In short: FBB (folding boxboard) gives the most stiffness per gram and suits most food and retail cartons; SBS (solid bleached board) gives the whitest, smoothest surface for premium finishing; WLC (white lined chipboard) is the low-cost recycled option for non-food cartons or food behind a functional barrier. The grade also explains why carton quotes for the same design can differ widely: one may specify recycled WLC at 350 gsm, another virgin FBB at 295 gsm, and the two cartons can feel equally rigid in the hand. Below, the grade codes are decoded, the caliper versus grammage question is explained, and decision rules are set out for food, premium and cost-led cartons. It sits within our custom printed folding cartons hub, which covers styles, printing and ordering.
What do FBB, SBS, WLC, GC1, GC2 and GD2 mean?
They are trade names and standard codes for classes of carton board. FBB (folding boxboard, GC1/GC2) is multi-ply virgin-fibre board with a bulky mechanical pulp middle. SBS or SBB (solid bleached board, GZ) is bleached chemical pulp throughout. WLC (white lined chipboard, GD/GT) is recycled-fibre board with a white top. The letter codes come from DIN 19303, the German standard widely used across Europe to classify paperboard.
In the DIN 19303 codes, the first letter G means a pigment-coated top surface (U would mean uncoated). The second letter gives the main furnish, and the number gives a sub-class.
| Code | Common name | Furnish | Reverse side | US equivalent term |
|---|---|---|---|---|
| GZ | SBS / SBB, solid bleached board | Bleached chemical pulp in all plies | White | SBS (solid bleached sulphate) |
| GC1 | FBB, folding boxboard | Bleached chemical pulp outer plies, mechanical pulp middle | White | Often grouped with SBS or sold as FBB |
| GC2 | FBB, folding boxboard | As GC1 | Cream (manila) | FBB |
| GT1 / GT2 / GT3 | WLC with white or cream back | Recycled fibre with white top liner | White or cream | CRB (coated recycled board), white back |
| GD1 / GD2 / GD3 | WLC with grey back | Recycled fibre with white top liner | Grey | CRB, grey back |
| (no single DIN code used here) | CKB / CUK, SUS | Unbleached virgin kraft, sometimes white-coated top | Brown | CUK (coated unbleached kraft), SUS |
Within GD and GT, the number broadly describes bulk: GD1 is higher bulk, GD2 is the common standard grade and GD3 is lower bulk. GD2 is the grade most often meant when a quotation simply says "WLC" or "Chromoersatzkarton" in German-language specifications.
Mills sell branded products within each class, and two GC1 boards from different mills can differ in brightness, bulk and surface. Treat the code as the class and the mill data sheet as the specification.
FBB vs SBS: which virgin board fits your carton?
Choose FBB when you want high stiffness at a low grammage and a clean virgin-fibre surface at a moderate cost. Choose SBS when the carton needs the whitest, smoothest surface on both sides, very fine embossing or foil detail, or a premium feel through dense, uniform fibre. Both are made from virgin fibre and widely used for food.
FBB's advantage is structural. Its outer plies of bleached chemical pulp are strong and smooth, while the mechanical pulp middle is bulky. Like an I-beam, this construction places strong layers far apart, which raises bending stiffness relative to weight. In practice, FBB reaches the same rigidity as SBS or WLC at a lower grammage, which saves fibre, carton weight and freight.
SBS is denser. It is less stiff per gram than FBB but has a uniform cross-section of bleached fibre that takes deep embossing, crisp die-cutting and fine foil without cracking, and it is white on both sides. It is the traditional choice for luxury cosmetics, fragrance, pharmaceuticals and premium chocolate. In the US market, SBS is the default term for high-quality virgin carton board.
| Property | FBB (GC1/GC2) | SBS / SBB (GZ) |
|---|---|---|
| Fibre | Virgin, layered (chemical outer, mechanical middle) | Virgin bleached chemical pulp throughout |
| Stiffness per gram | Higher | Lower |
| Caliper at a given gsm | Higher (bulkier) | Lower (denser) |
| Top surface | Bright, coated | Very bright, very smooth |
| Reverse | White (GC1) or cream (GC2) | White |
| Embossing and fine foil | Good | Very good |
| Typical relative cost | Moderate | Higher |
| Typical uses | Confectionery, frozen food, cosmetics, pharma, dry food | Luxury and premium cartons, cosmetics, pharma, chocolate |
When does recycled WLC make sense?
WLC suits non-food retail cartons and food cartons where a functional barrier separates the board from the food. It is usually the lowest-cost carton board per tonne and uses recovered fibre, but it is less stiff per gram, so cartons often need a higher grammage to match FBB rigidity. Its recycled fibre can carry mineral oil and other residues, which limits direct use with many foods.
Typical WLC applications include toys, household and hardware products, shoe boxes, games, detergent cartons and other non-food retail. In food, WLC appears as outer cartons for products in sealed inner packs with a suitable barrier. Grey-back GD2 is the economy choice; white-back GT gives a better inside appearance for inside print or reveal panels.
Two practical points are often missed:
- Heavier grammage partly offsets the price advantage. If WLC needs 350 gsm to match a 295 gsm FBB carton, the board cost gap narrows and the carton weighs more, which affects freight and weight-based EPR fees.
- The print surface is coated and prints well, but whiteness and smoothness are typically slightly lower than virgin board, which can show in large light-coloured areas.
Why does grammage alone mislead?
Because carton rigidity depends much more on caliper (thickness) and ply structure than on grammage (mass per square metre), because bending stiffness rises roughly with the cube of thickness. That is why a bulky board at lower gsm can match or beat a dense board at higher gsm.
The ratio of thickness to grammage is called bulk (cm³/g). The ranges below are indicative and vary by mill and product.
| Board | Typical bulk (cm³/g) | Indicative caliper at 300 gsm |
|---|---|---|
| FBB (GC1/GC2) | about 1.4 to 1.7 | about 420 to 510 µm (roughly 17 to 20 pt) |
| SBS / SBB (GZ) | about 1.2 to 1.35 | about 360 to 400 µm (roughly 14 to 16 pt) |
| WLC (GD2) | about 1.3 to 1.5 | about 390 to 450 µm (roughly 15 to 18 pt) |
US converters specify caliper in points, where 1 pt equals 0.001 inch (25.4 µm). An "18 pt SBS" carton is about 457 µm thick. European specifications more often state grammage plus caliper. When comparing quotations from different markets, convert to caliper and ask for the mill's bending stiffness values (measured in mN, typically in both machine and cross direction), especially for large panels or heavy products.
Fibre direction matters too. Board is stiffer in the machine direction than across it, so the converter sets the grain direction on the dieline to suit the carton's main panels and creases.
Which boards are suitable for food cartons?
Virgin-fibre FBB and SBS are the usual choice for unwrapped, fatty, odour-sensitive or long-shelf-life food, because their controlled furnish keeps contaminants, odour and taint low. Recycled WLC is commonly used for food only where a functional barrier, such as a suitable inner bag or a barrier layer in the board, protects the food.
The concerns with recycled fibre for food are mineral oil hydrocarbons (MOSH and MOAH) from printing inks in the recovered paper stream, and other residues such as plasticisers and photoinitiators. They can migrate through the gas phase into dry food over months of storage. This is explained, with barrier options, in mineral oil barriers and food-safe cartons.
Regardless of grade, food cartons in the EU fall under Regulation (EC) 1935/2004 and the GMP Regulation (EC) 2023/2006. There is no harmonised EU measure for paper and board, so buyers typically ask the board mill and converter for a declaration referencing BfR Recommendation XXXVI. Sensory testing for odour and taint under the EN 1230 series is a common requirement for chocolate and other sensitive products. The broader rules across the EU, UK and US are covered in food-contact packaging compliance.
Where does kraft board (CKB, SUS) fit?
Kraft board is the choice for moisture, cold and heavy loads. Unbleached kraft boards are the strongest option per gram for tear and burst resistance, and they tolerate moisture and cold storage better than most bleached boards. They are used for beverage multipacks, frozen and chilled food, heavy products and brands that want a natural brown look.
CKB or CUK has a white coated top on a brown kraft base, so it prints full colour on the outside and stays brown inside. Uncoated kraft board gives a natural look with more limited print vibrancy; colours print darker and less saturated on brown fibre, so white underprint or bolder designs are often used. For papers rather than boards (kraft paper for bags, MG, greaseproof), see packaging paper grades.
Which board should you start with?
| If your carton... | Start with |
|---|---|
| Holds unwrapped, fatty or odour-sensitive food (chocolate, pastries, tea) | FBB or SBS, with low-odour inks and coatings |
| Holds dry food with long shelf life in direct contact | Virgin FBB/SBS, or recycled board only with a proven functional barrier |
| Needs a premium surface, deep embossing or fine foil | SBS (GZ) |
| Needs rigidity at the lowest carton weight | FBB (GC1 for white inside, GC2 if cream inside is acceptable) |
| Is non-food retail where cost per unit leads | WLC GD2; GT if the inside is visible or printed |
| Faces moisture, freezing or heavy loads | Kraft board (CKB/SUS) or a barrier-coated grade |
| Has a visible or printed inside | GC1, GZ or GT (white reverse) |
Is virgin or recycled board more sustainable?
Neither wins on every measure, so avoid broad claims either way. Recycled board uses recovered fibre and is usually cheaper; virgin board brings fresh fibre into the recycling loop and often achieves the same rigidity with less material. Both are widely recyclable in the paper stream when not laminated with plastic. Choose by product needs, then design for recyclability.
Weight matters under EPR schemes that charge by material weight, so a lighter FBB carton can offset some of the price gap to a heavier WLC carton. Any environmental statement on the carton itself must meet the rules on green claims; see recyclable, compostable and biodegradable claims.
What to state about board in a carton enquiry
- Grade class (GC1, GC2, GZ, GD2, GT, kraft) or a named mill product if you have one
- Grammage and target caliper, or the caliper of an existing carton you are matching
- Food contact: product type, direct or indirect contact, shelf life and storage temperature
- Whether a virgin-fibre or barrier board is required by your retailer or brand standard
- Reverse side: white, cream or grey acceptable, and whether there is inside print
- Finishing plans (deep embossing and fine foil favour SBS)
- Documents needed: food-contact declaration, mill certificates or test reports
Board is confirmed at quotation and technical review, often with a sample board or white sample to check rigidity. Continue with folding carton styles for structure, or return to the folding carton hub to complete the specification.