Re: [PPLetterpress] Re: Jagged Lines and poor letter detail on plates
- Hi Matthew,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 negative.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 negative.Best wishes, TomTom Parson/ Now It's Up To You
157 S Logan, Denver CO 80209
(303) 777-8951 - home & letterpress printshop
(720) 480-5358 - cranky cellphone
www.froglok.com/typetom (way out of date website!)In a message dated 7/6/2010 8:12:09 A.M. Mountain Daylight Time, mlen13@... writes:
Thanks 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 the plate.
Thanks in advance for any help!
--- In PPLetterpress@yahoogroups.com, "Eric" <Megalonyx@...> wrote:
> 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. 9177969143
> --Eric Holub, SF
- Definitely use a scale, we use a Stouffer Scale and for your thickness of plate the exposure value will be shown on the package or in the plate's insert. Your plate merchant should be able to supply one.
I think, too, that "luke warm" is a good indicator of a problem. Your water should be around 23 degrees C.or 73 degrees F. Any warmer and you're really going to undercut the letters.
As far as washing out by hand, we use (for touch ups) a baby hair brush or a really soft fingernail brush and use a swirling motion over the washout area. Swirling clockwise and then counter clockwise to even out the contact. Again I think you may be over washing out, if you don't follow the manufacturers instructions trouble is sure to follow.
You're welcome to send me a sample and I'll take a look at it. Contact me through our website.
--- In PPLetterpress@yahoogroups.com, "mlen13" <mlen13@...> wrote:
> Thanks 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 the plate.
> Thanks in advance for any help!
> --- In PPLetterpress@yahoogroups.com, "Eric" <Megalonyx@> wrote:
> > 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. 9177969143
> > --Eric Holub, SF