Printwear

Recognized Supplier Guide ‘18

For the Business of Apparel Decorating

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38 || P RI N T W E A R O C T O B E R 2 01 8 s mall areas will wash a way after exposure. The result is pinholes. Even if the light scatters around the m, hardening the m within the e mulsion, they will act as "irri - tants" under the exing of the fabric and stencil during printing, causing the sten- cil to wear pre maturely and ink to pass through. The result is on-press pinholes. 4. Shop cleanliness is essential to avoid- ing pinholes. Keep a container of glass cleaner near your exposure unit and use it. Wipe your positives before each shot. Dirt and dust specks may be "resolved" by your stencil as pinholes. 5. Be sure to " ll" the mesh openings co m- pletely with e mulsion during coating. E mulsion must be pushed into the mesh, not si mply scraped across the fabric. We reco m mend the use of a scoop coater or coating trough to apply e mulsion. Use slo w, s mooth strokes. 6. It is i mportant that the e mulsion be co m- pletely dry, through and through, before exposure. Still- wet e mulsion inside a dry outer "skin" of e mulsion cannot harden properly. Pinholes will result. Be especial- ly careful of this during su m merti me heat and hu midity. Also, be sure that your fabric is co mpletely dry before you begin coating, follo wing the degreasing rinse. 7. A major cause of pinholes is si mple underexposure. During stencil washout, feel the inside or squeegee side of the screen. If it feels sli my and wet, insuf cient light energy has been trans mitted to harden the e mulsion on the inside of the screen. It is underexposed thus causing pinholes during printing. If you add additional coatings of e mulsion, increase your exposure. Dyed fabric, stainless mesh, and coarse fabric also require additional exposure ti me. 8. Store e mulsion properly. Write the date of sensitizing on the label and refer to the storage infor mation fro m the manufacturer. If at all possible, refrigerate e mulsions for maxi mu m sensitized storage life. If you return unused e mulsion fro m your scoop coater back into the e mulsion container, be sure it hasn't picked up shop dirt and dust. Pinholes are not unavoidable. By checking your shop's procedures against the above list of causes you can eli minate pinholes. TAYLOR LANDESMAN, LAWSON SCREEN & DIGITAL PRODUCTS What should I look for in a haze remover to remove ghost images? There are t wo i mportant characteristics that a haze re mover should de monstrate. First, the product should be of a thick consistency, so that when applied onto a wet screen, it will stay put. This will allo w the active co mponents to effectively dissolve the ghost i mage without affecting the integrity of the bond of mesh to the screen fra me. The second attribute is that the product can re main on the screen without da maging the mesh. SHELLEY MARKUS, RHINOTECH How can I test a plastisol screen print for proper cure? The ulti mate and de nitive test to deter mine if plastisol inks are properly cured is a wash test. Wash the gar ment in hot water with a strong detergent. Generally, it will take fro m ve to 10 washings to fully test the cure, but if the ink is seriously under-cured, the print will sho w deterioration after only one to three washings. There are t wo other test methods that are co m monly used to check for plastisol cure. The most popular test is the Stretch Test. Stretch the print about t wo-thirds of the total stretch of the T-shirt. If the print cracks and does not retract when the fab- ric is released, the ink is probably under- cured. The stretch test does not al ways work on really thick deposits of ink, such as athletic jerseys, where the top layer of ink may stretch but deeper layers may be under-cured. Another test for curing is the "Ethyl Acetate Test". Place a fe w drops of ethyl acetate onto the back of the ink on the inside of the gar ment. This spot of ink is then placed onto an area of the unprinted gar ment and then tightly held together for t wo minutes. If there is a transfer of ink to The "dual" in dual cure means that the e mulsion uses t wo sensitizers. One is already in the e mulsion before mixing, and the other is usually a diazo that is added to the e mulsion by the user. (I mage courtesy La wson Screen & Digital Products)

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