# Parts of Emulsion are gummy and wash out/bubble



## AbbieRoad (Feb 24, 2007)

I'm relatively new to screen printing. I've been doing it for a year but at a slow speed as I have a lot of other hobbies and a toddler as well. 

I'm doing some shirts for my hubby's firehouse, and this is the third or fourth time this has happened to me - 95% of the screen will wash out completely perfect, and then one letter, or, 5% of the design will be gummy, bubble, wash out or move around. I could easily peel off the emulsion from this spot. 

I took a pic - here: 








more in my flickr too, if you want to see more pics: http://www.flickr.com/photos/abbieroad/

Some of the letters/design has this weird "algae" type look to it around the edges, like a feathering near the worst part that's pictured. 

I'm assuming that the certain part was too thick and didn't cure long enough. If i cure it longer - like for 7 minues, will that make the rest impossible to wash out? The rest washes out perfectly right now. 


Here's what I'm doing: 
I'm using Ulano QX-1 Emulsion, on 140 mesh screens. I am coating with a scoop coater, but it's not big enough for the whole screen so I have to do 2 passes. This particular screen I dried for over a week, I coated it last Monday and it dried in a cool dark box in an air conditioned house for a week. 
When I burn the screen, I use doubled up transparencies for extra darkness, and I burn them for about 5.5 minutes on an exposure unit - no vacuum, just a basic one I bought from Ryonet. 


Thanks in advance
Abbie


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## MBrhythm (Mar 1, 2007)

Try to expose a little longer. Maybe do a "Step-Test" to get the right exposure time. 
After you wash out the design, set the screen in the sun to dry and fully expose it again.

Also when drying your screens in the box in your house, make sure there is no humidity. 

Good luck. I hope this helps


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## moe_szys1ak (Jun 16, 2008)

If you can peel the emulsion off or it is bubbling, then you may not have degreased the screen properly, or washed all the degreaser out. Also, you should make sure the screen is completely dry before applying the emulsion. Combine this with a longer exposure and I think you will experience better results.


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## totalstitch (Apr 8, 2007)

Abbie,

I just switched to the QX emulsion (pink) and had a similar problem. I tried everything from degreasing more then normal, letting them dry longer, longer exposure and so on. The last thing I did is add a dehumidifier (East Coat Humidity) and it helped out alot. I was using the Diazo and notice the QX will wash out easier, so now I just soak them good for a minute or two, wash out with very light pressure and then as stated above bake them in the sun.

Hope this helps


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## MBrhythm (Mar 1, 2007)

Making the screens are the hardest thing (at first) to do. Once you get your exposure times down, you'll be on your way in making a great shirt.

I wasted five screen by not post-curing. It pays to take the extra time to cure and re-cure.


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## EasyTeesK (Nov 28, 2007)

Check out the information from my post: 

http://www.t-shirtforums.com/screen-printing/t54546.html

I am having this same issue. I haven't tried any of the suggestions, yet (time is an issue having a full-time job).

Kevin


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## AbbieRoad (Feb 24, 2007)

I degreased them pretty well I thought, and washed them out. I put them on the screen printing thing to dry so they're not touching anything else and are suspended in the air. 

I'd thought maybe if there's too much emulsion in that one spot, maybe I should only coat one side of the screen or something? I'd heard from people on Etsy to just do the one side. I don't know. 

How much longer should I expose it? Another 2-3 minutes?


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## MBrhythm (Mar 1, 2007)

AbbieRoad said:


> I degreased them pretty well I thought, and washed them out. I put them on the screen printing thing to dry so they're not touching anything else and are suspended in the air.
> 
> I'd thought maybe if there's too much emulsion in that one spot, maybe I should only coat one side of the screen or something? I'd heard from people on Etsy to just do the one side. I don't know.
> 
> How much longer should I expose it? Another 2-3 minutes?


search for "step-wedge"

Learn the time of _your_ emulsion and _your_ exposure unit by the the WEDGE!


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## macmiller (Jul 23, 2007)

is the gummy part where your scoop coater overlaps to coat the entire screen? if so then that's probably your problem. that would explain the rest of the screen coming out fine. your exposure time is pretty close id' bet, it's just that the emulsion is 2x thick right there and needs close to 2x the exposure time. so you either have to underexpose the thick part or over expose the thin part, either way will be tough to get perfect.

try finding a scoop coater that is about 1.5 inches narrower than the inside of your screens, you'll then be able to coat in one pass.

as far as coating my technique is; thick coat on print side, thick coat on ink side, scrape print side, scrape ink side, dry flat w/ ink side up.

Like MBrythm said, once you get exposing screens nailed, it's pretty easy after that.

good luck!!


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## out da box (May 1, 2007)

Stencil thickness may not be uniform, humidity may be too high, also it looks like there's light undercutting on the edges of your letters in the photo. Do you use a vacuum to perfectly seal your positive to the screen?


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## AbbieRoad (Feb 24, 2007)

yes, it could be stencil thickness. I'm printing on 8x11 transparencies, and to make them dark enough I have to print 2 and tape them together. Without that, it won't pick up fine lines. 

I'm just using a normal exposure unit, no vacuum, just the run of the mill ones from ryonet like this one: 
Aluminum 8 Bulb 240 Watt 25x36" Automated UV Exposure Unit

I do cover it in a piece of felt, then I lay a piece of wood on top and weigh it down with heavy stuff on top though, to make sure it's flush


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## MBrhythm (Mar 1, 2007)

I had the same problem about a year ago when i first started out. My exposure time wasnt right. It was under exposed. My screens looked like the picture you posted. 

Waste a screen on the step/wedge test to see where you should be. Remember everyone's exposure unit is different. What works for me may not work for you.

How to Determine correct screen exposure times using Vellum


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