Paper and Board Grades for Packaging: SBS, GD2, Kraft, and How to Specify the Right Substrate

Substrate selection — the choice of paper or board on which packaging is printed — is one of the most consequential technical decisions in packaging production. The substrate determines how ink sits and absorbs, what finishes are achievable, the structural rigidity and stacking strength of the finished packaging, and the print quality ceiling for the job.

Brand owners and designers who specify substrates vaguely ("white card," "kraft paper," "recycled board") create ambiguity that printers resolve by using whatever they have on the press — which may or may not be appropriate for the job. Specifying substrates precisely is how you get the result you designed for.

How Board and Paper Are Described

Paper and board substrates are described by three key parameters:

Weight (gsm — grams per square metre). The weight of one square metre of the substrate in grams. Heavier board is thicker and more rigid. Common weights for folding carton packaging: 250–450gsm. Common weights for labels: 70–150gsm for paper; 50–100 micron (µm) thickness for film substrates (film is measured in micron, not gsm).

Caliper (thickness in micron or millimetres). Thickness is a separate measure from weight because different materials of the same weight may have different density and therefore different thickness. A high-bulk uncoated board may be thicker than a coated board of the same gsm. For structural packaging, caliper affects rigidity and stacking strength directly.

Surface treatment. Whether the substrate is coated (a clay or mineral coating applied to the surface for improved smoothness and print receptivity) or uncoated (the raw fibre surface, which absorbs ink differently). Coated surfaces produce sharper, more vivid print; uncoated surfaces produce a softer, more matte result and absorb more ink.

Primary Folding Carton Grades

SBS — Solid Bleached Sulphate (also called GC1 or FBB in European classification)

SBS is the premium standard for consumer-facing folding carton packaging. It is a fully bleached, multi-ply board with a bright white surface on both sides and typically a coated surface for print.

Characteristics:

• Bright white throughout (no grey or brown interior layer — the cross-section is uniform white)
• High stiffness-to-weight ratio — structurally efficient for its weight
• Excellent print surface — supports high-quality CMYK reproduction, halftone screens, fine detail
• Compatible with all standard print finishes (laminate, foil, emboss, spot UV)
• Higher cost than recycled board grades

Typical use: Premium cosmetics, pharmaceutical cartons, supplement packaging, confectionery, spirits outer cartons, and any consumer packaging where a bright white interior is visible (open box experiences) or where print quality is a primary concern.

Common weights: 250gsm, 300gsm, 350gsm, 400gsm. For small, rigid boxes (cosmetics, healthcare), 300–350gsm is typical. For larger boxes, 350–400gsm for adequate stiffness.

GD2 — Grey-Back Duplex Board (also called GD or recycled folding boxboard)

GD2 is a recycled-content board with a coated white surface (printable side) and a grey back (the interior of the folded box). It is less expensive than SBS and carries a higher recycled content (typically 50–80% recycled fibre).

Characteristics:

• White coated surface — print quality is generally good, though slightly below SBS on very high-quality jobs
• Grey interior layer — visible at the fold edges and on the interior of the box
• Lower cost than SBS
• Higher recycled content — environmentally preferable on this metric
• Slightly lower stiffness per weight compared to SBS

Typical use: Mid-tier consumer packaging, retail grocery packaging, general merchandise cartons, and any application where the grey interior is not visible to the consumer or not a negative signal.

Key consideration: For open-box experiences (a box where the interior is visible — gift boxes, display cartons) the grey interior of GD2 is visible and reads as economy. For closed boxes where the interior is not seen, GD2 is a sensible cost-saving specification.

Common weights: 300gsm, 350gsm, 400gsm, 450gsm. GD2 typically requires a higher gsm than SBS to achieve equivalent stiffness, partly explaining the common specification of 400–450gsm.

FBB — Folding Boxboard (also called GC2 or Cartonboard)

FBB is a hybrid: a board with mechanical pulp in the middle layer (which creates high bulk and stiffness) and bleached chemical pulp on the surface layers (which creates good print surface and a white appearance at the edge). Less expensive than SBS, better surface quality than GD2.

Characteristics:

• White surface and white edge (the cut edge appears lighter than GD2's grey edge)
• Good stiffness-to-weight ratio (the mechanical pulp middle layer contributes bulk)
• Print quality between SBS and GD2
• Cost between SBS and GD2

Typical use: Food packaging (biscuits, cereals, frozen food), mid-tier pharmaceutical, and consumer goods where white edge appearance is important but SBS cost is not justified.

Kraft and Uncoated Natural Board

Kraft board is unbleached, producing a characteristic brown or natural appearance. It is made from virgin or recycled wood pulp using the kraft process, which preserves the strength of the cellulose fibres — making kraft unusually strong for its weight.

Virgin kraft. Unbleached virgin fibre board, producing the characteristic warm brown associated with artisan, natural, and sustainable brand positioning. The brown colour is intrinsic to the material — it is not a coating or surface treatment. Print on kraft absorbs into the surface; colours appear more muted and earthy than on a coated white surface. For branded applications, this characteristic is often a design feature rather than a limitation.

Recycled kraft. Made from recycled brown corrugated board and waste paper. Similar appearance to virgin kraft, slightly more variable in colour and surface quality. Lower cost.

White kraft. Kraft board that has been bleached to a white surface while retaining the kraft structure. Provides the strength of kraft with a printable white surface. Less common than standard kraft or SBS; used for applications requiring kraft-level strength with white surface quality.

Uncoated white board. Not technically a kraft, but shares the characteristic of an uncoated surface. Absorbs ink fully, producing a soft, matte, tactile result. Common for artisan, premium-minimal, and Scandinavian-influenced brand aesthetics.

Label Substrates

Labels are applied to a container (glass, plastic, metal) via a pressure-sensitive adhesive. The face stock (the top layer that carries the print) is the label substrate.

Paper Face Stocks

Uncoated paper (35–100gsm): The standard for wine labels and artisan product labels. Absorbs ink to create a tactile, traditional appearance. Susceptible to moisture damage — not suitable for chilled or wet-environment applications without a laminate overcoat.

Coated paper (70–130gsm): Smooth clay-coated surface for sharper print. More moisture resistant than uncoated paper but still not waterproof without lamination.

Wet-strength paper: A paper substrate with wet-strength resin added, allowing it to resist moisture without tearing. Used for wine labels applied to ice-bucket chilled bottles without needing a film substrate.

Film Face Stocks

White BOPP (biaxially oriented polypropylene, 50–80µm): Waterproof, conformable, good print receptivity, clean white appearance. The standard for consumer goods labels on personal care, supplement, food, and cleaning products. More premium in appearance than paper; suitable for wet and cold environments.

Clear BOPP (50–80µm): Transparent film that creates a "no-label look" — the label appears to float on the container surface. Requires specific ink opacity for the design to be visible. Effective on glass and translucent containers.

Metallic BOPP (silver or gold): A metallised film that creates a metallic appearance without foil printing. Less expensive than printed metallic foil labels; more limited in finish quality. Common in mid-tier personal care and food.

PP (polypropylene, various gauges): Similar to BOPP, slightly more rigid. Common in pharmacy labels and outdoor-use applications where durability is important.

Corrugated Board Grades

Corrugated packaging (shipping boxes, retail display units) consists of a fluted medium layer sandwiched between liner layers.

Flute profiles. Corrugated board is described by its flute type:

• A flute: Large flutes (approximately 5mm), excellent cushioning, used for fragile goods
• B flute: Medium flutes (approximately 3mm), good stacking strength, the standard for most retail and shipping boxes
• C flute: Between A and B (approximately 4mm), good cushioning and stacking, common for FMCG shipping
• E flute: Small flutes (approximately 1.5mm), very smooth surface for litho printing, used for premium corrugated retail packaging, mailer boxes, and display units
• F flute / micro-flute: Very small flutes (approximately 0.75mm), used for fine corrugated packaging that approximates folding carton rigidity while retaining corrugated structure

Liner grades. The outer layers (liners) of corrugated board are graded by weight and quality:

• Kraftliner: Virgin kraft fibre, brown or white, strong
• Testliner: Recycled fibre liner, brown, lower cost, lower strength
• White top testliner / white top kraftliner: Brown liner with a white surface layer for improved print surface and appearance

Single-wall vs. double-wall. Standard corrugated is single-wall (one fluted medium, two liners). Double-wall (two fluted layers, three liners) provides much greater rigidity and crush resistance for heavy goods.

How to Specify Substrate in a Print Brief

The complete substrate specification for a folding carton brief:

300gsm SBS (Solid Bleached Sulphate), coated one side (C1S), to be printed on the coated face.

For a label brief:

80µm white BOPP, permanent adhesive, on 130gsm silicone-coated release liner.

For a corrugated mailer box:

E-flute corrugated single-wall, white top testliner external face, brown testliner internal face, 3mm caliper.

This level of specificity leaves nothing for the printer to assume — the substrate is either available and priced, or the printer will confirm an alternative and seek approval before proceeding.

FAQ

Can I specify a substrate that my printer doesn't stock? Yes, but it typically adds lead time (the printer must order it in) and may add cost if the quantity is below the supplier's minimum. Some specialist substrates — unusual kraft grades, very heavy board, specific film constructions — may require ordering well in advance of the print schedule. Identify substrate requirements early and confirm availability with the printer before finalising the production timeline.

What board grade should I use for premium packaging? SBS (300–350gsm) is the standard for premium consumer packaging. For the highest-tier applications — luxury cosmetics, premium spirits gift packaging — 350–400gsm SBS with foil and emboss finishing is typical. For sustainable premium positioning, a FSC-certified board grade (SBS or FBB from a certified mill) maintains quality while supporting environmental claims.

Does the board grade affect how finishes look? Yes, significantly. Foil stamping on SBS produces a cleaner, more defined metallic than foil on GD2, because SBS has a more uniform, smooth surface. Matte laminate on a coated board has a different tactile quality from matte laminate on an uncoated board — the former is smooth and dry; the latter has a slightly more textured quality. Embossing shows more definition on heavier board (350gsm+) than on lighter weight board.