Screen PrintingScreen Printing

Main AdvantagesMain Advantages

• Can be printed on a wide variety of Can be printed on a wide variety of materials.materials.

• Preferred over other methods, Preferred over other methods, because of its low cost.because of its low cost.

FramesFrames• MaterialsMaterials

– Wood– less expensive, warps or rots fasterWood– less expensive, warps or rots faster– Aluminum– more expensive, durableAluminum– more expensive, durable

• SizesSizes– Labeled according to I.D. (inside dimension)Labeled according to I.D. (inside dimension)

• Recommended sizes for printing: at least Recommended sizes for printing: at least 66 inches inches beyond.beyond.

• Image size at top and bottom: at least Image size at top and bottom: at least 66 inches on each inches on each side. side.

• TypesTypes– Wooden with groove: made for attaching fabric Wooden with groove: made for attaching fabric

with a with a roperope..– Wooden or aluminum without a groove: fabric Wooden or aluminum without a groove: fabric

attached with glue.attached with glue.– Retensionable aluminum: screen can be tightened Retensionable aluminum: screen can be tightened

repeatedly.repeatedly.

FabricsFabrics

• Two main functionsTwo main functions– Provide support for stencil.Provide support for stencil.– Control ink flow. 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. meshFine 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. meshCoarse 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 opacityBetter opacity

Fabrics cont…Fabrics cont…

• Two general typesTwo general types– Multifilament: tiny strands twisted togetherMultifilament: tiny strands twisted together

• Includes: Includes: polyesterpolyester and silk and silk

• Good for film stencils (like amber film)—sticks to it Good for film stencils (like amber film)—sticks to it betterbetter

– Monofilament: (mono= Monofilament: (mono= oneone) single strand of ) single strand of threadthread• Good for liquid emulsionGood for liquid emulsion

• Includes polyester; stainless steelIncludes polyester; stainless steel

• Good for fine detail; easier to clean than Good for fine detail; easier to clean than multifilamentmultifilament

Fabrics cont…Fabrics cont…

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

Stencils (Two Types)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) Photographic: (light sensitive) photophoto emulsionemulsion (liquid) (liquid)

– Exposure process: Some type of light is used to harden Exposure process: Some type of light is used to harden emulsion.emulsion.• Why does the image spray out?- Why does the image spray out?- The particles in the emulsion that The particles in the emulsion that

the positive was not covering, was hardened by the UV light.the positive was not covering, was hardened by the UV light.

– Overexposure: results in image NOT spraying out completely.Overexposure: results in image NOT spraying out completely.

– Underexposure: results in Underexposure: results in scummingscumming (an almost invisible film (an almost invisible film forms on stencil from the still soft emulsion running across forms on stencil from the still soft emulsion running across screen as it dries)screen as it dries)

Exposure Process cont…Exposure Process cont…

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

Exposure Process cont…Exposure Process cont…

• Positive: Must be Positive: Must be made right reading with made right reading with high density to UV-A illuminationhigh density to UV-A illumination

• Screen preparation: Screen preparation: degreaserdegreaser is applied is applied to remove any oils or solvents from the to remove any oils or solvents from the fabric so emulsion will go on without flaws.fabric so emulsion will go on without flaws.

• Exposure times vary with:Exposure times vary with:– Thickness of emulsion (also how many coats)Thickness of emulsion (also how many coats)– Mesh countMesh count– Type of exposure unitType of exposure unit

InksInks

• Consist of…Consist of…– Pigment--- provides the Pigment--- provides the colorcolor– Vehicle--- gives it “bulk”Vehicle--- gives it “bulk”– Solvent--- makes it flow, then Solvent--- makes it flow, then

evaporates, leaving the rest of the ink evaporates, leaving the rest of the ink behindbehind

– Modifiers--- examples: thinners; Modifiers--- examples: thinners; phoshluorescents; puff agents; etc.phoshluorescents; puff agents; etc.

Types of InkTypes of Ink

• Conventional– dry by Conventional– dry by airair– Water basedWater based– Solvent basedSolvent based

• Non-conventional– cured by Non-conventional– cured by “polymerization” “polymerization” – Plastisol– cured with heat (325 degrees); used for Plastisol– cured with heat (325 degrees); used for

absorbent materials only (textiles); won’t work absorbent materials only (textiles); won’t work on paper, except for heat transfers.on paper, except for heat transfers.

• UV (ultraviolet) inks– cured with UV light; UV (ultraviolet) inks– cured with UV light; for non-absorbent substrates such as for non-absorbent substrates such as vinylvinyl, , and coated papers. Quick, clean method.and coated papers. Quick, clean method.

Inks cont…Inks cont…

• Process inks vs. spot colorsProcess inks vs. spot colors– Process inks- ________, ________, Process inks- ________, ________,

_______,________ combined to produce _______,________ combined to produce full color prints. Process inks have less full color prints. Process inks have less “opacity.”“opacity.”

– Spot color– one or more colors to Spot color– one or more colors to improve appearance without expense of improve appearance without expense of process printing (or could be a special process printing (or could be a special color added to a process print)color added to a process print)

Squeegees Squeegees

• Three main purposesThree main purposes– Force ink through meshForce ink through mesh– ““Flood” stroke: purposeFlood” stroke: purpose

•A. ______________________A. ______________________•B. ______________________B. ______________________

– Control ink deposit:Control ink deposit:•Low angle=_______________Low angle=_______________•Slow speed=______________Slow speed=______________•More pressure=____________More pressure=____________

Squeegees cont…Squeegees cont…

• Recommended size: two inches wider Recommended size: two inches wider than image width (maximum)than image width (maximum)

• Storage: Blade upStorage: Blade up• Blades vary in:Blades vary in:

– Material: vinyl or rubberMaterial: vinyl or rubber– Hardness: durometer rating (the higher Hardness: durometer rating (the higher

the rating, the stiffer the blade)the rating, the stiffer the blade)– Shape: Shape:

Squeegee cont…Squeegee cont…

• Clean-upClean-up– Water based ink- cleans up with Water based ink- cleans up with Water!!Water!!– Plastisols require __________ (paint Plastisols require __________ (paint

thinner) or other specially made ink thinner) or other specially made ink cleaning solutions. cleaning solutions.

– Liquid (direct) emulsion– remove by Liquid (direct) emulsion– remove by degreasing first to get rid of ink solvents degreasing first to get rid of ink solvents left behind, then apply reclaimer.left behind, then apply reclaimer.

Terms to Know!Terms to Know!

• Trapping:Trapping:

• Off-contact:Off-contact:

• Halations: Halations:

• Scumming:Scumming:

• Haze:Haze:

• Platen:Platen:

Terms to Know cont…Terms to Know cont…

• Substrate:Substrate:

• On-contact:On-contact:

• Opacity:Opacity:

• Reclaim:Reclaim:

• Register guide:Register guide:

• Durometer rating:Durometer rating: