rocess engineering

How a paint manufacturer's tinting system was completely updated

Guido Strauch*

The main factors which rnust be consid- ered when updating a paintmaker's colour mixing scheme are reviewed, with detailed examples drawn from a recent conversion. Great care was taken to ensure the reliabil- ity of colour formulations and paint quall- ty, and all point-of-sale mixing equipment was either replaced or renovated.

Paint and lacquer manufacturers employ decentralised mixing systems to tint their products for DIY customers and profession- al painters at home improvement and trade Stores. Any company that decides to intro- duce a new paint mixing system needs to make thorough plans in advance to ensure that the move can be carried out smoothly. Next to the modification of existing mixing Systems or the selection of new ones, picking suitable colorimetry software and hardware and adapting existing formula- tions are steps of great importance in this elaborate process. As the conversion pro- ceeds, all these steps must be controlled to ensure that they interface with each other throughout the entire tinting System. A case in point which may sewe to illus- trate the details of this process is the con- version of the paint mixing systems used by the wholesale customers of CD-Color GmbH &Co KG.

Pros and cons of outsourcing

Any enterprise that is about to convert its tinting-paste system will always be con- fronted by the question of which of the

* Contact: Guido Strauch Protec Systempasten Gm6H Wetterstr: 58 D-58313 Herdecke Tel. +49 2330 926-430. Fax. +49 2330 926-,236 pasten@protec.systempasten.de I 1

Figure I: Formulation dwelopment forms the most complex part of the entire conversion process

necessary operations can be handled in- house, and which will have to be out- sourced to the paste supplier, the mixing system supplier, or other third parties. A medium-sized enterprise with a limited number of personnel might find it attractive to procure everything from a Single source by commissioning a contractor to provide any sewices required and to handle the con- version of the mixing system. An enterprise that needs to acquire addi- tional knowhow in the wide field of formula- tion development might decide to send its staff to external training Programmes to ac- quire the knowledge necessary for develop- ing formulations independently. Most cer- tainly, the ability to develop calibration specimens and formulations in-house is ad- vantageous because it enhances a compa- ny's flexibility and independence in the de- velopment of its own formulation database. On the other hand, i f the conversion andlor maintenance of mixing systems are entrusted to extemal sources, the ad-

vantage is that the work will normally get done more quickly than by the company it- self. What is more, any company that spe- cialises in this field will be able to work more cost-effectively in the end.

Correct transfer of data between application software

The first question confronting this compa- ny based in Herdecke, Germany, was whether the formulation software current- ly used was capable of meeting future de- mands. However, after reviewing the alter- natives offered by various vendors, i t was decided to continue using the existing powerful colorimetry software. The paintmaker decided to go on using measuring devices equipped with a gloss trap so that gloss and colour could be meas- ured together and major differences in gloss between the original sample and the prod- uct could be compensated more easily.

rocess engineering I It is important to consider the fact that all the existing formulations must be encod- ed in the database of the mixing system. If the colorimetry and mixing systems use different software packages, data conver- sion cannot always be avoided, and any transfer of data between software pack- ages from different vendors constitutes a potential source of error.

Formulation development needs careful analysis

Developing formulations that use the tint- ing pastes selected in combination with the various base paints is the most complex step in the entire conversion process (See Figure I ) . This step was accorded particular importance because care in the develop- ment of calibration specimens lays the foundations for correct tints later On, help- ing by the Same token to prevent customer complaints about colour nonconbrmity. Before beginning the lengthy formulation process, the company took advantage of the opportunity to examine its own prod- uct portfolio critically. All customers in the paint wholesale trade were analysed indi- vidually and their ti'nting concepts were modified to suit current requirements. Thus, each range of tintable products was purged, new qualities were included, and any 'shelf-warmers' were dispensed with. The first step taken towards the computa- tion of formulations was to define certain framework parameters such as, for exam- ple, release tolerances for the total colour difference AE, which was also to be evalu- ated by visual inspectlon. Contrast ratio and metamerism tolerances were defined at the Same time. Defining the contrast ratio means specify- ing the minimum hiding power require- ments, while metamerism refers tq the ac- ceptability of hue differences under differ- ent types of lighting (daylight or various forms of artificial light). Similarly, maxi- mum quantities were defined for the addi- tion of each tinting paste, while the addi- tion of certain pastes to certain products was precluded or limited. To obtain good hiding qualities from a rea- sonable addition of paste without unnec- essarily and unprofitably overloading a base paint with tinting paste, prefill limits were defined for each base-paint quality in the run-up to the computation of formu- lations. Later On, when formulations had

Figure 2: In a workshop, used mixing systems may be given a general overhaul including repainting

reduce the allowable paste admixtures the colourfans specified by CD-Color, such slightly in some non-premium products so as "NCS Edition 2", and the in-house fan as to optimise the overall material cost of called "Colour Inspiration" were compared the finished product. to the target standard. Whenever noncon-

formities were detected, calibration tints

How to predict two rnillion were reformulated and measured again. To meet the customers' very stringent

formulations reliably colour matching requirements, a major ef-

Formulations were generated in a number of iterative steps. To begin with, calibra- tion specimens were created for a limited number of tinting pastes by analysing dif- ferently concentrated mixes. This involved measuring the influence of various con- centrations of a specific tinting paste on a white - or in some cases transparent - base paint. The resultant reflection or re-emission readings were stored in the colorimetry system as A&S data (absorption cmstant and scatter coefficient) and used to com- Pute the first formulations. NeM, the range of calibration specimens was expanded. by successively adding the remaining tint- ing pastes, with the remaining base paints following last. Each intermediate step was

- fort was mounted to obviate, or at least minimise, complaints about tint devia- tions later On. The rule is that the greater the number of colour specimens that are physically mixed, applied, and inspected, the more precise the eventual formulation master file will be. In the process, a large number of inspection specimens of each quality (at least 150 are recommended) were reproduced to ensure that the formu- lation master file was good enough to avoid customer complaints in the field as far as possible. As a final step, the colorimetry software computed complete colour blocks. A wide variety of tint collections were computed and integrated in the formulation master file. All in all, the new mixing system now

checked thoroughly. During this operation, it was found that THE AUTHOR some pastes were incompatible with the base paints. ~ h i ~ was remedied by modi- Guido Strauch studied business management at

the University of Applied Sciences in Cologne. the tinting and'or the base He hasworked for both Herbertsand laterfor

paint in question, after which the steps DuPont Performance Coatings. Sinc-e 2005, he described above were repeated. has been sewi'ng Protec Systempasten GmbH, In spot checks, tinted paint samples of a subsidiary of Dörken Holding, as key account

been computed, i t was found necessary to newly computed formulations based on manager Europe.