Hi Guys

Im new at 4 colour litho process work. Ive got a calibrated densitometer. what density and dot gain values should i be looking at. also should i be zero-ing the paper on every pull for murray-davis or should i add the paper density to the equation. Also what print sequence should i be using. the last few jobs i did was ycmk, not sure that this is right.

please help.

Sequence depends on ink tack. I have always run KCMY, black being down first, and haven't had any problems. As for densities: K - 1.90, C - 1.30, M - 1.30, Y-.90. Now those are just starting points. Adjust as necessary for your inks, paper and press. Ink densities on offset paper will be higher than on gloss paper.

Thanks Xallux. I'll give that sequence a try. About the density measurements, do you zero the paper for the pull or does that measurements include paper.

I usually zero out for each job, just so my starting point is the same. Let me know how everything works out.

Hi,

All the people i know use the same Density values. C=1.40 M=1.40 Y=1.30 K=1.80. These are the values i use when i'm printing glossy paper. If i'm printing uncoated paper the following values work fine. C=1.15 M=1.15 Y=1.00 K=1.50.
The values offcourse depend on sort of paper and photo quality. I also always calibrate my D meter before every job.

With love from Belgium

The previous postings are all in the ballpark - ultimately you're selling the job not the control strip. ie if the job looks like the proof the densities are pretty much irrelevant.

However, print sequence, particularly on coated stock is crucial. KMCY is the way to go for the majority of work, especially if there are colour values that are close to reflex blue (80m/100c). You can switch to KCMY if you have colours values like (100m/50c). This improves the 'lift' or 'trap' between those inks.

You don't mention how many units your press has tho' - this can change the above advice regarding sequence considerably.

You should indeed not only look at the colourstrip. That's what they teach you at school.
The colour sequence we use is KCMY on a 4-colour ryobi press. We also have an eight colour Roland 500. But we also use the KCMY colour sequence there. I sometimes change the sequence if it's a difficult job.

With love from Belgium.

With regards to zeroing the densitometer, always zero the paper as the different "whiteness" between different stocks will have an effect on the result.
Murray Davies is a conversion factor, also called an n factor or yule nielsen factor. Murray Davies is a factor of 1, meaning if you multiply a figure by it you will get the same result. and is used to calibrate a substrate, it is usually only used on plates, because of the number of different papers out there it would take too long to find the yule nielsen factor of all of them, which is why we use murray davies. This has little or no effect when measuring density and is only really needed with dot gain