 45 LPI. 
Are you able to produce a stencil that looks exactly like your film?  Meaning every dot is developed?  What is good enough?   

I’ve read that it takes high end equipment to get dots below 7-10%.  Is that acceptable?   I’m a manual, garage, part time shop - just trying to learn and get better. 

Thanks so much
Terry

[Sbrem]

Light source? I've only ever used point source lights, from Carbon Arc, to Metal Halide, and now Saati's Pro-lite 450. Point sources will make better halftones, but I believe plenty of folks using fluorescent tubes get it figured out, maybe some will chime in. At 45 lpi, on 305, you should be able to get most every dot. As for getting the dots on the screen the exact same size as the film, you should be very close, but even so, when you print, they will gain size, which of course teaches us how to compensate.

Steve

[easyrider1340]

Thank you for the response.  I currently use a 50 watt LED that is a DIY.   (I have an E200 on order).  I also have a fluorescent tube exp unit that I started with. 
I will post last nights exposure example in a moment.

Light source? I've only ever used point source lights, from Carbon Arc, to Metal Halide, and now Saati's Pro-lite 450. Point sources will make better halftones, but I believe plenty of folks using fluorescent tubes get it figured out, maybe some will chime in. At 45 lpi, on 305, you should be able to get most every dot. As for getting the dots on the screen the exact same size as the film, you should be very close, but even so, when you print, they will gain size, which of course teaches us how to compensate.

Steve

[easyrider1340]

This is 305, PHU2, 6 on scale so underexposed.  But the other thing I noticed is emulsion was falling out of the image area during pre-rinse.  This is first time I’ve ever used PHU2 (typically used dual cure in past).  ...and I used pressure washer to rinse.   

So I believe I have 2 obvious issues
- continue dialing in exposure to a 7
- stop using pressure washer

Am I missing anything fundamental?

I really appreciate the feedback.  I’ve been printing part time for years, but spot color prints are much more forgiving. 

Terry





Sent from my iPhone using Tapatalk

[3Deep]

As Steve said emulsion is key for different light source, also when I had my tube unit I used a dual cure emulsion and color mesh, which seem to burn a hold lot better with my halftone work.   I just started using a LED point light which is a 100 watt light and I'm getting better dots at 35 seconds using HXT emulsion, but what I've seen VPR might be a real good emulsion for LED exposure, I heard someone say it's not how long you expose, it's how well you expose the screen.

[Frog]

I really appreciate the feedback.  I’ve been printing part time for years, but spot color prints are much more forgiving. 

Terry

I don't want to nit-pick, nor let the discussion go too far astray, but the more statements like this go un-corrected, the more the terms will be misunderstood.
Spot colors can be halftoned, or solid.
Spot colors are simply colors printed with a single ink, either stock or mixed, rather than colors mixed in and by the printing process. 4 color process, simulated process, index prints, etc.

[easyrider1340]

I really appreciate the feedback.  I’ve been printing part time for years, but spot color prints are much more forgiving. 

Terry

I don't want to nit-pick, nor let the discussion go too far astray, but the more statements like this go un-corrected, the more the terms will be misunderstood.
Spot colors can be halftoned, or solid.
Spot colors are simply colors printed with a single ink, either stock or mixed, rather than colors mixed in and by the printing process. 4 color process, simulated process, index prints, etc.

You are correct.  And this job is spot colors with halftones.  I should have said block-letter, solid block or similar.   Thank you. 


Terry

Sent from my iPhone using Tapatalk

[easyrider1340]

I may have a coating issue.   I coated 2/1.   Maybe emulsion was too thick thus losing the detail. 

I don’t have a method (that I know of) to measure EOM, but maybe I should try a 1/1 to see if that grabs the detail. 

I really think underexposed and the pressure washer compounded my issue. 

But my original question was answered, and I should target my process improvement toward holding every detail.   I just wasn’t sure if there was a “good enough”.   I’m sure there are thousands of garage printers who do less research than I on this topic, thus “good enough” is standard.  But I’d like to separate myself so that I have the edge.  If that makes sense. 

I appreciate the advice, and I’ll keep lurking.  :-)

As Steve said emulsion is key for different light source, also when I had my tube unit I used a dual cure emulsion and color mesh, which seem to burn a hold lot better with my halftone work.   I just started using a LED point light which is a 100 watt light and I'm getting better dots at 35 seconds using HXT emulsion, but what I've seen VPR might be a real good emulsion for LED exposure, I heard someone say it's not how long you expose, it's how well you expose the screen.

Terry
http://www.AllegiantGraphics.com
https://www.Facebook.com/AllegiantGraphics
https://www.Instagram.com/AllegiantGraphics
Sent from my iPhone using Tapatalk

[Frog]

I really appreciate the feedback.  I’ve been printing part time for years, but spot color prints are much more forgiving. 

Terry

I don't want to nit-pick, nor let the discussion go too far astray, but the more statements like this go un-corrected, the more the terms will be misunderstood.
Spot colors can be halftoned, or solid.
Spot colors are simply colors printed with a single ink, either stock or mixed, rather than colors mixed in and by the printing process. 4 color process, simulated process, index prints, etc.

You are correct.  And this job is spot colors with halftones.  I should have said block-letter, solid block or similar.   Thank you. 


Terry

Sent from my iPhone using Tapatalk

Ah, well it was the section you initially chose in which to post, that helped confuse me. I'm moving it to Screen Making

[Maxie]

You get halftone detail you want to underexpose, 7 on the Stoufer is too high.
You also need to check EOM, it will be hard to hold detail on a thick emulsion.
How good is your vacuum?

[easyrider1340]

Thank you.  I have no way to check EOM.
Vacuum is DIY.  Not sure it’s good enough. 

I’m awaiting delivery of a Vastex E200.  Hoping that will help. 

You get halftone detail you want to underexpose, 7 on the Stoufer is too high.
You also need to check EOM, it will be hard to hold detail on a thick emulsion.
How good is your vacuum?

Sent from my iPhone using Tapatalk

[3Deep]

From what I see your vac is not pulled down tight enough, if that is a full vac pull down?, I've been told and I think someone mention it here that LED is not really a good light source for thick coated screens...1/1 should be fine, or just increase your burn time.

[im_mcguire]

From what I see your vac is not pulled down tight enough, if that is a full vac pull down?, I've been told and I think someone mention it here that LED is not really a good light source for thick coated screens...1/1 should be fine, or just increase your burn time.

This!
When we switched to a LED, we have ran nothing but 1/1 coated screens.
We have yet to have an issue with breakdown and get great dot results (when we have those jobs) in the 5% range.

We use Murakami HVP emulsion with a 7.5 second burn.
I will also agree that the draw down on your blanket could use some attention.  That should suck down tight to give good positive contact between the glass and your film.

[Frog]

a note on vacuum.  Really good contact between film emulsion and screen emulsion is probably even more valuable than a point light source in holding small detail. That's why so many folks got (get) great results with fluorescent tubes. Even if the light is coming from multiple directions, good contact helps it from undercutting.

[blue moon]

ugh, not sure where to start. . .
you need a thick enough stencil and a 1/1 might not be it. Slow coat with dull side might be OK.
Vacuum needs to be so tight that the film has an oil sheen looking pattern on it. If you don't see it, it's not tight enough. As Darryl said, what you are showing in the picture is not enough!
Film needs to be dark! What are you using to print it? If you look at the lights in the shop through a dark part of the film you should barely be able to see them.
PHU2 manufacturer specifies 7 on the scale. Stick with it. If your film is dark, overexposing is not an issue. Underexposing is ALWAYS an issue!
You should be able to dial in and hold about 5-6% with the specs you mentioned. AccuRIP prints dots larger than advertised, so your 45 lpi is probably closer to 35. A 5% at 35 is a really big dot and you should work on your screens until you can hold it.
The Vastex unit we tested was good to about 5-6% at 55 lpi (calibrated). Due to numerous LEDs it will not be as good as a single point light source. See if they have a MH that is a single point. This is not to say that their unit is bad, just the opposite, it was the best on the market when we did the testing, it would just mean that you are starting with a handicap. If you are OK with doing really good work rather than great work you'll be OK!

pierre