stacastic printing

[printr640]

We have been testing our presses for stacatic printing. How many of you out there are running stacastic and please share any experiances you may have.

 

[gordo]

We have been testing our presses for stacatic printing. How many of you out there are running stacastic and please share any experiances you may have.

To answer you, it would help to have a bit more info.
What sort of printing do you do? (web, sheetfed, commercial, packaging, etc)
What CtP are you using? What workflow/stochastic screening are you using?
What is causing you to consider changing what you are currently using?

best, gordo

 

[printr640]

To answer you, it would help to have a bit more info.
What sort of printing do you do? (web, sheetfed, commercial, packaging, etc)
What CtP are you using? What workflow/stochastic screening are you using?
What is causing you to consider changing what you are currently using?

best, gordo

sheetfed and mostly commercial printing

ctp - trendsetter 8003

workflow - printergy

currently we use 175 line screens

stochastic 20 micron

we have not changed just testing right now. not sure exactly why we are testing this but i think its sales driven, we had a job awhile back a new sales person brought in that was previously printed with stochastic and we could not match it.

 

[gordo]

sheetfed and mostly commercial printing, ctp - trendsetter 8003, workflow - printergy, currently we use 175 line screens, stochastic 20 micron
we have not changed just testing right now. not sure exactly why we are testing this but i think its sales driven, we had a job awhile back a new sales person brought in that was previously printed with stochastic and we could not match it.

OK.
Most of the implementation process will be in prepress - hopefully you have good communication with them. The process is briefly and basically:
1) You must have a reliable, effective, stable printing process in place. I.e. print to the numbers and not using the press as a color correction device.
2) Your plate need to be qualified for the dot size you'll be using. You'll be using Staccato which, for a 20 micron screen, uses a highlight dot size equivalent to a 1.5% dot at 150 lpi with a midtone dot size of 24 microns. It's equivalent to a 385 lpi regular AM screen.
3) You need to speak with your ink vendor to confirm that your current ink set is suitable for such a high frequency screen (pigment load, viscosity, tack, etc.)
4) Prepress will build curves which will be applied to the plates during imaging to compensate for the increased dot gain caused by the use of small dots. To do that they should run a 175 lpi test using your current setup which will become the target for your Staccato presswork. They will than run the test form using uncalibrated plates with Staccato screening. From those two press runs they will have the info needed to build plate curves.
5) They should then go on press with the same test form to confirm their curves.
6) Prepress may update their proofing to reflect the slightly larger color gamut of Staccato.

Some things to note:
FM screens are more stable on press than a 175 lpi AM screen. Color can be moved - but not as fast or in the same tone areas as a 175 lpi.
The gamut/color range is larger - primarily in the quarter and mid tones. That means that one an two color screen tint builds will look different.
You will use slightly less water because the ink film thickness will be slightly lower.
Printers who are successful with this type of screening are so because they are committed to it and use it 100% and only use 175 lpi as the exception.

You might find some of my blog postings helpful. These in particular:
http://qualityinprint.blogspot.com/2009/02/golden-reference-part-one.html
http://qualityinprint.blogspot.com/2009/02/golden-reference-part-2.html
http://qualityinprint.blogspot.com/2008/12/2nd-order-fm-screen.html

Or rummage around my print blog here: Quality In Print

hope this helps, gordo

 

[printr640]

we have our coated curves looking really good for stachastic. today we put on a test with uncoated and it looked really bad; the appearance of it looked like i needed to sqeeze the sheet more. i was sqeezed as far down as i could go. looks to me that a 20 micron dot is not a good choice for an uncoated sheet. we tried 70# cougar opauqe and 70# williamsburg. we used this paper because this is what we print a lot of our uncoated work on.

tried new blankets and overpacking .003 niether helped at all

 

[gordo]

we have our coated curves looking really good for stachastic. today we put on a test with uncoated and it looked really bad; the appearance of it looked like i needed to sqeeze the sheet more. i was sqeezed as far down as i could go. looks to me that a 20 micron dot is not a good choice for an uncoated sheet.

Stochastic (even at 10 micron) is absolutely fine for uncoated. It doesn't sound like you've built proper plate curves for use on uncoated paper though, and that is likely causing your problem.
Just as you should with AM screening, you should have separate plate curves for coated and uncoated paper so that the plates are optimized for the press and that the press can be run in its "sweet spot."

best, gordon p

 

[printr640]

We were in the process of building our curve for uncoated. We started with no curve applied to plates and made our adjustments, we were really close to where we should be in respect to dot gain after adjustments. Over all the color looked decent but we were not laying a uniform dot down onto the subtrate. Like I said in previous post it looked as though I needed to add more pressure to sheet

could our ink and/or water have this affect. i ran a live job for first time today with stochastic with the coated curves. had problems keeping color balanced.

 

[gordo]

We were in the process of building our curve for uncoated. We started with no curve applied to plates and made our adjustments, we were really close to where we should be in respect to dot gain after adjustments. Over all the color looked decent but we were not laying a uniform dot down onto the subtrate. Like I said in previous post it looked as though I needed to add more pressure to sheet
could our ink and/or water have this affect. i ran a live job for first time today with stochastic with the coated curves. had problems keeping color balanced.

Your post is a bit unclear when you say: "We started with no curve applied to plates and made our adjustments, we were really close to where we should be in respect to dot gain after adjustments."
Do you mean you are making new plates using new (adjusted) curves? Or are you adjusting the press?

I can't think of what kind of issue you could have that could be solved by increasing squeeze. That being said, here are some possibilities as to what might be happening:
1) Papers can have variations in ink receptivity across their surface. FM screens, being high resolution, can magnify this issue which can look like splotchy tone areas. If the problem disappears if you go back to 175 lpi or if you switch papers that may be the problem.
2) Poor ink transfer. The ink may be too stiff, or your fountain solution too aggressive. Small FM dots carry a thinner film of ink and can be attacked more readily by the fountain solution, which can result in splotchy looking presswork.

In general, 175 lpi printers are typically well suited to run 20 micron FM with the inks they use for 175 lpi printing. FM inks should have low viscosity and high flow. Low viscosity helps ink shear and transfer to the sheet. You can drop viscosity by changing the pigment vehicle (oil), by increasing the water pickup, or by increasing ink temperature. High-pigment, low-gain inks are problematic with because they have a propensity to print inconsistently. Generally, you don't need to change ink tack values or sequence from those used with AM settings. FM performs best on press when using small levels of water and just enough ink to achieve desired densities. Use water levels rather than ink density to control FM microdots. Adjusting density to control midtones should be the exception and not common practice. Collaborate with your ink manufacturer to optimize performance of FM on your press if you can't resolve this yourself. Due to the popularity of FM printing, most ink vendors have experience with it and may identify a different series of ink that what you are currently using. There are no set rules about fountain solutions and FM, except to use a good product that is recommended by your ink and plate manufacturer. As a rule of thumb, less is best. Where possible, run the minimum dosage in your fountain solutions that the manufacturer recommends. You might consider getting your fountain solution supplier to come in and check your water performance to ensure it's in spec (conductivity, ph, etc)
Blanket performance plays a significant role when printing FM. In general, FM performs well on good, buffed- or smooth-surface, compressible blankets that are packed to manufacturers’ specifications.
Packing must be stable and uncompressed. Smooth blankets exert less surface tension on ink and release FM's microdots more readily to the sheet. Buffed blankets are most commonly used with FM. They are not as smooth as cast blankets, but buffed blankets perform well on coated paper and on high-quality uncoated paper.

best, gordon p