# Starting to lose the will with exposing my screens.



## Merrony2016 (Jan 21, 2017)

So I've done a step wedge test, twice. Both resulting in a 9:30minute exposure using a two part emulsion. The issue I'm having is that once I then go and create my screen, and expose it at 930, it doesn't wash out!? but it washes out on the wedge test? with no trouble at all. Why is it doing that? I hope it's me just being daft but check out the two images below. Left is after the wedge test. Is mesh count a factor in this? I'm from the UK so, 43T on the left 55T on the right. Surely this shouldn't make a difference.


----------



## AAPrintingWizard (Mar 6, 2017)

From what I gather it looks like this is a problem with your exposure system, what are you using as a light source?


----------



## Merrony2016 (Jan 21, 2017)

AAPrintingWizard said:


> From what I gather it looks like this is a problem with your exposure system, what are you using as a light source?


 It's a UV exposure unit?


----------



## PatWibble (Mar 7, 2014)

What emulsion are you using?
How long have you had it sensitised?
Did you make sure it was fully dry before exposing?
Is your workshop/drying cabinet damp or humid?
What lamp are you using?
How close to the screen is the lamp?

Mesh count makes a small difference, but not much between 43 and 55t.


----------



## Merrony2016 (Jan 21, 2017)

PatWibble said:


> What emulsion are you using?
> How long have you had it sensitised?
> Did you make sure it was fully dry before exposing?
> Is your workshop/drying cabinet damp or humid?
> ...


I'm using 2 part emulsion, that's all it says on the tub. It came in the package I purchased.
It's been sensitised for about 3 weeks now, stored in the dark room.
It was dry yeah and my dark room/cabinet is dry, got a dehumidifier in there. I'm using an exposure unit, so flat top glass on UV lights.
The image below is my make shift stepwedge.
Would anyone suggest going to Photopolymer?


----------



## PatWibble (Mar 7, 2014)

It looks to me like either the emulsion is coming to the end of its shelf life or the screen wasn't fully dry before you exposed. 
What brand is the exposure unit? What exposure time do they recommend?

Try re making the screens - degrease them first by rubbing over with meths. 
Allow to dry _completely_ - put a small fan heater in the cabinet to help, but leave some ventilation.

Do another step test, but go up to 12 mins to see if it makes a difference.

If it still doesn't work, drink the rest of the meths. ( Joke)


----------



## Merrony2016 (Jan 21, 2017)

PatWibble said:


> It looks to me like either the emulsion is coming to the end of its shelf life or the screen wasn't fully dry before you exposed.
> What brand is the exposure unit? What exposure time do they recommend?
> 
> Try re making the screens - degrease them first by rubbing over with meths.
> ...


The emulsion was brand new as i had to sensitise it myself. Alrighty, I'll check in tomorrow with all of this stuff.. gotta get some ice for the Meths haha


----------



## PatWibble (Mar 7, 2014)

Merrony2016 said:


> The emulsion was brand new as i had to sensitise it myself.


Once sensitised some emulsion doesn't last much more than a month, and needs to be kept cool, preferably in the fridge. If it hadn't been stored properly by the seller then it can have a very short shelf life.
Don't know who you bought it from, but I have had emulsion from Wicked Printing Stuff in the past that was useless from the start.


----------



## Printor (Apr 16, 2015)

I noticed that when ever the topic of step tests comes up on TSF, no one ever takes into account that the test is being done with the perfect opaque film the step test was printed with, and then most printers are printing their film with a much less opaque system. Create or download a test strip and print it with your film, then test, and that will tell you whats best for your combination of variables. I think you will find you have to under expose to the workable limit with your film.....................add on.... I missed the pic of your step test method. Is it a vacuum unit, if not are you sure your film is flat against the screen enough?


----------



## Merrony2016 (Jan 21, 2017)

Printor said:


> I noticed that when ever the topic of step tests comes up on TSF, no one ever takes into account that the test is being done with the perfect opaque film the step test was printed with, and then most printers are printing their film with a much less opaque system. Create or download a test strip and print it with your film, then test, and that will tell you whats best for your combination of variables. I think you will find you have to under expose to the workable limit with your film.
> 
> 
> 
> ...


Okay cool, I'll do a bit of research on creating my own one. It isn't a vacuum unit no but I have the option to install one into it. I've made a make shift board to go on top of the screen to make sure the positive is making contact so the light doesn't creep round haha. I'll keep trying ?Thank you


----------



## Printor (Apr 16, 2015)

Merrony2016 said:


> Okay cool, I'll do a bit of research on creating my own one. It isn't a vacuum unit no but I have the option to install one into it. I've made a make shift board to go on top of the screen to make sure the positive is making contact so the light doesn't creep round haha. I'll keep trying ?Thank you


 Make sure there is some weight on it but not enough to flex the glass. you want something flat black and preferably soft between your board and the screen to soak up light that gets past the film. a few black test pellons, a black t/no seems, thin piece of foam rubber, are some things that work in a pinch.


----------

