Complete Prepress Knowledge for the Graphic Design and Printing Industry
II. Paper Knowledge
Paper selection affects ink absorption, color accuracy, sharpness, and the final printed effect. Understanding paper types and weights is essential in prepress.
1. Paper Composition
Paper is made from plant fibers mixed with chemicals and additives.
Main components:
• Fiber
Common sources:
- Wood pulp
- Cotton
- Bamboo
- Recycled fiber
Different fibers affect paper strength, brightness, and smoothness.
• FiberImprove:
- Opacity
- Flexibility
- Smoothness
- Printability
Examples:
- Calcium carbonate
- Kaolin clay
- Talc
• Sizing Agents
Increase water resistance and prevent ink bleeding.
Examples:
- Starch
- Resin
- Alum
• Dyes & Pigments
Used to control whiteness or add color.
2. Paper Formats
Paper for printing is available in two major forms:
(1) Sheet Paper (Cut Sheets)
Used in offset printing and general print shops.
Common international sizes (ISO 216):
- A4: 210 × 297 mm
- A3: 297 × 420 mm
- A2: 420 × 594 mm
- A1: 594 × 841 mm
- A0: 841 × 1189 mm
(2) Roll Paper
Used in high-speed web presses for:
- Newspapers
- Magazines
- Packaging
- Labels
3. Paper Weight (GSM)
Paper is graded by grams per square meter (gsm).
Common weights:
| Weight | Typical Use |
|---|---|
| 70–120 gsm | Text pages / book interiors |
| 150–200 gsm | Brochures, magazine covers |
| 250–350 gsm | Cards, high-end brochures |
| 400 gsm+ | Packaging / rigid boards |
Rule:
- ≤200 gsm = paper
- >200 gsm = paperboard
III. Prepress Layout, File Preparation & Printing Requirements
Prepress ensures that a digital design becomes a properly printed product without errors.
1. Document Setup
Before designing:
- Set the correct final page size
- Use CMYK color mode for printing
- Add 3–5 mm bleeds around all edges
- Maintain a safe zone away from edges
- Use correct resolution images
2. Image Requirements
- Print images must be 300 dpi
- Use TIFF, PSD, or high-quality JPEG
- Avoid low-resolution internet images
- Avoid mixing RGB images in a CMYK project