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Estimating Ink Requirements

   

QUANTITY.  Estimating the amount of ink required for a particular job is often difficult.  Allowances for leftovers, spoilage, and wash-ups are hard to predict.

Experience is the best estimating yardstick.  Lacking experience, consult CIC.  Standard estimating charts are available; they give approximate ink coverage figures on various stocks.



FACTORS WHICH AFFECT QUANTITY
.  There are 5 main factors that bear on the quantity of ink needed:

Specific Gravity – Specific gravity is defined as the weight of a given volume of ink compared to the weight of an equal volume of water.  If the specific gravity of a Chrome Yellow ink is 2.40 and the specific gravity of a Diarylide Yellow ink is 1.20, it is apparent that each pound of Diarylide Yellow ink will cover twice as much stock – all other things being equal.

Volume of ink rather than weight is the crucial measure.  The higher the specific gravity, the smaller the volume and the greater the number of pounds needed.

Color Strength – Another factor affecting the quantity needed for a job is the tinctorial strength of the ink.  The weaker the ink, the heavier he film must be to reach a desired color strength.

The tinctorial strength of two inks may be compared by reducing each with the same percentage of white mixing ink and comparing the strength of the resulting tints.  Inks having high tinctorial strength permit printing full-strength color with a relatively thin film.

Surface and Finish of Stock – Rough textured and absorbent surfaces require thick ink films.  Smooth, hard surfaces require minimum film thickness for adequate coverage.

Type of Work To Be Printed – Printing all type mater requires less ink than a solid area of equal size.  Printing an average screen tone also requires less ink than a solid of equal size.

Make Ready – Poor make-ready requires more ink, since an excessive amount of ink must be carried to make up for the deficiency in the make-ready.




INK COVERAGE

For letterpress on coated papers, blacks can be expected to give 150,000 to 200,000 square inches per pound of ink; transparent colors – 125,000 to 175,000 square inches per pound of ink; opaque colors 75,000 to 125,000 square inches per pound of ink.  The offset process usually gives 50% to 100% more coverage than letterpress.  (See sample ink coverage chart).




ORDERING INK

Careful ordering of ink is vital to the production of high quality printing.  Care at the start of a job saves trouble, money, production time and assures the best results.

Ink Suppliers need certain information before the formulator can begin to work.  Each order for ink should be accompanied by the following data:
• Color or colors to be reproduced
• Printing process to be used
• Substrate to be printed (supply sample if possible)
• Processing and/or converting requirements
• End usage requirements
• Cost requirements



COLOR TO BE REPRODUCED

Color memories are short.  Words often fail to describe color and color appearance.  “Red ink,” for example, can range from a bluish red or magenta to a yellowish red that approaches orange, and it can be glassy red or a dull or matte finish.  

Water color swatches and plastic chips from color system books are difficult to match.  Water color swatches often have a milky, flat finish that is difficult to duplicate; plastic chips are coated in such a way that color and appearance characteristics are unnaturally altered.

Printed samples can be good color copy, if the sample is printed on the same type of stock to be commercially used, by the same printing process to be applied, and viewed under the same lighting conditions that the appraiser will use.

CIC’s color guides offer wide ranges of colors.  Use of CIC’s color guide makes color selection easy and saves color matching costs.

When a desired color is not available in the color guide, a “wet sample” (actual ink left over from a previous run) makes excellent color copy.  When two inks can be compared for color side by side, a color match can be quickly achieved.
PRINTING PROCESS TO BE USED.  Printing process, type of press, press speed and method of drying all influence in formulation.  In multi-color or process printing, the sequence of color application also is important.

The facet that a job will be run by letterpress is not sufficient for the formulator.  He must know whether it is a job or platen press, flatbed or rotary.  Each type runs at a particular speed and has a unique distribution system – the factors that influence ink formulation.

On multi-color or process printing, the formulator should know the printing sequence; correct formulation can anticipate problems before they arise.  Wet trapping of successive ink films involves careful formulation.  The first down color should have the greatest tack but must not pick the stock.  Following colors need progressively less tack for proper trapping.

When considerable time may elapse between the printing of first down colors and application of subsequent colors, “crystallization” may occur.  Grease or wax in a first down color can come to the surface as the ink film dries and produce an ink-repellent rather than an ink-receptive surface.  All these are reasons why the formulator needs precise data.



SUBSTRATE TO BE PRINTED

Ink is applied to a variety of substrates or surfaces – paper, carton stock, fibre and corrugated board, tin plate, plastics, glass, rubber, cotton, burlap, nylon, cellophane, and metal foil.

Paper alone comes in a bewildering array of types; glassine, bond, parchment, enamel or coated, super calendered, machine finish, plastic-coated, kraft, and newsprint.  Each has vastly different qualities to which inks must be adjusted.

Bond and glassine are hard-surfaced papers, requiring stiff and tacky inks, which lie on top of the paper and dry by oxidation.

At the other extreme is newsprint, which is so porous that ink penetrates into the paper.  Bond inks cannot be used on newsprint; they pick up the surface and produce fuzzy printing.  On the other hand, newsprint inks would never dry on glassine and bond paper; long after printing the ink would smear to the touch.  These are extremes but the same principles exist with all printing surfaces.



PROCESSING, CONVERTING REQUIREMENTS

Printing is but one phase of processing that a substrate may undergo before reaching the ultimate consumer.  CIC must know what additional converting and/or processing will follow the printing.

The converting process may be strictly a mechanical change in size and shape.  Folding boxes, for example, may be printed, die-cut, scored, folded, glued, and delivered in one continuous operation.  Hence, inks must be formulated to dry to a particularly tough, rub-resistant surface in order to withstand this physical converting in addition to subsequent wear and tear during filling and shipping.

Paper napkins, towels, draperies and the like often are “creped” or embossed with ha design after printing.  Other printed surfaces may be laminated.  Ink formulators must be aware of these converting requirements.

Processing may consist of the application of a protective, adhesive, or reinforcing coating.  Bread wrappers and milk containers often are waxed after printing to make the paper moisture-resistant.  Beer or food containers may undergo sterilization or pasteurization.  CIC must know these processing requirements in order to formulate, for example, bread wrapper inks with pigments and vehicles that will not bleed in hot wax, or supply metal decorating inks that will not change colors when subjected to high temperatures during processing.



END-USE REQUIREMENTS


Inks for soap carton printing require careful selection of pigments and vehicles to prevent bleeding or discoloration by the caustic action of the soap.  Bags and boxes for food packaging require inks free of objectionable odors.  Lamination requires light fastness and bleed resistance in ink pigments and vehicles.  The ink supplier must know the end-use requirements of the job.


COST REQUIREMENT


The most economical ink for a job is always the ink that performs satisfactorily.  Cost per pound is a secondary criterion.  

When alkali-resistance or special light fastness or other special properties are required, ink suppliers must no doubt use more costly pigments and other ingredients in the formulation.  Economy in these cases is often possible only at the expense of quality.



HANDLING INK

PACKAGING.  When ordering ink, specify how it should be packaged for ease of handling not only in shipment, but also in the shop.  Gravure inks, for instance, are fluid by nature and are generally used in quantity on long runs; hence, they are delivered in 30 or 55 gallon drums.  News ink is shipped to large customers by tank or truck or railroad tank car and pumped into tanks for storage.  Most suppliers ship ink in cans, kits, or drums of different sizes according to instructions.

DELIVERY.  Be sure to include a delivery date when ordering ink.  Idle presses mean lost money.  Remember that ink formulating is a prescription business and suppliers need time to do their work well.  

STORAGE.  Inks should be stored where they are not subject to excesses of heat or cold.  They should be carefully stored and classified according to kind of ink, color, and date of delivery.  This makes it simpler to tell how much of a given type of ink is on hand.

Lithographic Ink Coverage Chart – Sheet Fed

Grade of Stock Enamel Litho Coated Dull Coated Machine Finished Antique
           
Black 425 380 375 400 275
Rubberbase Black 445 430 425 435 335
Purple 360 350 320 350 235
Process & Transparent Blue 355 340 335 340 220
Transparent Green 360 350 335 350 235
Process & Transparent Yellow 355 355 340 340 220
Chrome & Lemon Yellow 285 260 250 250 150
Persian Orange 345 325 310 325 225
Process & Transparent Red 350 345 340 340 225
Semi-Transparent Red 350 340 325 340 175
Brown 345 335 325 335 225
Silver 335 300 285 295 220
Gold 125 115 115 115 75
Opaque White 200 175 165 175 135
Tint Base 400 380 375 385 25
Fluorescent 135 120 120 120 85
Over Print Varnish 450 425 415 425 X
           


The above figures represent, approximately, the number of thousand square inches that a pound of offset ink will cover.  As the carefulness of the pressman in making ready and in setting the fountain has a bearing on the amount of ink required on the job, and as the affinity for ink varies with different paper stocks even in the same classification, it is evident that the above chart cannot be guaranteed as absolutely correct.
     
 
 
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