Rough finish on PP plates
Hello everyone,
I am trying to make my first photopolymer plate and as expected it was not going to be easy.
The plate seems fine except for a “rough finish” on some areas. The base of the plate, where there is no image/type, has a couple of scratches too.
Has this happened to you? what do you think causes this?
I am thinking it could be that the washout was too long. However the plate still felt sticky in some areas and therefore i put it back on the washout for about 80 more seconds (20 sec at a time) until the plate had no tackiness.
I bought the platemaker used and was told the bushes are still in good condition but there are areas that feel quite rough. I have tried washing them with hot water and they are a lot better. Can this be causing the rough finish on the plate?
Platemaker is an Inglese 43E, i am using film-backed miraclon DF94, darkroom, tested exposure to step 15,
any comments appreciated. Leo
The brushes should absolutely not feel rough. You could need a new brush if it feels rough in places. The way to check if these are affecting plate processing is to process a plate again and pay special attention to the location of any marks on the plate; see if they correspond with rough spots on the brush.
I’ve not heard of anything that can be done to soften one of these brushes once polymer has hardened on it, so contact the manufacturer and quote out a new brush.
Slightly contaminated brushes can be brought back with the use of a metal comb. the kind used to clean painter’s brushes. Try soaking beforehand with warm water and some added vinegar.
For brushes to scratch the base of the plate, they would have to be in very bad condition. And by the time they’s scratched the base, they’d already have done quite a job on the image.
lishii
The only time I have heard of this problem is when the bath level was too low. Probably a quarter of an inch above the brushes is best.
Eric’s comments about the brush are correct. Note though that once the floor of the brush plate is contaminated with hardened polymer and the tufts are caught in this, it won’t be long before that brush is on the road home.
Generally, when buying a used machine it is good practice to check out the condition of the ballasts, replace all the bulbs, replace the brush unit.
This January during the short lull, I had the ballasts and their wiring all checked out, replaced all the bulbs, and put in a new brush even though the old brush was not yet shot.
Feels like a brand new machine.
A little tip regarding Kreene, replace it if gets scratched, had any amount of dirt stuck to it, no longer seals correctly without a great deal of manipulation. Replacing this one single item on a very regular basis will save you so much time.
Gerald
http://BielerPress.blogspot.com
lishii
A further note here. You might want to check out the PPLetterpress list:
http://groups.yahoo.com/group/PPLetterpress/
I founded this back in 2001 to provide a community forum on letterpress printing with photopolymer plates. Seems like most of the die hard photopolymer plate folks are there.
Gerald
Thank you so much guys sharing a bit of your trade secrets.
I will definately try the vinegar and the brush-cleaner. I am hopeful that at least i can save 2-3 of the 8 brushes. New ones are $1300. I might be able to use the machine with only 3 brushes. Mind you, each brush is about 100x800 so i should still be able to make my normal size plates with room to spare. Yes i know, the machine is a bit of an overkill for my purposes but it seemed a bargain at $1000.
I can almost hear you, Gerald, - you should have kept ordering you plates from your reliable processor!!
yep…
lishii
If I would have done that you would not be here.