# Halftone dots in center of screen closing up after drying...



## earwicker7 (Oct 27, 2014)

I've been having issues with a design which has some halftones printed at 45 lpi on a 230 mesh. I've burnt multiple screens, and no matter what, the same issue keeps occuring... a good portion of the 9% halftones won't print onto the shirt, but only in the center.

I've tried tweaking everything... I've raised the drop density on my rip software, made sure I only used perfectly coated screens, made sure the exposure times were fairly tight (on the exposure calculator, I'm always between 6 and 8, with 7 being the perfect target), etc. At this point, I'm pretty positive that I have the exposure process down pat.

I burned a screen yesterday, and after washing it out, and patting it dry with some newspaper, I put it over a light desk... everything looked fine; the 9% halftones seemed to have washed out. I went and put it in the rack to dry... I put a fan by it, and the room has a dehumidifier in it.

I went to check it today, and it looks like some of the 9% halftones have closed up in the same place they always do... in the center of the screen. The rest of the 9% came out fine. 

I'm trying to use some logic here to figure out what is happening... I am guessing that gravity would cause any moisture which is still in the screen to pool toward the center. Assuming I'm right, it seems that it could be multiple things: that I'm not drying things up well enough, that the moisture is causing the emulsion to swell, something in the water I use for washout is causing it (don't know why, as I have a water softener), or maybe I'm not washing out long enough, and there is still emulsion on the screen, and it is clogging the 9% dots.

Anyone have some ideas on how to troubleshoot this? I'm spending WAY too much time on this, and a lot of people are wanting to order shirts with this design on it (I make my own shirts for my clothing company, and I foolishly leaked this design before I started printing them).

Thanks!


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## earwicker7 (Oct 27, 2014)

I've attached a picture of the situation... it's with a cell phone, so not the best quality. The screen is on my light desk; the banding isn't on the screen itself... it's an artifact like when you take pictures of a television.

Anyways, if you look at all of the circled areas, they're all 9% halftones. The blue circles are ones in which the light clearly shows through the dots, and those will print. The red circle shows an area where you can see the halftones, but they're not completely open, and no ink goes through.


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## Rocky Top (Feb 13, 2012)

Try blowing it dry with an air compressor or canned air. (?)


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## jgabby (Mar 29, 2007)

Seems the center have more exposure maybe because of your light setting. 

If you decrease exposure time, can you get these 9% halftones in the center ?

What kind of light do you have ?


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## earwicker7 (Oct 27, 2014)

Rocky Top said:


> Try blowing it dry with an air compressor or canned air. (?)


I have considered getting an air compressor. My understanding is that you have to watch out for ones which may have water or oil in the lines... I don't know anything about air compressors, so I'm not sure exactly what makes and models to look for.


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## earwicker7 (Oct 27, 2014)

jgabby said:


> Seems the center have more exposure maybe because of your light setting.
> 
> If you decrease exposure time, can you get these 9% halftones in the center ?
> 
> What kind of light do you have ?


It's a 240 watt UV unit with a compression lid.

I haven't yet tried underexposing... I know it's an option, but I want to use it as a last resort. Maybe I'll try it over the weekend and see if it works.


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