Pick the wrong paperboard grade and you’ll find out the hard way — either your box costs more than it needs to, or it cracks on the fold, tears in transit, or looks dull next to a competitor’s product on the shelf. Most folding cartons are built from one of three grades: SBS, CUK, and CRB. They look similar on a spec sheet but behave very differently once they’re converted into a real box.
This guide breaks down what each grade actually is, what it’s made from, the specifications you’ll see on a supplier’s data sheet, whether it’s recyclable, and which one fits your product, your budget, and your sustainability goals.
Quick Answer
Use SBS (Solid Bleached Sulfate) when you need bright-white, food-safe, premium print quality — cosmetics, pharma, and high-end retail. Use CUK (Coated Unbleached Kraft) when you need maximum strength and tear resistance — beverage carriers, frozen food, and heavy or bulky products. Use CRB (Coated Recycled Board) when cost and recycled content matter more than pristine looks — cereal, snack, and other lightweight dry-goods boxes. All three grades are widely recyclable through standard paper-recycling streams, provided they aren’t laminated with plastic film or heavy wax.
SBS (Solid Bleached Sulfate): What It Is and Its Specifications
SBS is made from 100% virgin bleached wood pulp, so it’s white all the way through, not just on the surface. That gives it the cleanest die-cut edges, the highest print clarity, and no risk of grey or brown showing through at a fold or a window cutout. It’s also the grade most commonly approved for direct food contact, which is why it shows up on everything from cosmetics boxes to pharmaceutical cartons to premium food packaging.
On a supplier’s spec sheet, SBS typically runs in the 200–400 gsm basis-weight range, which corresponds to roughly 12–28 pt caliper depending on coating and finish. It’s usually sold as C1S (coated one side — printable face only, uncoated reverse) or C2S (coated both sides, for cartons where the inside is also visible or printed). Because it’s a single, homogeneous ply of bleached fiber rather than a multi-ply laminate, it holds fine detail, foil stamping, and spot UV better than CUK or CRB — and it’s the grade suppliers mean when they call something ‘convertible’ SBS paperboard: board engineered to fold, score, and die-cut cleanly into a finished carton, rather than being used flat as a sheet stock like index or cover paper.
Is SBS Paperboard Recyclable?
Yes. Plain SBS — with no plastic lamination — is paper-based virgin fiber and is accepted in standard curbside paper/cardboard recycling in most municipalities, the same as other paperboard cartons. The one exception is SBS that’s been laminated or extrusion-coated with polyethylene or wax for moisture or grease resistance, which is common on some food and frozen packaging; that plastic layer can make the carton harder to recycle or ineligible in some local programs. If a recyclability claim matters for your packaging, confirm the exact coating with your supplier and check it against your target market’s recycling guidelines rather than assuming.
CUK Paperboard (Coated Unbleached Kraft): What It Is and Where CUK Board Is Used
CUK starts from virgin unbleached kraft pulp — the same tough natural fiber used in grocery bags — with a white clay-coated top surface and a visible brown/kraft back. That unbleached kraft layer is what gives CUK its reputation as the strongest common paperboard grade, with the best tear resistance and wet strength of the three.
CUK board typically runs heavier than SBS, often in the 230–450 gsm range, because the jobs it’s built for — beverage carriers (six-pack carton wraps), frozen food boxes, and detergent or other heavy dry-goods cartons — need to survive rough handling, moisture, or refrigeration rather than look flawless. Suppliers sometimes label the same grade SUS (solid unbleached sulfate); it’s the same board under a different name.
CRB Paperboard (Coated Recycled Board): Composition, CCNB/CCKB, and CRB vs. CRB Paper
CRB paperboard is built primarily from recycled fiber — old corrugated boxes, mixed office paper, and recovered newsprint and magazine stock — laid up in multiple plies (commonly five to nine) with a clay-coated white top surface for printing. Because the back typically stays grey (or sometimes recycled kraft brown), you’ll often see this grade called CCNB (Clay Coated News Back) or CCKB (Clay Coated Kraft Back); CRB is now the more common umbrella term for the same family of board.
‘CRB paper’ and ‘CRB board’ are used interchangeably in the trade, even though it’s technically a paperboard rather than a paper. Recycled fibers are shorter than virgin fibers, so CRB is generally less stiff per point of thickness and more prone to cracking at tight folds if scoring isn’t dialed in — but it’s the most budget-friendly and recycled-content-heavy of the three grades, which makes it a common choice for cereal, snack, and other everyday dry-goods cartons. Because it’s built from recovered fiber, CRB is itself widely recyclable, the same as SBS and CUK, as long as it isn’t plastic-laminated.
How to Choose the Right Grade for Your Box
Start with what the box has to survive. If your product is heavy, will be refrigerated or frozen, or ships loose in a case (bottles, cans, multipacks), lean toward CUK — its wet strength and tear resistance are the whole reason it exists. If your product is lightweight and mostly needs to look good on a shelf (a bag of chips, a box of pasta, a cereal box), CRB usually does the job at a lower cost.
Next, think about what the box is selling. If unboxing quality, brand perception, or food/pharma-grade cleanliness matter — cosmetics, skincare, supplements, premium snacks, electronics accessories — SBS’s bright, uniform white gives designers the cleanest canvas for foil stamping, spot UV, and detailed graphics, and it avoids any grey show-through at edges or windows.
Thickness is described in points, where one point equals one thousandth of an inch (so 16 pt = 0.016″). All three grades are commonly available in roughly the 10–28 pt range, so caliper alone won’t tell you which grade to use — it’s the fiber composition and coating that drive strength, appearance, and cost. Go up in caliper for structural rigidity on larger or heavier cartons, but choose the grade itself based on strength needs and finish, not thickness alone.
Finally, weigh cost and sustainability messaging together. SBS commands the highest price because of its virgin bleached fiber and finish; CUK sits in a similar or slightly lower price range but earns it through raw strength; CRB is typically the most affordable and carries the strongest recycled-content story, which matters if your brand highlights sustainability on-pack.
Tips / Common Mistakes
Don’t default to SBS just because it looks premium — if your product doesn’t need direct food contact or flawless print, CUK or CRB can hit the same functional goals for less money. Don’t assume a higher point (thickness) number automatically means a stronger box; a thick CRB carton can still underperform a thinner CUK one on tear resistance and moisture handling.
If your carton has tight folds, sharp creases, or a lot of die-cut detail, ask your supplier about crack resistance — CRB’s shorter recycled fibers make it more fold-sensitive than virgin grades, and your converter may need to adjust scoring or grain direction to compensate. And if food or pharma contact is involved, confirm the specific board’s food-contact compliance with your supplier rather than assuming — not every SBS or CUK stock is certified the same way.
SBS, CUK, and CRB paperboard grades FAQs
What is CRB paperboard?
CRB (Coated Recycled Board) is a paperboard made mostly from recycled fiber, laid up in several plies with a clay-coated white printing surface on top and a grey or kraft-colored back. It’s also known as CCNB or CCKB depending on the backer fiber.
What is CUK paperboard used for?
CUK (Coated Unbleached Kraft) is used where strength and moisture resistance matter most — beverage carriers, frozen food cartons, and heavy or bulky dry-goods boxes — because its unbleached kraft fiber gives it the best tear resistance and wet strength of the common carton grades.
Is SBS paperboard recyclable?
Yes, plain SBS is virgin paper fiber and is accepted in standard curbside paper/cardboard recycling in most areas. If the board has a plastic (polyethylene) or wax moisture-barrier coating, that layer can make it harder to recycle in some local programs, so check the specific coating with your supplier.
What does ‘SBS convertible paperboard’ mean?
It refers to SBS produced and finished specifically to be converted — folded, scored, glued, and die-cut — into a finished folding carton, as opposed to SBS-family stock sold flat for uses like index or cover sheets. Convertible grades are engineered for clean scoring and folding without cracking.
What are typical SBS paperboard specifications?
SBS commonly runs 200–400 gsm in basis weight, corresponding to roughly 12–28 pt caliper, and is sold as C1S (coated one side) or C2S (coated both sides) depending on whether the inside of the carton needs a printable or clean white surface.
What’s the difference between CRB paper and CRB board?
There isn’t a technical difference — ‘CRB paper’ and ‘CRB board’ refer to the same material. It’s correctly classified as a paperboard, not a paper, but suppliers and buyers use the terms interchangeably.
Is CUK board the same as kraft paper?
No. CUK shares its base fiber with kraft paper (unbleached virgin kraft pulp) but it’s a heavier, clay-coated paperboard built for folding cartons, typically 230–450 gsm, not the thinner uncoated kraft sheet used for bags.
Is CRB paperboard recyclable and made from recycled material?
Yes. CRB is built primarily from recovered fiber — old corrugated boxes, mixed office paper, and recovered newsprint — and, like SBS and CUK, it’s widely recyclable through standard paper streams as long as it isn’t laminated with plastic film.
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