As an object lesson in accessorizing, consider the prolific TV auto-insurer who’s TV ad finds Flo consoling a rookie seller who had just failed to persuade a prospect to select their brand of security. The parody ends with Flo offering an ice-cream treat as the consolation prize but when pressed by the boy for “and sprinkles on top?” She flatly refuses. “Sprinkles are for winners”.
Sprinkles are very much like accessories. Accessories in the manufacturing arena, which may be seen as an afterthought, possibly even an extravagance, are likely the best way to ensure the manufacturing process. It is to this end that accessories, like sprinkles, are for winners.
Before you consider which criteria will help you determine which types of shop accessories and how much of it you should invest in, consider whether you’re a top-liner or bottom-liner. Top-liners prioritize the customer and quality of the product and lean toward investments which lead to revenue enhancement—improved quality, consistency, on-time deliveries, and enhanced profit opportunities. Bottom-liners prioritize savings, such as increased throughput, raw material savings, reductions in scrap, and those investments which help contain costs.
Neither is right nor wrong but both are “faith-based”, diametric opposites and therefore should never be challenged. Revenue enhancers, or top-liners, feel cost containers, or bottom-liners, lack of concern for the customer and have little respect for sales, marketing, or the value proposition itself. On the other hand, cost containers think their counterparts are blue sky dreamers and don’t respect the fact that a penny dropped to the bottom line is a full penny saved. They drive the bus of cost control and money savings.
If you are a bottom-line type, ask your vendor for a value proposition which focuses on cost containment. If you prefer top-lines, ask for a value proposition which focuses on revenue enhancement. Once you assemble the relevant criteria, consider which accessories take priority in terms of your needs and budgetary constraints. In a sentence, we need to decide “What do we buy next and how soon?”
Calibration and monitoring
Let’s divide “testing” into two separate elements: calibration and monitoring. Calibration takes a lot of well-invested time, and usually uses an expensive, digital meter which may require training on usage and interpretation of the results. Calibration should be done in order to set a baseline for monitoring. Monitoring is fast, free or affordable, and anyone who can understand “go; no-go” can monitor.
Calibration and monitoring throughout the screen printing process is absolutely necessary for best results. Luckily, there are a variety of calibration and monitoring tools and techniques that appeal to both top-liners and bottom-liners. What’s more, these techniques help ensure profits and justify the time and cost of equipment.
Tools of the trade
Stencil evaluation: Mesh and/or screen suppliers can offer assistance in quantifying the screen parameters. It may be a visit with instrumentation or a few screens can be shipped out to them for quantification. Then, by using an exposure calculator (a very low cost tool), a gray scale, a resolution scale, thermometer, timer, and hygrometer, we can monitor screen-to-screen results to see if they are consistent. Finally, calibrate, quantify, and then monitor EOM, RzS1, RzS2, lamp output, and moisture content.
Elasticity: Elongation is a one directional measurement, and 100 percent elasticity is a measure of complete recovery after a given amount of elongation. There are very sophisticated meters and devices available, but for the cost containers who worry about product failure in the field and subsequent returns, there is a low budget solution for most needs.
Find a retensionable roller frame and build a file or film with six solid ink rulers—positioned right, center, and left edges, top, middle, and bottom edges. Print this image on your material and cure it as recommended. Get the percentage of elongation per color and film thickness from your supplier. Then load the cured rulers into the roller frame, tension, measure the elongation, and the time for complete recovery. If the ink is as elastic as the fabric, the elongation will transfer evenly from the edges to the center. If the tensile strength of the ink film is higher than the garment, the elongation at the edges will be greater than the center. If the ink film cracks before the garment degrades, we may need a more complete cure, a thicker ink film or a different ink.
Wet and dry crock: There are published standards on crock testing per color. Wet crock is a measure of the resistance of the ink film to lose color when laundered or exposed to perspiration. Dry crock is a measure of resistance to lose color when abraded. Water-based inks are not particularly good film formers and as such are very susceptible to crocking issues. With a few squares of linen, some white vinegar to simulate perspiration, and an overview of the procedures one can easily establish crock testing for almost no expense.
Cured ink-film integrity: Applicable with a solid area of plastisol ink, cured ink-film integrity can be gauged with a pencil hardness test. A low cost holder keeps constant pressure on any one of a variety of sharpened pencil leads. The lead is dragged across the surface of the printed area under consistent pressure and is then inspected under magnification; 10X is acceptable, but 40X is excellent. For the hyper-budget minded, a slightly softer pencil can be held by hand and struck against a straight edge. In house standards can be easily established to gauge the durability of the ink film.
Dryer performance: This can be quantified with non-contact IR pyrometers (both dryer and flash), analog donut probes, anemometers and temperature-tapes. Bear in mind these are not assurance of ink durability, only dryer performance.
Plastisol is less susceptible but with water-based colors or discharge, moisture content in the oven which was removed from the garments is an impediment to cure. Monitor elasticity, wet and dry crock resistance, and ink film integrity with pencil and solvent evaluations to interpret the longevity of the printed image.
Ink opacity cards: These are coated, heavy-weight papers onto which we can screen print or use a draw-down gauge to drag white or colored ink across the card, the top half of which is white and the bottom half is black. This allows us to compare the top to the bottom. A densitometer or colorimeter can be used to quantify the results which are relevant for an incoming material QC test. Be forewarned; opacity on a card is not at all a predictor of opacity on a low fabric, knitted garment.
Ink gloss and smoothness: For the frugal purchaser, print a large donut of white ink on the stock side of Quilon coated, heat-transfer paper and cure the ink. Then peel the ink from the sheet and lay it on top of your direct white print to compare several attributes. The gloss and smoothness of the ink from the transfer paper will be much higher but a gloss meter can sensibly grade the direct print for aesthetic consistency. Make sure to gauge the printed image at the center of the screen, which will be rougher and lower gloss, as well as at the edges which will have a smoother and glossier finish. Increase the thickness of a single pass of color and its gloss and smoothness are likely to decrease. Print on top or a flashed underbase and the gloss and smoothness are likely to increase.
Blade durometer: These types of gauges are not very expensive as gauges go but what we want out of a blade is a metric on its flex, fade, fatigue, and failure. Failure can best be estimated if we watch the residue on the non-image areas of the screen and compare the beginning to the end of the stroke 1) with a new blade and 2) with a suspect blade. If the suspect leaves more ink at the end of the stroke then it has failed and may need to be replaced. Meanwhile, durometer is a silly measurement. Flex can be gauged by taking two blades and putting them edge-to-edge with the blade lengths overhanging a table 6" to 12" and see which flexes more or less.
Solvent test for fusion: Cellosolve acetate for relatively thin plastisol films and ethyl acetate for thicker plastisol films are used to quantify the degree of fusion. These tests are simple but must be calibrated per the brand of ink and per color to be meaningful. Generically, a red pencil eraser is used from the inside of a printed garment where the ink got the least heat. Several drops of the solvent are applied to the print and the eraser pushes the print and garment on a white offset paper laid on a hard, non-absorbent surface for nominally two minutes. If the ink transfers to the paper, the level of sure is incomplete.
Ink matte-down vs. fibrillation: Fiber matte-down is formulated into the rheological profile of the ink but fiber matte-down is best at the maximum stroke speed. Matte-down is best on a high fabric mass ink with an optimally processed yarn. This property can be gauged with the use of the “ink donut” as described in the ink gloss and smoothness. Or for a more quantifiable measure, one can measure the L*a*b* of the donut and then the direct printed garment with a colorimeter to find delta-e and use the following equation to solve for the failure to matte-down the fibers of the garment. The formula to account for percentage change = (∆1 - ∆2) ¸ (∆1 + ∆2).
Ink rheology: There are at least four elements of the flow properties of the ink which affect how we transfer the print and its final attributes: viscosity, tack, fluid momentum, and surface tension. Viscosity is the thickness or thinness of the ink which drops immediately with an increase in stroke speed. Tack is a ratio of how the ink sticks to itself versus how it sticks to another surface. It doesn’t diminish very fast with an increase in speed and causes the most issues on press. Fluid momentum, or how long the ink flows, once it leaves the blade is crucial to penetration or the absence of penetration, and surface energy is how the gelled ink accepts another color and how quickly that color can attach to the gelled ink. A viscometer, rheometer, and tensiometer will allow for the quantification of the flow properties of the ink but for those on a budget. Insert a flexible metal spatula 3" deep into the ink at one edge of a five of white. Immediately drag the blade to the opposite edge, the difference in the channel from one edge to the other is the viscosity, the bend of the flexible spatula is the tack. The time the first edge takes to fill the cut channel represents the fluid momentum and the edge-acuity of the channel references the surface tension. Finally, use a nine-zone to find optimal gap, blade angle, pressure, and speed.
Ink brightness and opacity: Testing for ink brightness and opacity attributes is similar to ink matte-down versus fibrillation. Use the donut of ink as described in the above section and compare the brightness and opacity to the direct printed garment. The instrumentation which would enable us to quantify the differences are a densitometer or a colorimeter.
Press calibration and ink evaluation: There are off-contact distance gauges, digital levels, accelerometers, and pitch gauges which are all very valuable if one wants to fine tune the press. The manufacturer of the press will have these tools when they visit your facility for annual calibration and preventative maintenance. However, since we are trying to appeal to all budgets, if you have this complement of instrumentation, then run a nine-zone to verify calibration. If the right tools are unavailable then you can build an in-house nine-zone file or film image. Let’s keep the math simple and say your maximum printable image is 15" X 15". Each of the nine zones would measure 5" X 5"—three rows and three columns. Each zone should contain a long tonal range visual image, a solid area and a stair-stepped solids of 75, 50, and 5 to 15 percent tints, all in a viable line count for our mesh and stencil preferences.
As we are business people, the “thrill of victory and the agony of defeat” is best measured at the bank in terms of net operating profit. Whatever our motivation, cost containment or revenue enhancement profit, is the report card to tell us if we won or lost. If we consider the cost of the capital equipment and the severity of liability accessorizing becomes a no-brainer. Nonetheless we may just not have the budget to do it all today. We should take the guidelines herein, define what lights us up and then build a list of test procedures for calibration and monitoring in a sequence of sprinkles we can live with.