"He who marches out of step hears another drum." ~ Ken Kesey
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?
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.
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
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. pierre
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. :-)Quote from: 3Deep on September 18, 2019, 01:29:02 PMAs 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.Terryhttp://www.AllegiantGraphics.comhttps://www.Facebook.com/AllegiantGraphicshttps://www.Instagram.com/AllegiantGraphicsSent from my iPhone using Tapatalk
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.
Thank you for the advice and questions. Vacuum is not tight enough. Hopefully I’ve resolved that and will retest tonight. I “believe” my film is dark enough. In large areas, you can’t really see light through it. Epson 1400, All Black, Accurip. Should I bump up LPI 5-10 to get a better representation of 45?ThanksTerryQuote from: blue moon on September 18, 2019, 07:36:04 PMugh, 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
you need a thick enough stencil and a 1/1 might not be it. Slow coat with dull side might be OK.Wow I can't believe I'm gong to disagree with you there Pierre, but all my testing is in my shop, so it makes a difference. I coated thicker screens and my LED just didn't do the trick, so 1/1 was perfect, plus I'm thinking I coat the print side first then the squeegee side which I feel push most of the emulsion back to the print side which gives me a thicker print side anyway, I'm wrong in thinking this?, I've coated s mesh with the round edge of the coater and to me it was just to much emulsion on the screen so I even coat them 1/1 now, seems like the s mesh just wholes more emulsion for some reason.darryl
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!pierre
Tons of good advice in this thread! Emulsion thickness will definitely play a big role here. We coat 1:1 sharp with PHU so I would try that thinner coating as an experiment if you can’t measure the EOM. Pressure washer is pretty critical in my opinion. If it’s too soft for the washer then you have other problems in exposure. I suggest a good pre-soak of the screens before rinsing though. I swear our halftone resolution is better now that we are using a post-exposure dip tank. I did want to touch on this note from Pierre though.Quote from: blue moon on September 18, 2019, 07:36:04 PMFilm 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!pierreSomeone gave me some great info and advice about this one time. Opacity doesn’t have much to do with UV blocking. Think about sunglasses...And putting down too much ink is going to make it difficult for those halftones to not be gaining. AccuRip does have a wonky default dot curve but it can be exaggerated by other factors like the film and exposure.My advice for that is to do the density test, and expose it! You’ll see right away which blocks wash out fine. My experience was that we were at a 12 on the density scale because it was opaque. Tested it and got cleaner detail with less ink and same exposure at a level 4. Dark film is definitely key here but too heavy is gonna give halftone problems too. Sent from my iPhone using Tapatalk
Author
Topic: Looking for advice on halftones (Read 6978 times)
