# Emulsion not being exposed as it should



## shanifee (Oct 20, 2015)

Hi guys,

I'm a beginner in screen printing. Had a few problems with my screens and after searching all over internet and still not being sure what's wrong, I would be happy if you could help.

I am using Ulano 925 emulsion which comes purple and turn to green-brown after sensitized (or so I thought). 
I'm using the sun for exposure. 
*At the moment I am using a low tech techniques - I don't have places to purchase screen printing supply here- and can't seem to find much shops that ships to here..

So here is what I did along the way:
First screen was too thick and under exposed.
I read somewhere that the emulsion should turn to the original color (purple) but it didn't happen with my screen. 

My second screen was after storing the emulsion for 2 months after it is already sensitized (in a cool dark place). I used a LED lamp colored to red as safe light while coating the screen, I read somewhere it should be fine. 
The coats of emulsion was thin and crisp, 1 coat for each side. It dried fast but I had to wait 3 days for a sunny day. For exposure I used a glass on top and cardboard on the bottom - but the cardboard was useless since it didn't block much of the light. I then exposed it to the sun and waited for the emulsion to turn purple (Should it really change color?), again that did not happen. I set there for 40 minutes (!!) and gave up. I saw my image was kinda unseen, but it was there. I tried to wash it off but nothing came off the screen. After washing I noticed the screen was blank! There was only a coat of emulsion with no image! I made an experiment and let the screen dry another 30 minutes in the sun to see of there's any color change but still nothing. 

I tried to reclaim the screen with a remover but it's really hard to wash off and some of the emulsion just won't come off. I know under exposed screens usually acts this way- but really? It was exposed forever!

I know I must did tons of mistakes but I can't seem to spot what exactly was so wrong that the screen acted this way on the second time. I would much appreciate your help!


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## Ripcord (Sep 2, 2006)

You overexposed that screen and that's why it didn't rinse out and why you can't see an image. The sun is intense UV light and an exposure of one minute is about right, more or less depending on the emulsion.


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## shanifee (Oct 20, 2015)

Ripcord said:


> You overexposed that screen and that's why it didn't rinse out and why you can't see an image. The sun is intense UV light and an exposure of one minute is about right, more or less depending on the emulsion.


The first screen was 3.5 minutes of sun exposure and it was under exposed, but on my second screen i really depend on the color changing to the original color since I read it should happen with Ulano 925.

Also read on a few threads that overexposing was not much big of a deal- and that reclaiming an overexposed screen is easier. But I guess my screen was really over exposed.


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## Ripcord (Sep 2, 2006)

shanifee said:


> Also read on a few threads that overexposing was not much big of a deal- and that reclaiming an overexposed screen is easier. But I guess my screen was really over exposed.


Overexposure is certainly preferable than underexposure, but if it's severely overexposed it won't wash out. I've never used Ulano 925 but I can't believe it's so dramatically different than the Ulano Proclaim I use. Do a step test to easily determine the correct exposure, and make sure the sun is full shining, not behind a cloud and don't do it too early in the morning or late in the afternoon.


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## shanifee (Oct 20, 2015)

Ripcord said:


> Overexposure is certainly preferable than underexposure, but if it's severely overexposed it won't wash out. I've never used Ulano 925 but I can't believe it's so dramatically different than the Ulano Proclaim I use. Do a step test to easily determine the correct exposure, and make sure the sun is full shining, not behind a cloud and don't do it too early in the morning or late in the afternoon.


That explains! I won't count on the color changing this time. Thank you!


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