This document covers the best practises needed to ensure that all parties involved in paper trials, end customers, printers and paper merchants and mills can achieve the optimum results on the chosen stock.
It is aimed at the web offset publishing markets, however it can be used for other print markets and printing methods.
As well as promoting best practise for these paper trials it will also provide a method and scope to manage expectations when they are not followed.
Current Practise
The normal procedure, at present, when a new paper is trialled for a customer, is for the paper company to supply a trial reel of the chosen paper.
This reel is then used at the end of the customers print run, in order to compare with the current paper used for that publication.
This practise will only provide a good comparison if the trial paper is similar in printing properties to the paper with which it being compared i.e. a similar Light Weight Coated stock. Even then the ink densities may need adjustment which may result in the dot gain changing, creating a need for new plates to be made to reflect this change.
If the trial paper is very different from the current paper used, say a matt coated, super calendared or uncoated, then the trial run will not show the optimum colour reproduction on the paper. In this case no judgement on colour issue should be made from this trial.
The only areas that can be judged are the overall look and feel of the trial stock and its performance on press.
Best Practise procedures
When, as described above, the trial paper is different in printing characteristics and colour reproduction is to be part of the evaluation the following will be needed:
- Establish the correct ICC profile for the paper to be used together with the dot gain curves needed.
- Repurpose the page PDF’s used for the main press run to this new ICC profile. This can be done by using a colour server that the client, prepress house or printer may have, or by using the original Adobe InDesign CC or QuarkXPress files and repurposing to the new paper and CMYK ICC profile.
- Consider if new contract proofs from these repurposed PDFs using the new ICC profile would be useful, even if proofs were not supplied for the original publication.
- Remake printing plates with the correct dot gain compensation curves from the repurposed PDFs for the paper trial. Check with the printer to see if they run the trial paper on other work. If so, they may have dot gain compensation curves for the trial stock.
- Set the press automated ink controls to the new CIE Lab CMYK figures that the new ICC profile may require.
- When at optimum ink weighs to match the CMYK CIE Lab values check that the dot gain meets the ICC profiles/printing standard specifications.
- Then run the trial paper at normal press speeds.
Only by carrying out the above best practise procedures can the trial paper be judged for colour reproduction. This will be needed when the trial paper differs in type from the paper used to the current production run.
However, there are, of course, financial implications. Extra plates and press time. All involved need to measure their expectations and requirements against the extra costs of following best practise in for these paper trials.
All parties involved must agree the scope for the trial. If it is to judge the colour reproduction of the test paper, the these ‘Best Practise’ procedures should be followed in order to judge and compare the substrates colour reproduction accurately and fairly.
As part of this process, it is ideal if representatives from the client, paper manufacturer/merchant attend the press paper trial. If this is not possible a reporting procedure should be agreed with the printing company carrying out the trail. Press sheet or folded section of the paper trail should be sent to all involved with printed samples on the current stock.
Stora Enso gives information of the correct ICC profile to use on the Technical Data Sheets for each paper. They also have a range of specially produced ICC profiles for some of their papers which will provide optimum results.
https://info.storaenso.com/technical-resource-centre
Stora Enso Technical Sales-Europe
The Missing Horse Consultancy Ltd 02/2021
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