Plates Catching small dots of ink

Hi,
I'm having problem with printing plates during stoppages... All the plates catch small dots on the entire non image area even if the press is stopped for less then 30 sec....
we have to wash the plates every time after these stoppages......
need your help.....

 

Oxidation, change plates and chemistry or use 5% phosphoric acid to clean or it could be too much Alcohol if you use Alcohol that is, and it's solving the ink

 

souns like a lack of fount is you aks me

 

we have changed the plates but same problem...and we changed the fount but still the problem is there, Alcohol may b the problem, but I'm not sure what to do, increase or decrease......

 

i agree with rolandman about it being a problem with fountain solution. Ive found that on some papers the paper dust will sensitize the plate enough to cause the spots in non image area you describe. Have you noticed this happening more in the first color your printing on a multicolor press? Its usually the first color that gets the largest amount of paper dust via the blanket. Ive also had success with running 2 different mixes of fountain solution. I run a dedicated formula thats mixed a bit stronger when running certain uncoated papers that have a tendency to cause these spots you speak of. If your having this issue on all your jobs then id suggest a bit more fount.

 

How's the conductivity of your fount - is your incoming water supply clean and free of contaminants?

But then I suppose it depends on how long the stoppage is and what the temp / rh is in the pressroom (hmmm, you're in Karachi...could be pretty warm is my guess) ...but you could try squirting a bead of gum across your dampeners once you've stopped printing and then lifting the dampeners off to allow the gum to dry...just don't over do it or you'll probably get foaming from the gum running into the water system.

 

@TT.... It is happening more in the 6th printing unit and also in 3rd and 2nd... one thing I've noticed is that this problem is more related with magenta and cyan and any tone of blue, like bronze blue or ultramarine..... but I'm not sure...
@Richardk.... yes the temperature in karachi in these months remains around 40C....
We have called a new fount supplier and let's see what happens now....

 

I'm adding 3% of fount and if I increase the fount then I m facing problem of too much foaming....

 

3% sounds about right are you using a doser? if so make sure it is actually dosing the ammount it is set to

 

No we are mixing manually......