# Half tones washing out?



## Albie1 (Sep 2, 2009)

Hello I'm having a problem with my halftones washing out. I'm using a new gallon of ryonet hifi emulsion. I'm using a 305 mesh screen coated 1-1 . Film is printed with my r1800 using fastink and fixxons waterproof through filmmaker rip. I made the film with 42 line halftones at 25 deg. My exposure unit is a 6 bulb uv 25x36. Last week with a step wedge I found 2 min with a 305 was the best. So I coated the screen 2 days ago turned on the dehumidifier and let it dry for 2 days . Now this is in my attic which one room is the dark room but it gets about 42- 55 degrees up there since it's winter and I don't run heat up there. I put the film on the screen and burned it for 2 min then put it in the washout sink I sprayed it with cold water lightly on both sides then let it sit about a minute (all this is in the darkroom the screens never leave the room). After a minute I spray it again withthe water and still nothing washes out .. Then I keep spraying it with water and I start to get some washout but not alot .. Finally after 3 min Im frustrated cause the halftones aren't washing out so then I turn the nozzle on the hose to more of a stream and then I loose the halftones cause it blows them out... I can rub my finger on them and the come right off... What is it I'm doing wrong? Is it the temp in the room messing with the emulsion ? Im getting a new exposure unit in a few weeks msp3140 but for now this is all I got to work with! Any ideas guys


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## malibusurfer (Dec 21, 2006)

I'm guessing your under exposing based on the info you've given. Just for giggles try 2x the amount of exposure time. Emulsions these days have a lot of latitude and should be forgiving regarding exact exposure times. Your drying time after you coat your screen should not take 2 days. If you have a heater, a fan and a semi dark room, 1 hour should be sufficient. I expose 100+ screens per day via metal halide exposure units for as little as 35-45 seconds for some images; although florescent bulbs have a much lower UV light curve your timing needs to be adjusted up. Sounds like your particular set up just needs some experimenting/fine tuning - good luck. Mike-


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## Albie1 (Sep 2, 2009)

Mike it's not taking 2 days to dry it was in the room on the drying rack for 2 days. I'll try exposing it for 2 times the time now but I'm getting block letters on a 110 to washout fine in 3 min so I'm alittle afraid to go to 4 min on a 305 . But at this stage I'll try it. Albie


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## BroJames (Jul 8, 2008)

The best exposure time on a step wedge is almost guaranteed to be an under exposure. Depending on exposure time intervals, I would suggest you use the next or 2nd next higher time in the wedge. 

A jet, full or any tight stream is almost guaranteed to wash out half tones. What you want some kind of cone pattern that delivers a fine spray over a wider area. Your mains pressure should also be high enough.

It is also possible your black ink isn't black enough. It may not be that evident with spot images(or block letters) but shows in half tones. 

But chances are, you just need to find the correct combination of the correct exposure time and using the correct(fine) spray pattern with enough pressure behind it. May still be underexposure but you'll get your halftone.


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## PositiveDave (Dec 1, 2008)

I don't think that it's the positive, the halftones are the holes in the positive.
I think that the screen might need degreasing/abrading?


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## BroJames (Jul 8, 2008)

That's just an idea based on this


Albie1 said:


> ...After a minute I spray it again withthe water and still nothing washes out .. Then I keep spraying it with water and I start to get some washout but not alot .. Finally after 3 min Im frustrated cause the halftones aren't washing out so then I turn the nozzle on the hose to more of a stream and then I loose the halftones cause it blows them out... ...


but so far, my encounter with poor degreasing is whole chunks of emulsion washing out even with low water pressure.


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## GrapeCloth (May 20, 2010)

Yeah degreasing is ridiculously important. You can find degreaser/reclaimers online at most screen print product websites. Lifesaver!


Live The Good Life.
www.GrapeCloth.com


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## amili-amili (May 3, 2010)

Im having the same issue... I have a 305mesh coated 1/1 using ryonet svp (blue) emulsion; fiim printed with a 4880 epson all black system; 65-70lpi and 22.5-45 frqz (ive tried several variations); burned using 1000w MH 55sec-2min ( around 2min the screen is harder to wash out) ...oh and my artwork was created using photoshop bitmap method 600dpi


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## BroJames (Jul 8, 2008)

try printing at 1200dpi.

also try 55 lpi and see what happens. If it works then the problem is more likely to be exposure and/or emulation. Possibly emulsion washout method.


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## InkedApparel (Mar 18, 2009)

I have learned that halftones need about half the burntime than block letters need....try cutting your burn time down by 1/2 

Hope this helps

Inked


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## Zenergy (Apr 14, 2011)

Upping the exposure time is the way to go on this. I'm using HiFi an I normally expose spot colors at 2:30, but I had some halftones that kept blowing out. I ended up going all the way up to 8:30 and they washed out beautifully. I'm exposing on 2 500w shop lights at 16".


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## beanie357 (Mar 27, 2011)

Temperature does have an impact on the process. It sounds like under exposure. Designs with halftones burn same Lu as anything else at our plant.


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## DigitalMayhem (Aug 4, 2007)

Amen beanie. Just because your block letters still wash out when you underexpose them does not mean they are still not underexposed. 

Sent from my LTEvo.


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## iamavol (Aug 8, 2006)

I was having the same issue with half tones on 230. I cut my exposure to 90 seconds, a finer rinse and post hardened by putting them back on the exposure unit. Perfect results with the same equipment you are using


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