11948Re: [PPLetterpress] Re: Photopolymer separating from polyester backer
- Aug 1, 2010You're using all the right equipment and materials. The details on your plate are likely detaching because they haven't received enough light during the main exposure. The photopolymer material hasn't hardened all the way down to the base. It separates during drying while it contracts--it has nothing to hold on with.The bulbs most likely need replacing on your machine as you've surmised. In the meantime you may have to keep increasing your main exposure to compensate for their lack of output. Have you done a Stouffer test at the edge of your bulbs recently? Fluorescent tubes put out less and less light as they age. But you already knew this. Is this what you're asking?HaroldOn Mon, Aug 2, 2010 at 12:47 AM, idgradstudent <glenwoodemorris@...> wrote:
I'm using an older Jet A3 platemaker with analog controls (as opposed to the newer ones with digital controls).
It uses a bank of lights.
The separation is happening at some point between post-washout rinsing and the end of post-exposure. It is not 100% consistent but I will be examining more closely between drying and post-exposure in the future.
I am using silver emulsion film, yes.
Oslo Press Inc.
--- In PPLetterpress@yahoogroups.com, Harold Kyle <harold@...> wrote:> On Sun, Aug 1, 2010 at 11:09 PM, idgradstudent <glenwoodemorris@...>wrote:
> 5 minutes shouldn't be too long for the washout. You're fine there.
> What type of platemaker do you use? Point light source or a bank of lights?
> The photopolymer will separate for lots of reasons. It sounds like this is
> happening during processing? During washout or during drying?
> Finally, are you using silver emulsion film? It sounds like you are. Just
> Would love to help but need more info.
>> > --- In PPLetterpress@yahoogroups.com <PPLetterpress%40yahoogroups.com>,
> > More info:
> > Fresh KF95 plates.
> > I have a lot of "variables" like oldish brushes, and older bulbs that
> > require a long exposure time (9 minutes according to my stouefer scale). So
> > it would certainly be easy to dismiss my issues by saying "Hey, go do some
> > basic maintenance to your platemaker" and you would be right. Aside from
> > this relatively recent issue the plates have been good so I have opted to
> > spend funds on other more pressing issues as a longer exposure time does not
> > cost me much since I only make plates for myself and the cost for new bulbs
> > and ballasts is not insignificant.
> > My washout is probably too long (5 minutes), I will back it off and see if
> > that works. When I first acquired the machine I established my exposure
> > times with a scale and my washout times through trial and error but I may
> > have just gone too far. Generally if I lose anything to this problem it is a
> > crop mark on the edge of a plate, but recently I started losing thin script
> > text and fine lines in graphics if they were also near the edge of the
> > plate.
> > My question included limited info as I wanted to know what the root cause
> > of photopolymer/polyester separation was rather than have folks just tell me
> > to do maintenance that is not really an option right now.
> > Glenwood Morris
> > Oslo Press Inc.
> > "idgradstudent" <glenwoodemorris@> wrote:
> > >
> > > I did some searching and found several discussions about plates that have
> > separated; i.e. the photopolymer has detached from the polyester backer.
> > >
> > > What I did not find in the discussion was any agreed upon conclusions
> > about why exactly this happens (or I simply missed it).
> > >
> > > Does anyone know what causes this to occur? I am currently having
> > problems with this with some of my plates and was wondering if there was a
> > "known cause" before I just start changing things and hoping for the best.
> > >
> > > Thanks,
> > >
> > > Glenwood Morris
> > >
> > > Oslo Press Inc.
> > >
> Boxcar Press
> 501 W. Fayette St. #222
> Syracuse, NY 13204
501 W. Fayette St. #222
Syracuse, NY 13204
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