Eric's brief summary of the kinds of problems and results is excellent.
Your description of the problem(s) is still somewhat unclear to
me, suggesting contradictory factors.
Your initial email said you do 4-6 minute exposure. That may explain
any filling in and possibly additional swelling around the edges of the letters.
I use Miraclon MS152 (Steel-backed) plates with about a 2 minute exposure
time. 4-6 minutes for me definitely would fill and swell the base/substrate
polymer enough to distort the letters.
The description of "jagged lines" or "jagged edges" is confusing me because
it could describe several different situations: pixilated type in the file
itself; a negative that is not opaque enough; excessive time in the washout
(which might loosen the surface polymer image from the base and allow lines to
become distorted or broken). Poor contact would probably cause irregularly
swollen letters rather than jagged letters.
(I had inconsistent contact and irregularly swollen letters using a vacuum
frame with a glass top (no kreen) until I added pieces of matboard around the
plate material to support the glass, which I think was actually bending from the
vacuum! Problem solved completely since I added matboard pieces
inside the frame.)
Pixilated type is often a problem for me with files others send. The font
needs to be embedded, or attached so it can be installed, or the font
needs to be saved as an outline (eg. Illustrator). I still don't fully
understand digital terminology, cause and effect, but it's easy to check by
enlarging the image on screen to 400 or 600%. If the font does not have smooth
curves as it is enlarged, the lines will be jagged in the plate! Another source
of this effect is when an image has been resized (eg. Photoshop): if the image
is "re-sampled" when it is enlarged, it will have less resolution and appear
more jagged. These effects are separate from the resolution of the printout or
A sharpie pen and careful, tedious hand-work can improve a weak negative. I
have done successful plates from computer-generated transparencies, but it
required reducing exposure to less than a minute (thus risking any fine lines or
dots that need more exposure for support). And I still have to
wash out unwanted background that has partially exposed anyhow! Toner does
not block UV light adequately. Very short exposure time and a sharpie pen
can help, but it's not worth the effort except in an emergency or for rough
effects. A right-reading emulsion up negative from an Image Setter is the best
answer, and a good service bureau can solve most computer file confusions.
I normally aim for 4 minutes hand washout, try to stop myself
even if there is unexposed material still present, and definitely stop by 7
or 8 minutes (larger plates). Water temperature will speed or retard this. The
goal is to lightly agitate the unexposed polymer material to disperse
it as it dissolves. Aggressive hand-washout becomes more destructive
as the polymer absorbs water and softens from the base up.
Drying time and re-exposure are secondary, mostly affecting the long-term
quality of the finished plate.
The critical factors (besides a good file and a good negative) are the
exposure time, good contact, and the washout time. I am guessing your main
problem is too much exposure, especially if you are using a computer-generate
Best wishes, Tom
Tom Parson/ Now It's Up To You
157 S Logan, Denver CO 80209
777-8951 - home & letterpress printshop
(720) 480-5358 - cranky
(way out of
In a message dated 7/6/2010 8:12:09 A.M. Mountain Daylight Time,
for the replies. I don't think bad contact is the issue as i do have a nice
vacuum seaL, between the kreen, the negative and the plate.
With a 2-3
min exposure and a lukewarm water washout i get the jagged edges or filling
in. I've tried many many variations of exposure/washout times and with
additional exposure and washout i do have letters and detail crumbling off of
Thanks in advance for any help!
--- In PPLetterpress@yahoogroups.com, "Eric" <Megalonyx@...>
> Can you be more specific? Bad contact, over-exposure or
insufficient washout could cause filling in, but under-exposure or excess
washout could cause loss of serifs, broken lines, etc, and incorrect
temperature, or innappropriate brush, could complicate the process.
> --Eric Holub, SF