In-line Flexo Printing Guidelines
Introduction for the bag buyer and packaging sales person
In our experience, most custom printed bag projects get started with people not trained to get the art ready - the person needing the bag and the packaging salesperson. It is important to have a basic understanding of what is needed to get a custom printed project off to a good start. Indications of plate costs and lead times we provide are based on receiving correctly prepared B&W or digital art work. The following are not “correctly prepared art”:
• Business cards, letterheads, photocopies, faxes, etc.
• B&W or scanned art requiring more than 150% enlargement.
• Previously printed paper bags or other packages.
• Overall designs not positioned on one of our bag templates.
• Films and/or plates not to our specifications.
• Multi-color designs with tight register and trapping requirements not prepared to in-line flexo specifications.
• Designs with halftones (photos) and/or flat screens requiring adjustment for in-line flexographic printing.
This is not to say it is impossible to complete a project with these materials - only that it may cost more and take more time.
Introduction for the graphic artist
Most artists and designers have a background in offset lithography, not flexography. If there is some flexo experience, it is in narrow web for labels, not the wide web used for paper packaging. These Art Guidelines are intended as a basic “how to” for designers and artists working on new flexographically printed shopping bag projects. The Guidelines should help to get the art done correctly the first time, minimizing prep expenses and prep time. If anything is unclear please ask.
In-line flexographic printing & bag making
Flexography is a relief printing process using photopolymer plates that are .112 thick. In many respects flexo is like printing with rubber stamps. Our printing is done in-line with the bag making. Rolls of paper are unwound into the bag machine, printed up to three colors, handles applied, side folds formed and seam glued, individual bag cut away from web of paper, bottom folded and pasted, and the finished bag is packaged for shipment. Click here to view a video of this process.
Ink color matching and proofing
• We use PMS colors specified, or can custom match submitted materials. Please specify colors from the uncoated “U” section.
• There is no charge for matching. GCMI colors are okay too.
• PMS ink color standards and formulations are per our ink supplier’s current PMS swatch book. Please specify the PMSU shade that best matches color(s) previously printed on coated paper. May be a different PMS #. There are PMSC colors that can not be matched on uncoated papers.
• Ink drawdowns for PMS colors on TULSAKRAFT™ VERSA (white side) and White Kraft sent only when requested on P.O., or when there are traps or overprints that should be approved prior to production. We send ink drawdowns for all PMS matches on Natural Kraft and TULSAKRAFT™ VERSA (natural side), as well as for custom matches to colors other than PMS. Approval is needed before bags can be produced.
With our commitment to environmentally friendly water based inks and limiting the non-recoverable waste generated in our plant, we offer only three metallic inks: Gold 872, Silver 877 and Copper 876. 10M minimum per item. Maximum coverage 50%, with upcharge. No custom metallic matches. Ask Customer Service about non-metallic matches to metallic colors, available without upcharge - the more sustainable ink alternative.
Design templates, logo positioning and bag proofing
Unless the design is no more than a spot print, the designer should have a template before starting artwork. Each bag size has its own template. Click here for templates. Orders for spot imprints not on a template must include logo size and positioning instructions on the P.O., e.g., “Enlarge to 6” wide, position center left to right, 3” up from bottom.”
All bags are proofed, usually as a folded one color blueprint, with different shades used to differentiate multiple colors, and/or screens of one color. These blueprints do not show actual screens. When there are screens, a conventional dylux blueline will be burned from a negative for approval of the screens. Alternative proofs may be furnished when tight register and/or complicated trapping of multiple colors are involved. Bag proof approval is needed before production. Click here for a video about bag proofs on our Facebook page.
Continued top of next column
In-line Flexo Printing Guidelines continued
Line width and type size
• Minimum positive printing line width: Two (2) point
• Minimum reverse printing line width: Three (3) point
• Minimum positive printing type size: Ten (10) point
• Minimum reverse printing type size: Twelve (12) point
These guidelines are subject to review with serif type faces, and with designs including areas of broad solid coverage along with small type in the same color. In these situations type/line may need to be larger and/or bolder. Think big for visual merchandising. Promote the brand to everyone who sees the bag, not just the person holding it. Bags are Walking Billboards.
Register tolerance and trap
Wherever two colors meet, a minimum 4.5 point - 1/16” - is required to trap the colors. Where two colors are adjacent and not to touch, there should be a minimum 4.5 points of space between them. As a general rule this register tolerance precludes the use of two overprinting colors to create a third color, whether with solids or screens. If attempted this would need a third color such as black to outline the shape.
Screens and halftones
• The line screen used in our process ranges between 45 and 55. The coarse screen is not apparent from typical viewing distance and insures cleanest possible dot reproduction. Due to the differences between how wide web flexo and offset litho reproduce screens and halftones, we request the opportunity to review the design elements to provide specific production art direction as early in the planning process as possible.
• Halftones must have strong contrast, as must steps between manually selected screen values of the same color. Subtle tone variations will not reproduce. Please have the artist contact us before going very far with a design using halftones and screens. We're happy to supply printed bag samples with halftones upon request.
Post Print & Hot Stamp Guidelines
Post printing and hot stamping are executed on bags after they are manufactured. Click here to view videos of these processes. There are limitations to these processes, including:
• Logos combining heavy coverage and reversed images may not print well. Positive images are preferred.
• Screens, borders and heavy coverage areas will likely distort when post printed over the folds of a bag. Click here for templates, fail safe tools to size art correctly and avoid the distorting areas of the bag.
• No metallic inks.
• Logos containing fine detail and small reverses will probably fill in when hot stamped. Enlarge these areas or consider post printing for a better result.
• Click here for typical art reproduced successfully in post printing and hot stamping.
• P.O. must specify logo size and positioning instructions, e.g., “Enlarge to 6” wide, position center left to right, 3” up from bottom.”
• Logos must be positioned at least 1” below the handle/patch.
• Specifications to center top to bottom may be adjusted to “center best” when true center will cause image quality problems due to folds, patches, handles, etc.
• Exact registration between two or more colors can not be maintained. Variation from perfect registration may range 1/8” to 1/2” depending on the product and process.
• Screening limited to 30% density at 30 line screen.
• We strive to produce the highest quality in our printing and hot stamping. Changes will be suggested when necessary to achieve a quality job within the capabilities of our processes and the materials available.
• Click here for copy size guide. Substrate and design combinations may reduce size capability.
Supplied artwork formats that work best
• Adobe Illustrator or high resolution PDF files preferred.
• Original vector art.
• Camera ready mechanical or scanned (raster) digital images that do not have to be enlarged more than 150%.
• CD for Mac or CD/DVD for PC.
• As email attachments to email@example.com or firstname.lastname@example.org. Typical maximum as email attachment is 7 to 10 megabytes. We use Stuffit compression utility.
• With digital art please send all fonts and image source files and confirming PDF or hard copy - scaled laser or ink jet print, etc. - indicating correct output.
•.007 RREU (right reading emulsion up) negatives. Please do not supply negatives for designs with screens and/or halftones.
•.112 photopolymer plates with .050 relief. Please do not try to furnish plates for designs with screens and/or halftones. Plates already mounted on sticky back can not be used.
•.250 Magnesium dies for hot stamping, .0625 to .09375 relief.
• All supplied production materials subject to review for quality and suitability in our process. Supplied plates and/or dies must be accompanied by film negatives.