Presstek 34DI Solid coverage

[lregan]

We are having issues with uncoated stock on our Presstek 34DI. We experience unacceptable solid coverage and blown highlights.. We are using Via 100# text and cover. Generally 100% recycled. Is this a normal experience? Is it a press issue or should there be a prepress adjustment?
Thank you

 

[Ret Heidelberg Instructor]

Ret Heidelberg Intructor

Ret Heidelberg Intructor

I don't know the Presstek DI but I am familiar with the all of the Heidelberg DIs. You might need to use another curve from pre-press for uncoated papers. This would involve running a calibration for dot gain for coated papers to densitrometric values for coated and then repeat the test for uncoated paper.
You might also need to examine how your solid colors are built up from prepress. For example if you print a solid black using a 100% black only you might get away with an acceptable result. However if you use a 60% screen of cyan under an 80-100% black you will get what we used to refer to as a rich black. In some cases we used a black made up of 40% yelo 40%cyan 40% magenta and 80 % black. This really hepled with the hickey siuation also.
I f you are using this protocol already then I apologize for telling someone how to do their job. I am only relating this to you because in my experience in numerous situations I found that customer files did not always come over ready for CMYK output.
I also suggest that you get Presstek involved also. I re-call many a situation where I was called in to address a press problem that was a pre-press problem. At least I was able to get a pre-press tech from Heidelberg to come in and assist with the problem and we would work together. Hope this helps. keep us posted for curiousity sake.

 

[bhm8hwcm]

We run a 34Di so hopefully can be of some help.

Blown highlights - I would start with looking at the images first to see what they look like. If images are ok then something is going wrong most likely at the rip. It is most likely a curve issue and so like Ret Heidelberg Intructor said above you may need to redo your calibrations for uncoated stocks reading dot gains etc. At the rip level you can check your separations to see what % dot is being rendered for your plates. Rip the file, click on the plate to view separations, then click on the percentage icon and with your mouse select a small area and it will tell you what the percentage is for each colour. This may help in trying to see what is going on. You could also add a tone curve to your page setup for uncoated 'bumping' up some of the highlight areas but this may take a little fiddling around and you need to be careful when dealing with highlights as a % here or there can create color casts I find. Best and safest option is to do complete recalibration...I just did this about 2 weeks ago but new curves still need tweaking.

I agree with Ret Heidelberg Intructor regarding creating boosts as well to help with solids. For black many times we use a photoshop black (go to photoshop and select black and see what you get). By running less than 100% K we get less hickies and the other colours help make the black dense.

One last thing re the solids is your blanket squeeze. When running uncoated we have to squeeze much more than when running coating stocks. If your laydown is blotchy then this may very well be the issue. Don't run much Via but I think it is a decent stock and should print better than run of the mill uncoated stocks.

 

[Disappointed]

Yes, sounds like a recalibration is in order. We have run a 34 but now have a 52di but the process is the same.

For maximum accuracy, when scanning the cal test patches, do not scan them on the PDSE unit but read them one patch at a time, the difference is amazing. We have improved further by using a calibrated Gretag spectrophotometer instead of the press unit, this is better still, especially at the extreme ends of the tint ranges.

We recalibrate every couple of months.

Set the roller pressures FIRST and fit new blankets if needed before calibrating.

 

[Ret Heidelberg Instructor]

Ret Heidelberg Instructor

Ret Heidelberg Instructor

Good post by Disappointed. I totally agree with the rollers being checked and set. I would like to add that when I used to calibtrate this type of press for Heidelberg we also used new blankets. However I found out later on when I did some color management involving other presses, it was recommended that the blankets should be run in first so as to try and replicate plant operating conditions. That's my 2 cents worth.

 

[Disappointed]

Yes, all the above plus,

Calibrate at your usual running speed. I.e. Don't calibrate at 6000 and run at 8500, the difference is noticeable but not severe.

Dave

 

[Skidmark]

Put a fresh set of Syn-Tac rollers in it and never look back!