? I’ve been told we can calculate the spectrophotometric values of our print even through we only have a densitometer.
Is this correct?
The answer is no. But, as usual, that is the short answer. The long answer is also no, but I think some explanation would be useful.
So what do densitometers do? In essence, they measure CMYK process colour ink film thickness using preset colour filters, not the colorimetric values of the CMYK inks. On the other hand, a spectro-photometer measures the colorimetric value of any colour, including CMYK using CIE LAB values and other colour measuring metrics.

The point behind the question is possibly based on the fact that the ISO 12647-2 2004 Amendment 2007 standard printing conditions are based on colorimetric values, which accurately describe colour – CIE LAB numbers rather than CMYK process colour densities.

So why is this, and why is it important? Density measurements, as stated, measure ink film thickness using preset colour filters but are blind to the actual colour, so if the CMYK colours are not accurate to the standard, ink density will not pick this up.

So only by using a spectrophotometer and referencing the ISO 12647-2 CIE LAB values for the relevant printing condition can the CMYK colours be accurately judged.

One can see that if the colour of the CMYK process inks is not correct, colour accuracy, even at a ‘correct’ density, will not match expectations or the verified contract proof.

Going back to the question, spectrophotometers are more expensive than densitometers, so one can see the issues. However, if the presses used have not got closed-loop controls, they do not need to have an expensive spectrophotometer on every press.

Using one spectrophotometer to check CMYK CIE LAB values, these colorimetric correct values can then be measured with a densitometer for day-to-day use on press.

To sum up, densitometers cannot measure colour, just ink film thickness. If adherence to ISO 12647-2 is needed, at least one spectrophotometer is needed to measure CIE LAB values for CMYK process colour to meet the ISO figures.

Paul Sherfield







? One of our customers is complaining his job smells. What could cause this, how could I
explain this to the client and how could it
be avoided?
I’ll base my suggested solution on previous observations. Out of the three most common printing processes – offset, screen and flexo – I will assume that the odour issue has occurred within the conventional offset ink application on paper or board.

Within the offset process, ink dries through the oxidisation of evaporating materials contained within the ink and the absorption of resins/binders into the paper to provide rub resistance. Many of these types of jobs are also varnished with a neutral finish protection or enhanced gloss, silk or matt finish.

The main consideration when trying to locate the origin of higher than expected odour is storage versus final drying time. Often a commercial print job is produced with a tight deadline, which might cause the finishing and converting to be undertaken before the inks and varnishes are finally dried through. This is made possible by the fact that most conventional inks have an initial short setting time that allows runs such as leaflets or brochures to be handled and finished within a reasonable timeframe.

In some cases, the job in question is then prepared for dispatch shortly after printing. If the job is then shrink-wrapped and packed in boxes or on a pallet, this could lead to one of the main reasons for a printed job being considered ‘smelly’ by the end user.

Evaporating material in the inks and varnish becomes trapped and basically the job can’t ‘breathe’. Therefore, when the packaging is removed, the customer experiences a high surplus odour. This happens if a job is packaged before it is completely dry even though it is safe to handle.

It is very rare that one printed sample smells in isolation once it has been fully aired. Odour intensity varies according to the film weight of the ink and varnish, which means that higher film weight jobs are more likely to have increased odour.
Sun Chemical has a specific range of conventional products for low-odour work called Irocart GN. These inks are available in process and Pantone shades and are usually used for food packaging requirements.

Kevin Purdy







? I usually try to be quite generous with our employee remuneration, but it’s been a tough year for us and I’m trying to decide what’s appropriate for end-of-year bonuses and salaries in general going into next year. Do you know any good formulas to help me crunch those numbers?
Whether the financial climate is tough or not is immaterial. Every business needs to constantly monitor and seek to improve its level of performance. He who stands still will ultimately move backwards. Therefore, my general way of thinking is not to give pay rises or bonuses across the board, just for the sake of it. I’m a great believer in building in exceptional rewards for overachievers and those individuals that really do go the extra mile.

It is important to set out realistic goals prior to the start of the financial year. Decide on your targets and what KPIs need to be achieved on a quarterly basis, and then put in place two forms of bonuses: those for achieving goals; and those for overachieving. Make it clear to your staff what is expected of them and what can be achieved financially for putting in that extra performance. It is my belief that all team members need to feel that their earnings potential is not limited. When it comes to salary increases, employees know their goals and as such should understand their potential to increase earnings. In this situation, they should naturally pull in the right direction, rather than ask for a pay rise. If an employee merits a salary increase in recognition of exceptional performance, then so be it.

Neil Edwards