Detailed Printing Process Guide
What is Flexographic Printing?
Flexographic printing (flexo) uses raised-image photopolymer or rubber plates mounted on rotating cylinders. It's the most common method for printing on flexible packaging materials like poly bags, cellophane, and kraft paper.
When to Use Flexo Printing:
- Preprint Flexo: For 4-6 colors, tight registration, fine halftones (65+ line screen), lamination, or UV varnish
- Tailprint Flexo: For 1-4 colors during bag conversion, loose registration acceptable (3/32" tolerance)
- Medium-to-high volume runs (10,000+ units)
- Coated and uncoated papers, plastic films
Flexo Print Quality: Resolution of 65-133 line screen depending on substrate. Expect 9-15% dot gain on coated papers, 12-15% on uncoated. Registration tolerance: ±3/64" for preprint, ±3/32" for tailprint.
Flexo Advantages:
- Fast production speeds (up to 800 meters/minute)
- Works on virtually any substrate (plastic, foil, paper, film)
- Water-based and UV-curable inks available (food-safe options)
- Cost-effective for moderate-to-large runs
What is Gravure Printing?
Gravure printing uses engraved metal cylinders with recessed cells that hold ink. It's a preprint-only process ideal for high-volume packaging requiring premium color strength and fine detail.
When to Use Gravure Printing:
- Large production runs (100,000+ units) to justify cylinder engraving costs
- Up to 7 colors on one side (or 5 outside + 2 inside simultaneously)
- Metallic inks (gravure delivers superior metallic finish)
- High-resolution images (150-175 line screen)
- Coated papers only (claycoat substrates)
Gravure Print Quality: Minimal dot gain (3% dot prints as 5-7%). Very tight registration with minimal traps required. Excellent for dark colors and metallics where ink density matters.
Gravure Advantages:
- Highest color strength and density (best for metallics)
- Finest detail reproduction (175 line screen)
- Can print inside and outside of bags in one pass
- Registered inside print (not random)
- Long-lasting engraved cylinders for repeat orders
What is Offset Printing?
Sheet-fed offset lithography prints from flat metal plates onto individual sheets (not rolls). It's a preprint-only method offering the highest print quality for premium packaging.
When to Use Offset Printing:
- Small-to-medium runs (1,000-50,000 units)
- Unlimited color capability (sheets can run through press multiple times)
- Photographic quality required (150-175 line screen)
- Extremely tight registration (±0.010")
- High-grade smooth paper stocks
Offset Print Quality: Minimal dot gain (1% dot compensation possible). Precise ink metering via 9 ink rollers produces thin, uniform ink film. Best for fine gradients and photographic images.
Offset Limitations:
- Dark colors and metallics may require "double bump" (printing twice) for adequate density
- Higher per-unit cost for large runs vs. gravure or flexo
- Sheet-fed only (not compatible with continuous roll-to-bag conversion)
Choosing the Right Printing Method
| Factor |
Flexo |
Gravure |
Offset |
| Best For |
Moderate runs, bags & film |
High-volume, premium color |
Small runs, photographic quality |
| Quantity Range |
10,000-500,000 |
100,000+ |
1,000-50,000 |
| Color Limit |
4-6 colors |
7 colors (5+2 duplex) |
Unlimited |
| Resolution |
65-133 line screen |
150-175 line screen |
150-175 line screen |
| Substrates |
All (paper, plastic, film, foil) |
Claycoat paper only |
High-grade paper sheets |
| Registration |
±3/64" to ±3/32" |
Very tight (minimal) |
Extremely tight (±0.010") |
| Metallic Inks |
Good |
Excellent |
Requires double bump |
| Setup Cost |
Low-Medium |
High (cylinder engraving) |
Low-Medium |
Frequently Asked Questions
What's the difference between preprint and tailprint?
Preprint means the material (paper or film roll) is printed before being converted into bags. This is required for 5+ colors, tight registration, lamination, or fine halftones. Tailprint (flexo only) prints during bag conversion—faster and cheaper but limited to 4 colors with loose registration.
Can I print on the inside of a bag?
Yes, with gravure printing. You can print up to 5 colors on the outside and 2 colors on the inside simultaneously. Inside print can be registered (aligned) with the outside image. Flexo and offset do not support inside printing.
Which method is best for metallic gold or silver ink?
Gravure delivers the strongest, most reflective metallics due to its recessed-cell ink transfer. Flexo metallics are adequate for most applications. Offset metallics often require a "double bump" (printing the color twice) to achieve satisfactory opacity and shine.
What resolution do I need for photos or gradients?
For photographic quality, use gravure or offset (both 150-175 line screen). Flexo can handle photos at 110-133 line screen on coated paper but expect visible dot gain. Provide vector artwork or high-res images (300+ DPI) for best results.
How much does custom printing cost?
Cost depends on quantity, colors, and method. Flexo and offset have lower setup costs ($200-800), making them economical for smaller runs. Gravure requires cylinder engraving ($2,000-5,000) but offers the lowest per-unit cost at high volumes. Request a quote with your specs for accurate pricing.
What file formats do you accept for printing?
We accept Adobe Illustrator (.AI), PDF (with embedded fonts), and EPS files. Provide artwork in CMYK color mode with 1/8" bleed. Include Pantone (PMS) color references for spot colors. Need design help? Our prepress team can assist—contact us at 570-709-0366.
Related Packaging Resources
Ready to print your custom packaging? Call 570-709-0366 or email [email protected] with your artwork, quantity, and substrate. We'll recommend the best printing method and provide a fast quote.
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