Preparing samples for an ink database

InkMaster Sample Preparation Guide


Why do I have to prepare an ink database?

The computer, like the colorist, is only as good as the information with which it is provided. The computer needs to be educated about the inks and substrates that you use, just as you were when you first began to do color formulation work. The spectrophotometer and computer work together to develop color matches, just as the colorist's eyes and brain work together to formulate colors.

How precise do I need to be in preparing the dataset?

The computer needs to know how your inks will perform in a formula. To best determine this, each ink must be entered at various levels. The computer will expect that your input is completely accurate, therefore, you must prepare your dataset with precision and accuracy.

What will I gain by careful preparation of the dataset?

By following the instructions within this sample preparation guide and adapting the recommendations to your process, you should generate an accurate, predictable dataset. The result of which will save you time and money by making you a more efficient colorist. Time spent now will pay off in the future.

Important Considerations

When creating a dataset, the most important considerations are that this data is repeatable and accurate. You should work to eliminate as many variables as possible. Repeatability and accuracy needs to be accomplished at the laboratory level and emulate production. Any loss of accuracy will be magnified when the computer predicts color matches. Remember "garbage in" usually results in "garbage out".

Thus, as the colorist is responsible for the dataset, you need to make some decisions about techniques and equipment in the creation of these ink displays. The accuracy of the dataset in predicting formulations for your production process relies upon the proper choices for inks, substrates, sample preparation tools, and techniques.

Recommendations for creating a proper database

Substrates:

The substrate you use for the creation of your dataset should be similar to what you use most for production. Once a substrate has been selected, make sure you obtain enough to make the whole dataset, as switching substrates can introduce error.

Typically, two to three calibration sets are required for each of your ink systems. One for coated paper, one for uncoated paper, and one for film if required. The best choice would be white paper stock (with no optical brighteners). Good paper stock, specifically designed for calibrations, can be purchased from suppliers identified in Appendix A. Colored papers, such as kraft, can usually be accommodated at the time of formulation without a specific calibration set. If you only formulate on stocks like kraft or foil, you can get a slight improvement in initial match accuracy by creating an additional calibration set for that substrate. If you use mylar film or foil, it should be thick enough to allow ease of use. Thin films can be difficult to print on due to wrinkling.

If mylar substrate is used, the mylar should be tested for its Dyne levels. Test kits are available for this purpose (see Appendix A).

Inks:

Select single lots of all the inks that will be present in the dataset. Make sure you have enough in the case that it becomes necessary to remake any part of the dataset. Store these samples and do not use them for any other type of sampling or lab work.

When entering your inks into the dataset, you will need to tell the soft- ware the composition of that ink (concentrate, extender, solvent, and specific gravity). By properly entering this information, you will be able to accurately formulate and track the amount of Concentrate (pigment load), Heavy Ink (concentrate + extender), and Light Ink (heavy ink + solvent) you use. Remember: Light Ink is "press ready" ink. Ink-Master expects all formulas in terms of Light Ink.

If you use a coating or overprint varnish in your production, then you should also use it on all of your samples. A good dataset will mimic your production process.

Sample Size:

The sample weight should be large enough as to improve accuracy by reducing the effect of weighing errors. As a low limit, use 1000 times the minimum readable amount on your balance. Therefore, the minimum batch size for a balance with 0.01g readability is 10.00g.

What lab equipment do I need to create an ink dataset?

Balance: Used for precise weighing of your ink samples. It should be electronic and accurate to two decimal places for accuracy in weighing.

Mixing: As with all processes, you want to duplicate the mixing process that is used in you production. If mixing is done manually, the same person should be used for all samples within a dataset.

Proofing: A reliable proofer must be used to insure the uniformity of samples. Manually operated devices can lead to variation between samples. A good proofer can repeatedly apply an even ink film through constant pressure and print speed.

Ink Pipette: A volumetric measurement of the ink used to create a proof. A variation in the amount of ink used will obviously change the thickness of the ink film.

Viscosity Cup: Used to measure the viscosity (how fluid it is) of your Light Ink (press ready). Any variance in viscosity will result in a variance of ink film thickness and will effect color.

See Appendix A for a list of suppliers of this equipment.

How do I choose which type of database type to use?

Your Ink-Master software can formulate using two different methods, Single Constant and Multi-Flux. A Multi-Flux dataset is used if you add opaque white or you have high scattering inks. A Single Constant dataset is used for transparent inks.

Special Considerations for a Multi-Flux dataset

A Multi-Flux dataset is used for scattering inks and inks to which opaque white may be added. To properly characterize these inks, it is necessary that the inks be measured over white and over black. Various substrates can be obtained with the black stripe included. Suppliers of these substrates can be found in Appendix A. Kraft paper should not be used to create a Multi-Flux dataset. Instead, you should use an uncoated white substrate, and then measure the kraft as the substrate for your match.

What concentration levels should I use to create my dataset?

When creating a dataset, the software needs to "see" your inks at various concentration levels. We recommended you create 6 different concentration levels for each ink. Our recommended ink concentration levels are listed for you in Appendix B. Please record the specific gravity (density) for your 100% level. If you do not know the value, you can simply take an ink pipette, measure five nics (1 mm3 ), and weigh that amount on an electronic scale. The value that you get will be the specific gravity (density) of that ink in grams/milliliter.

What other samples do I need to create?

You will also need to make cross-mixes. A cross-mix is a sample that contains 3-5 different inks at known percentages. These samples are used to test the accuracy of your dataset. A properly prepared dataset will be able to correctly predict the known formula of these cross-mix samples. See Appendix B for some examples of cross-mixes.

Creating your samples.

To begin creating your samples, you will need to have all necessary equipment ready, a supply of substrate, and your inks. After selecting the proper concentration levels and selecting the sample size, you can begin weighing your samples. You should be very careful in recording the actual weights of your samples. The software will accept any value, but that value must be accurate. For example, if you are creating a 10% ink level, but you overshoot and weigh 10.08%, you can use this level, just enter 10.08% into the software.

Next, use your standard procedure for mixing, measuring, and proofing your ink, making sure that you use the exact same procedure for every letdown.

The first sample you should make should be the lowest level of your black. This sample should be created twice, repeating the entire process exactly. These samples should then be measured and compared to one another. The purpose of this is to check the repeatability of your process. The larger the difference between these two samples, the more variance exists in your process. You may need to refine your process to minimize this variance.

It is important that you operate in an environment controlled as much as possible. Any changes in temperature or humidity will effect both your inks and substrates. You should also ensure that you keep your ink mixtures covered, as any evaporation of solvent will change the overall make-up of you sample.

Your first dataset should be small (3-5 inks) so that it can be evaluated when you attend a formulation class. This will minimize the number of samples that need to be remade, should there be any necessary changes.

X-Rite Ink Formulation Class

The X-Rite class you attend will teach you the proper use of the instrument and software that you have purchased. During this training you will receive instruction on how to make the most of your powerful new tools.

To maximize this learning experience we ask that you do some preparation and bring the following materials:

• A dataset of 3-5 inks

• Cross-mixes that use the inks in your dataset


 

Appendix A


Equipment Suppliers:

Substrates

The Leneta Company
15 Whitney Road
Mahwah, NJ 07430
(201) 847-9300

Proofers

IGT Reprotest
1450 E American Lane
Suite 1400
Schaumburg, IL 60173-4973
(847) 330-6322

Viscosity Cups

Norcross Corporation
255 Newtonville Ave
Newton, MA 02158-1898
(617) 969-7020

Dyne Level Testing (for mylar)

Sherman Supplies
(612) 430-9504

Misc. Lab Equipment (balances, etc.)

VWR Scientific
(800) 932-5000


Paul N. Gardner Company, Inc.
Gardner Building
316 N.E. First Street
Pompano Beach, FL 33060
(954) 946-9454


 

Appendix B

Recommended Ink Concentration Levels


100.00% Ink
75.00% Ink
50.00% Ink
25.00% Ink
12.50% Ink
6.25% Ink
3.13% Ink


Cross-Mix Example

Below is an example of a 5 ink dataset and the cross-mixes that would be necessary to test the dataset.

Cross Mix #1 (Orange)
Yellow 70%
Red 25%
Green 5%

Cross-Mix #2 (Lt. Blue)
Extender 70%
Red 5%
Blue 25%

Cross-Mix #3 (Aqua)
Extender 5%
Blue 70%
Green 25%

Cross Mix #4 (Red)
Red 85%
Yellow 5%
Extender 10%

Cross Mix #5 (Green)
Yellow 25%
Green 70%

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