# emulsion not hardening



## mindye (Nov 19, 2009)

help..........my emulsion is falling off my screen,after i dried and expose the screen when washing screen for the stencil everything fall apart......what i'm i doing wrong?????
thanks guys


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## PositiveDave (Dec 1, 2008)

Did it dissolve away (i.e. it isn't cured) or fall off in sheets (it has cured but hasn't stuck).
It's probably your emulsion not curing, is it a two part (have you added the crosslinker), how old is it?
It could be your uv source, has it worked before? How old is it - they deteriorate?


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## mindye (Nov 19, 2009)

It's just over 2 months old and yes i did mixed it,is it cuz it's expired????.....i've just ordered the ''all in 1 emulsion'' which was said to last for a year or a year and a half.Do you recomend it?


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## PositiveDave (Dec 1, 2008)

mindye said:


> It's just over 2 months old and yes i did mixed it,is it cuz it's expired????.....i've just ordered the ''all in 1 emulsion'' which was said to last for a year or a year and a half.Do you recomend it?


It's just a possibility, one should eliminate each possibility systematically. 
It could just be your exposure time?


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## Rexx (Aug 13, 2009)

Could his screen have been dirty? Like he didnt degrease it before applying


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## Uncle John (Mar 11, 2007)

Sounds like the screen was not clean and degrease properly. If that's the case emulsion won't hold on to the screen. Make sure you follow the instructions that come with the chemicals, this can also cause fish eyes in the screen.
Hope it helps, John


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## RichardGreaves (Nov 7, 2006)

The purpose of exposure is to change the stencil from something that will dissolve with water to something that won't dissolve with water. If it breaks down - it's exposure.

As PositiveDave brought up, I think you are only partially curing your stencil - under cure. If you completely cured the stencil, it wouldn't come off. The proof is in the result.

Screen makers can only expose from one side of the screen. UV energy has to move through the stencil all the way to the inside of the screen. When under exposed, the inside of the screen dissolves with water and the hardened bottom surface of the stencil can peel away from the mesh.

With lamps that are poor emitters of UV-A energy, exposure can take longer than an hour.

Diazo emulsion is slower than pre-sensitized emulsion and does lose stability after 4-6 weeks.

*Degreasing is not so important for Direct Emulsion*
When you have adhesion problems, I wouldn't focus on degreasing either. When you coat mesh with direct emulsion, nasty dirt or oil is simply trapped inside and can't really do any harm.

If I put oil on your arms and then encapsulate your wrist with a watch band or hand-cuffs, they won't come off when you pull on them no matter how dirty they are.


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## nativeera (Jun 4, 2009)

Exposure Time is incorrect and not depending on your light source as well.


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## RichardGreaves (Nov 7, 2006)

nativeera said:


> Exposure Time is incorrect and not depending on your light source as well.


What does this mean?

I understand "Exposure Time is incorrect", what is your point about the light source?


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## nativeera (Jun 4, 2009)

RichardGreaves said:


> What does this mean?
> 
> I understand "Exposure Time is incorrect", what is your point about the light source?


 it means: your light source.. what kind of light source are you using.. and what ever it is, it will determine how much exposure time you need... 500 watt light placed about 1 ft away from the image to expose, will be and again depending on your emulsion, will take approx.. 8 1/2 mins.... that is my time and it's perfect every time....


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## PositiveDave (Dec 1, 2008)

1" !!!!!!!
You are probably heat curing 

Rule of thumb is that your exposure distance should be about the same as your screen diagonal. So if you have a 20x20" screen (50x50cm for our younger listeners), start with an exposure distance of 28-30", about 75cm.

If you are too close then your exposure may be uneven and you will get undercutting.
As you increase the distance you will need to increase the time, there's an inverse square law - it isn't linear, double the distance quadrupal the time.
If your time is excessive you might want to look at the uv output of your lamp, domestic lamps are usually screened for uv - it's considered a bad thing to fry your retinas. Exposure lamps are tuned to emit at the right wavelength.


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