# Slimy screens...Underexposure?



## vanderz (Oct 27, 2012)

This is my first to t-shirtforums, so first all all Hello to everyone.

I am new to screen printing, well new to the processes of setting up screen and burning my own images. 

I burnt my first screens last night, the image came out really nice sharp clean lines. 

The only problems i came across was, when washing out the screens. If i applied water to the 'Ink side' of the screen, a slimey substance starts to run down the screen. I guess this is the emulsions being thinned down.
And when i cleaned my screens off with soapy water, as i was going to use them again, the emulsion started to rub of in certain areas. 

My question is is this from just from under exposure?

I did originally coat the screens about a month and half ago but never got the time to use them. They have been kept in complete darkness until yesterday, could this have affected it any way? 

Also how long does sensitized emulsion last for? I'm using AZOCOL Z and I'm storing it in a fridge. 

Cheers,
James


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## sben763 (May 17, 2009)

First don't use soap after washout. You need to use proper screen chemical most soaps have chemicals that will attack emulsion. If the emulsion is slimy at washout very probable that they are under exposed. Your emulsion appears to be photopolymer. Did you add diazo? If diazo is added the 90 days and you may start havering issues but I have had it last 8 months. Most photopolymers have a 1 year plus life. The only issues you may run into when coating and let sit is if the humidity get high you will have to run a fan and lower the humidity to make sure the emuslsion isn't holding the humidity. This can cause screen to act like its under exposed.


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## kevinsme2005 (Jul 26, 2011)

I would agree and stress the importance of making sure your screens are properly cleaned. A good degrease and rise is extremely important. I have had the same struggles with getting a good burn on a screen. It wasn't just one fix though.

A properly degreased screen is very important. Follow that up with properly mixed, non expired emulsion evenly coated. Be sure that emulsion isn't prematurely exposed, and get a dehumidifier. Then worry about exposure time last. No use fighting exposure times if you havent got the first part right.

Took me a while to figure it all out, and starting from the first step and working one issue at a time was key. Now I can clean, coat, expose, and print a screen in under two hours. Used to be two days!


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## vanderz (Oct 27, 2012)

Just so you know I'm doing this at hobbyist level. For non profit causes. 



sben763 said:


> Did you add diazo? If diazo is added the 90 days and you may start havering issues but I have had it last 8 months. Most photo polymers have a 1 year plus life.


Yes i added diazo...When i next buy an emulsion would i be better of buying a photopolmers. Is there a big difference other than shelf life? 

Also When drying my emulsion, The screens are stacked on each other with 2x 4 in between each on so the air can flow through each one. Whilst drying i have a Fan and heater on low, to help with drying times and circulation of air. Is this the best way?


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## TshirtStan (May 4, 2008)

In my experience I have to agree with Ben. Moisture in the screens is what it sounds like to me. Either store them in a closet inside or buy a dehumidifier.


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## vanderz (Oct 27, 2012)

kevinsme2005 said:


> I would agree and stress the importance of making sure your screens are properly cleaned. A good degrease and rise is extremely important.


I was told that a strong washing up liquid mix would be good enough to degrease a reclaimed screen. Is this not true could you advise me on which degreaser to buy..?

Also you say about expired emulsion, how do you know when your emulsion is no longer any good too use? 

Cheers
James


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## sben763 (May 17, 2009)

For a cheap sub for degreaser buy simple green original formula. Mix about 8:1 or 10:1 with water. its all the degreaser you need. Rinse well. If you have hard water I use a shop vac (bought specifically for this so its not dirty) I blow off as much water as possible. then into dryer. Once the you expose screen don't use anything but a product for cleaning ink Like screen wash Or Citra-Paste and my favorite Franmar BeanEdoo.

Photopolymer are fast exposing with a less forgiving latitude of exposure time. They are harder to work with at first but it is a must that you get a exposure calculator $11 at Ryonet and get solid 7 and then you can expose anything. I was 5-7 min with dual cure like your using depending on mesh and coating technique. With photopolymer 45sec-2 min Depending on brand and screen mesh. 

drying procedure sounds good. Are you drying in a air conditioned space or a garage or other space where high Humidity can affect proper drying. If humidity is too high the screen will be dry but the humidity can reside in the emulsion. You can do and store screens this way but a 1-2 hour time with a dehumidifier and a fan for circulation in a closet before exposure will ensure proper drying. 

diazo expires when it doesn't expose or that takes much longer to expose. If you humidity is correct and you start getting under exposed screens bump up your time diazo looses sensitivity as it ages. If it takes extra minute then time to change. Wouldn't know with photopolymer never had a gallon go past expire date or quit working like the dual cure. Note if you are doing water base then there are very few pure photopolymer emulsion that stand up. Saati textile PV will do both plastisol and water base with Post exposure and if I remember right you can add diazo to make it discharge compatible. Last time I bought a gallon and split into qts. spit diazo in 4 equal amounts then only mixed water to diazo and then to emulsion as needed but you have to be precise when dividing diazo. They also sell it in individual bottles for quarts but is supplied for free upon request. I was using a rebranded ver of this emulsion


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## vanderz (Oct 27, 2012)

I bought a Stouffer sensitivity guide, i got a solid seven on it at a time of 5mins. But the ink side is still slimey.

Could this be down to the emulsion being applied to thick? I think i put 2 coats on each side, on those screens as i was advised!

I currently expose my screens in a built in wardrobe in my room. So i don't think i have a problem with humidity. I'm going to buy a humidity sensor this week, to to make sure. 

In the mean time, I'm going to coat my screens again and do a ten step exposure on a screen with an detailed image on next time. See how that pans out.

If i use a dehumidifier will something like this be ok? 

Dehumidifier 500ml 1500ml Portable Mini Air for Car / Home, Mains or 12V Adapter | eBay

I think ill stick with the dual core then for the minute. Seems like you need to be much more precise with the Photopolymer's. Plus all my inks are waterbased so it looks like i cant anyway?

What kind of light source do you use to expose your screens? 

I think next time i buy the emulsions ill do that, split it into smaller quantities saves on waste then. 

Thank you very much for the detailed and informative response, looks like there is alot i need to learn.


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## kklowell (Oct 7, 2012)

I just bought a used 40 pint dehumidifier from someone on Craigslist for $20. There were several listed between $25 and $45 too.


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## outbreak (Jan 9, 2010)

Put it out in the sun when after you've exposed it and rinsed it out.


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