Plate Developing Problems

[peewee]

Hi guys,

I trained years ago on a GTO 46 but been out of it for years. Trying to set up a small shop but having problems developing plates for my Rotaprint SRA4 machine.

I'm exposing aluminium posi plates to UV light for 2 minutes using a professional unit with new bulbs. Longer than this seems to leak around the film though I'm using a vacuum unit. The plates seem to image well, they are green coating to start with turning blue when exposed. I'm using a general clear metasilicate developer solution but I find using a sponge the imaged area soon comes off too! If I just leave it to soak for a while the plate bubbles and yet just a quick wash doesn't seem to take anything off.

What am I doing wrong? As far as I remember I'm doing this right?

Thanks,

Peewee

 

[maxon]

You should use the proper developer for the plates you have. For screened images you may also want to calibrate the exposure time to obtain the correct raster percentage, use a stouffer wedge.

 

[vniehaus]

2 minutes is a long time. I do 10 seconds. Are plate developer broke so right now were cleaning by hand with no problems. We don't do very much printing anymore anyway.

 

[vniehaus]

You need the right developer. I just use Universal plate developer and finish it off with gum.

 

[WS@Fujifilm]

Some wrong statements:

aluminium posi plates -> the imaged area soon comes off too!

If the imaged area goes OFF - this is correct as you use a positive plate
if the non imaged are is gone, means the text you like to print (when using pos-film & pos-plates) the developer is is not compatible with your plate
The coating at a positive plate is "damaged" by the UV-light. The non-exposed are is remaining after developing. Means that the removal of your text has nothing to do with exposure time - just wrong combination of plate & developer.

Visit a local graph-art dealer and ask for a proven combination form one of the major players

Cheers

Wieland

 

[farhad azizi]

Positive plate

Positive plate

It seems you may faced 3 problems,
1- The new bulb too powerful.
2- The exposure time too long.
3- The developer too strong.
4- The contact film is not 100% black
suggestions:
a: expose one minute and do developing as did before.
b: dilute your developer with more water.
c: check film contrast with a densitometer.
Hope my suggestions helpful
farhad

 

[peewee]

Guys,

Thanks for comments - really helpful. The label on the box lead me to believe the plates were posh but as you guys guessed, they were negative so I had the wrong combination. So glad you can't se my blushing cheeks.

Thanks.

peewee