Screen Printing

Main Advantages Can be printed on a wide variety of materials. Can be printed on a wide variety of materials. Preferred over other methods, because of its low cost. Preferred over other methods, because of its low cost.

Frames Materials Materials –Wood– less expensive, warps or rots faster –Aluminum– more expensive, durable Sizes Sizes –Labeled according to I.D. (inside dimension) Recommended sizes for printing: at least 6 inches beyond. Recommended sizes for printing: at least 6 inches beyond. Image size at top and bottom: at least 6 inches on each side. Image size at top and bottom: at least 6 inches on each side. Types Types –Wooden with groove: made for attaching fabric with a rope. –Wooden or aluminum without a groove: fabric attached with glue. –Retensionable aluminum: screen can be tightened repeatedly.

Fabrics Two main functions Two main functions –Provide support for stencil. –Control ink flow. Mesh count: how many opening per inch. Mesh count: how many opening per inch. –Fine mesh=100 count (ct) up to 500 ct. mesh More detail and uses less ink; feels softer to touch. More detail and uses less ink; feels softer to touch. Less likely to smear on non-absorbent substrates. Less likely to smear on non-absorbent substrates. –Coarse mesh=40 to 100 ct. mesh Heavy ink deposit (good for light inks on dark shirts. Heavy ink deposit (good for light inks on dark shirts. Better opacity Better opacity

Fabrics cont… Two general types Two general types –Multifilament: tiny strands twisted together Includes: polyester and silk Includes: polyester and silk Good for film stencils (like amber film)—sticks to it better Good for film stencils (like amber film)—sticks to it better – Monofilament: (mono= one) single strand of thread Good for liquid emulsion Good for liquid emulsion Includes polyester; stainless steel Includes polyester; stainless steel Good for fine detail; easier to clean than multifilament Good for fine detail; easier to clean than multifilament

Fabrics cont… Colored Fabrics: used to reduce unwanted glare during exposure, called “halation’s.” Halation’s cause distortion around edge of images. Colored Fabrics: used to reduce unwanted glare during exposure, called “halation’s.” Halation’s cause distortion around edge of images.

Stencils (Two Types) Non-photographic: hand cut (i.e. amber film, or paper) Non-photographic: hand cut (i.e. amber film, or paper) Photographic: (light sensitive) photo emulsion (liquid) Photographic: (light sensitive) photo emulsion (liquid) –Exposure process: Some type of light is used to harden emulsion. Why does the image spray out?- The particles in the emulsion that the positive was not covering, was hardened by the UV light. Why does the image spray out?- The particles in the emulsion that the positive was not covering, was hardened by the UV light. –Overexposure: results in image NOT spraying out completely. –Underexposure: results in scumming (an almost invisible film forms on stencil from the still soft emulsion running across screen as it dries)

Exposure Process cont… Pinholes– tiny openings in the stencil caused by: Pinholes– tiny openings in the stencil caused by: –Poor positive (not opaque enough) –Too thin of emulsion –Screen poorly prepped –Bubbles in emulsion (do not shake!) –Dirt on exposure unit glass

Exposure Process cont… Positive: Must be made right reading with high density to UV-A illumination Positive: Must be made right reading with high density to UV-A illumination Screen preparation: degreaser is applied to remove any oils or solvents from the fabric so emulsion will go on without flaws. Screen preparation: degreaser is applied to remove any oils or solvents from the fabric so emulsion will go on without flaws. Exposure times vary with: Exposure times vary with: –Thickness of emulsion (also how many coats) –Mesh count –Type of exposure unit

Inks Consist of… Consist of… –Pigment--- provides the color –Vehicle--- gives it “bulk” –Solvent--- makes it flow, then evaporates, leaving the rest of the ink behind –Modifiers--- examples: thinners; phoshluorescents; puff agents; etc.

Types of Ink Conventional– dry by air Conventional– dry by air –Water based –Solvent based Non-conventional– cured by “polymerization” Non-conventional– cured by “polymerization” –Plastisol– cured with heat (325 degrees); used for absorbent materials only (textiles); won’t work on paper, except for heat transfers. UV (ultraviolet) inks– cured with UV light; for non-absorbent substrates such as vinyl, and coated papers. Quick, clean method. UV (ultraviolet) inks– cured with UV light; for non-absorbent substrates such as vinyl, and coated papers. Quick, clean method.

Inks cont… Process inks vs. spot colors Process inks vs. spot colors –Process inks- ________, ________, _______,________ combined to produce full color prints. Process inks have less “opacity.” –Spot color– one or more colors to improve appearance without expense of process printing (or could be a special color added to a process print)

Squeegees Three main purposes Three main purposes –Force ink through mesh –“Flood” stroke: purpose A. ______________________ A. ______________________ B. ______________________ B. ______________________ – Control ink deposit: Low angle=_______________ Low angle=_______________ Slow speed=______________ Slow speed=______________ More pressure=____________ More pressure=____________

Squeegees cont… Recommended size: two inches wider than image width (maximum) Recommended size: two inches wider than image width (maximum) Storage: Blade up Storage: Blade up Blades vary in: Blades vary in: –Material: vinyl or rubber –Hardness: durometer rating (the higher the rating, the stiffer the blade) –Shape:

Squeegee cont… Clean-up Clean-up –Water based ink- cleans up with Water!! –Plastisols require __________ (paint thinner) or other specially made ink cleaning solutions. –Liquid (direct) emulsion– remove by degreasing first to get rid of ink solvents left behind, then apply reclaimer.

Terms to Know! Trapping: Trapping: Off-contact: Off-contact: Halations: Halations: Scumming: Scumming: Haze: Haze: Platen: Platen:

Terms to Know cont… Substrate: Substrate: On-contact: On-contact: Opacity: Opacity: Reclaim: Reclaim: Register guide: Register guide: Durometer rating: Durometer rating: