measurement of colour in reflectance · • one of the main advantages of benchtop instrumentation...

CONFIDENTIAL

Measurement of

Colour in Reflectance

Practical Examples of

Formulation Workflows

Richard Gray – X-Rite

Medical

Dental

Photo

Industrial

Laboratory

Graphic Arts

Retail Paint Munsell

Pantone

Identify This Colour

Identify This Colour

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Which Colour Is It?

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Which Colour Is It?

Simultaneous Contrast

Simultaneous Contrast

Simultaneous Contrast

Simultaneous Contrast

Afterimages

Afterimages

6 2

Colour Deficiency

Colour Discrimination Tests

Farnsworth-Munsell 100 Hue Test

Inter-Society Color Council Color Matching Aptitude Test

HVC Color Vision Skill Test

Japanese Color Aptitude Test

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• 1. Repeatable method of proofing:

• A consistent and homogenous coating layer is essential for any formulation

system to function correctly.

• Sample proofing also has to be independent of operator.

• Typically a maximum variation of 0.25 DE within a sample

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• 2. Consistent Substrate for Translucent Samples:

• Leneta cards are ideal as they provide a consistent black background for

opacity checks. Alternatively, specific customer substrates or Q panels can be

used if required.

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• 3. Accurate Viscosity Measurement (If Applicable)

• Certain Formulation systems will allow for dilution factors in liquid systems

• System will report on a formulation and % of diluent required

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• 4. Instrumentation Type

• Typically Industrial style formulation will use sphere geometry – this gives the benefit of

formulating with (Specular Included) or without (Specular Excluded) the effect of surface

gloss.

• Will also allow measurement of highly reflective / mirror finish samples.

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• 4. Instrumentation Type

• However it is also possible to measure a range of samples directly in paste or liquid form

using non-contact spectrophotometry:

• This allows for the accurate capture of irregularly shaped or curved samples.

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• 5. UV Calibration

• One of the main advantages of benchtop instrumentation is the ability to control the UV

content of the light source.

• By calibrating this monthly you can ensure consistency of all production results. Essential if

you are using samples containing optical brightening agents.

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• 6. Preparation of Calibration Sets

• The key to any accurate formulation system is the diagnostics of the colourant file. There

are numerous ways to construct the file initially:

• Reflectance (opaque)

• Reflectance (transparent)

• Reflectance (translucent)

• Reflectance / Transmittance

• Modern formulation systems also give the advantage of allowing multiple resins (at

differing opacities) to be loaded within the one colourant file.

• Different coloured layers can also be loaded into the software as substrates to allow multi-

layer formulation build-up.

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• 7. Definition of Standard

• Measurement of a standard at the instrument will capture the exact measurement status

automatically.

• There are also several other ways to define a target colour without the need for a physical

sample to measure:

• Digital Libraries (Pantone, RAL, NCS, etc.)

• CxF (Colour eXchange Format)

• Munsell

• Reflectance Data in Tabulated Format

• Specific L*a*b* or L*C*h* coordinates

• Data in pre-defined job format

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• 8. Formulation Options

• Setting up a colourant file using the contrast ratio method will allow for a great deal of

flexibility within your specific workflow:

• Define minimum/maximum opacities/loading levels

• Allow database searches to a closest previous match

• Auto correct to an existing recipe

• Allow formulation at multiple coat weights

• Allow output by weight or volume and specification of

formula units

• Connect directly to a dispensing system with remote output

functionality

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• 9. Formulation Selection

• Selection Criteria can be tailored to whatever is important to the final user requirements :

• Closest DE

• Least Metameric

• Lowest Cost

• Specific Opacity

• Closest Curve Fit

• Specific Illuminant

• Optimum Score function will allow a

combination of factors to be expressed

as an overall integer.

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• 10. Correction Workflow

• Corrections can be specific to production or laboratory workflows:

• Correct to a specific opacity

• Allow alternative colourants

• Correct to specific production amount

• Correct at Alterntive Thickness

• Use Performance Factors

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• 11. Further Options

• Within the Workflow specific batches can be defined as wastes for easy work off of

redundant stock:

• Formulate to a range of ‘Waste’ pigments

• Select matchings with maximum % of waste by

• specifying zero cost amount and searching on cost

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• 12. Net Profiler

• When formulating to digital standards the performance of your instrument in a supply chain

is essential.

• Net Profiler allows the user to verify and correct instrument variations at the customer site.

• Measurement of a calibrated tile set or Munsell chart

• Comparison of data on-line to reference master standards

• Correction for instrument drift without need for recertification

• or repair

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• 12. Net Profiler

• Net Profiler allows for larger supply chains to monitor and check instrument performance

• remotely

• Certificate of Performance available online or locally

• Instrument can be profiled the recommended 1 month period or more frequently

• NIST traceable calibration certificate issued to tie in with ISO certification

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• 13. And Finally....

• Visual Assessment is still the final approval point in a number of workflows.

• What is wrong with this method of visual assessment ?

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• 13. And Finally....

Select the correct light source(s).

Viewing booth should be kept clear of extra samples.

Samples should be placed inside the light booth.

Orient Standard and Sample in same direction, side by side, touching.

Depending upon gloss of the samples, determine a standard viewing geometry.

Limit the amount of ambient light flooding the viewing booth.

If assessor is wearing brightly coloured clothing, a neutral lab coat should be worn during assessment.

If assessor wears glasses with tinted lenses, they should be removed for the assessment.

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• Questions will now be taken – Thank you for your attention !

Technical Support:

EMEATechSupport@xrite.com

00800 700 300 01

www.xrite.com www.colorservices.xrite.com