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Hi everyone :)

I DESPERATELY NEED YOUR HELP! I've read through tons of posts & a bunch of my questions have been answered, but I need some me-specific assistance.

I'm in the process of starting up a t-shirt company. In June 2010, I purchased a Chaparral 4x4 manual press, a Ryonet flash dryer, & a large exposure unit from a home printer in NJ, all pieces were used. I also bought a bunch of pre-used screens from him that needed a lot of cleaning. At the time, I didn't have emulsion remover & used a bleach/water mixture to clean them, most came out fine.

I converted my small basement into a studio. The basement is separated by the staircase & I decided to make the smaller side into a darkroom. I blacked out the 4 small windows w/ black spray paint. I used a single 60 watt bug light for my light & coated a few of the screens with 2 different emulsions...some w/ Speedball Diazo Photo Emulsion (that was ordered in March 2010 and kept in the refrigerator) & some w/ Screen Printing Superstore's EX1 (that I had just bought, mixed properly, & now store in the refrigerator.)

I used a scoop coater to evenly spread the emulsion on both sides of the screens & left them standing vertically to dry with all lights off. I came back a few hours later & exposed them using some older acetate designs (that had worked before, taped w/ clear tape to the t-shirt side of the screen & placed on top of the exposure unit's glass) for 3 minutes (the exposure unit's previous owner told me 3 mins was his perfect time & I decided to start there.)

After they were exposed, I brought them outside to wash with the hose & the 1 w/ the Speedball emulsion came out a little & the EX1 hardly worked at all. I assumed my exposure time was probably different than his since I was using different emulsions under different conditions.

I tried 4 minutes, 5, 7, 8, 9, 15...nothing. It took me days to figure out what was going wrong. I had forgotten to assemble the top of the exposure unit, the part that keeps all the light in (& would vacuum seal it if I could figure out how to hook up the suction ha). Well that was an easy fix & I thought for sure it would all work.

I coated my screens w/ the EX1 (b/c I know there's nothing wrong w/ it), let them dry for a few hours, made some new designs using blick .005" acetate & Staedtler permanent lumocolor pens & acrylic paint, & attempted to expose them again for 3 mins. 1 of 2 came out, but the edges were fuzzy so I took that as the screen wasn't fully dry. Coated a couple more screens, put a fan on them to dry, waited a good 6 hours, exposed for 4 minutes...nothing.

This made me think the screens were getting pre-exposed somehow. I changed the bug light to a red 60 watt bulb. The only light that could be entering is when the door at the top of the stairs is opened and closed when I enter the basement, but this is for a few secs. I tried to expose again & as always...nothing.

I am now washing the screens w/ CCI ER/35 (50% water, 50% chemical), I let them dry, then coat them w/ emulsion.

:confused:WHAT AM I DOING WRONG??!?!?!?!?!?!?:confused:

I am buying dehazer and degreaser tomorrow (do I need to?), I got a few screens remeshed in case the bleach/being used ruined them, but those are the only factors I could think of. PLEASE HELP ME!!! ALL comments, answers, suggestions would be much appreciated!

THANKS!!!!
-Samantha
 

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Hi,
Welcome to the wonderful world of screenprinting. Where everything that can go wrong, will go wrong until you get full control of all parameters. The good thing is there are tools to help you figure out what's going on. First thing you will need to get is a 21 step exposure calculator. All it is is a small film with 21 diifernt shades of black. It will help you determine your exact time needed. Also be careful that you are not continuing to exposexpose when you take the screens outside to wash out. Oh and dry horizontal, not verticle.
 

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Outside, as in the sun? 30 seconds of direct sunlight fully exposes any emulsion. Even indirect sunlight, like on a cloudy day, can cure them to the point they won't was out properly. You can handle exposed screens in normal room light for a reasonable time, but not the sun. See the article above about different methods of washing out screens with taking them outside. God Bless.
 

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Discussion Starter #5
Hmm...all very helpful advice. I got the sink fixed in the basement and will be washing the screens out inside now. And I'm going to try the whole step test again now that my screens should be exposing properly.

THANKS EVERYONE!!!

I'll be sure to post my results.
 

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Keeping your coated screens out of the sun is very important...Also you need to figure out the exposure time that will work with your emulsion and the exposure unit you are using. If i may also suggest NOT placing your freshly coated screen vertically. Maybe build a small rack to keep them horizontal so that your emulsion dries evenly and place them print side down.
 

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Discussion Starter #7
So I coated my screens, dried them VERTICALLY, and used one for a STEP TEST from 1-5 minutes basing my times on what the previous owner had told me his was (3 mins). The only time that came out was 1 min after I washed the screen INSIDE. So I did another at 15 second intervals and only 15 seconds came out. After a little bit of trail and error, I came to the conclusion that my exposure time is 16 seconds (that's quite different from 3 mins!) and I now have my first perfect stencil!

THANKS AGAIN!!!!!

Also, if I don't change any of the factors (emulsion, exposure unit, etc), will all my screens always expose at 16 seconds?
 

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Back to drying the screens vertically. This may not make any appreciable difference with type and simple artwork with no fine detail, but as you get into more detailed work and halftones, you will find that there are areas of the screen where the emulsion is thicker or thinner, which will cause uneven exposure. Also, if the screen is simply lying on the glass, you will probably not get good enough contact for detailed designs. That's why a vacuum frame is so important. A piece of sponge to fit inside the screen with a weighted board on top will help.
 

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Discussion Starter #9
On the one screen that I exposed, I did notice that some of the detail wasn't as clear as I had hoped. Right now I'm working with a T-Rex design that has pretty detailed skin/scales; there are a lot of small marks. A few scales didn't come out where the emulsion was thicker down the middle of the screen. The screen is about 16" wide and my scoop coater is 10", so my coats overlap in the middle. Should I buy a larger scoop coater? Or is there a way to prevent the middle from being thicker?

Also, my exposure unit DOES have a vacuum frame. The previous owner never figured out how to use it/get it to work, so he never bothered with it, his screens came out fine, and he told me I didn't need it. My screen printing professor used one, but I never really knew it's purpose. So I should look into getting it hooked up? I'll get better results as far as detail exposing correctly goes?
 

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I wider scoop coater will make coating screens easier.. You vaccum top will make a huge difference. I used to expose my screen foam and a weight and my screens came out pretty good.. And once I added a vaccum lid the difference in detail was amazing.
 
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