Packaging Paper Grades Explained: Kraft, MG, Greaseproof, Cupstock and Liners

Packaging paper grades at a glance

Paper grades fall into four practical families: kraft papers for bags and sacks, thin barrier papers for wraps and food bags, paperboards for cups and cartons, and containerboard for corrugated packaging. The table below maps each grade to its typical weight range and the products it usually ends up in. Ranges are indicative; mills publish their own grammage steps. Lightweight tissue, used for wrapping and napkins, is a separate family; the tissue paper grades are covered in their own guide.

What are the main types of kraft paper?

Kraft paper is any paper made from chemical pulp produced by the kraft (sulphate) process, which keeps fibres long and strong. Buyers usually meet it in three forms: sack kraft, MF kraft and MG kraft, each available in brown (unbleached), white (bleached) and recycled-content versions.

The name comes from the German word for strength, and in German specifications you will see Kraftpapier with weight quoted as Grammatur in g/m². What separates the sub-types is the finish applied on the paper machine and how much fibre is in the sheet.

Sack kraft

Sack kraft is built for tensile energy absorption (TEA): the ability to stretch and absorb a drop impact without tearing. Extensible grades are micro-creped on the machine so they can elongate several percent before failure. They are also porous, so filled cement or flour sacks can de-aerate. For printed retail packaging sack kraft is rarely needed, but it sets the benchmark for what "strong kraft" means.

MF (machine finished) kraft

MF kraft has the same matt texture on both sides. It is the workhorse for handled carrier bags and SOS (self-opening square) bags, typically from around 50-80 gsm for SOS and light takeaway bags up to 120-150 gsm for heavier retail bags. The open surface gives a natural look but absorbs ink, so fine screens and small reversed text are harder to hold. How to match weight to load is covered in the paper bag GSM guide.

MG (machine glazed) kraft

MG paper is dried against a large, polished, steam-heated cylinder (the Yankee cylinder). The side that touches the cylinder comes out smooth and glossy; the other side stays rough. MG papers are usually thin, around 25-60 gsm, and are the standard base for counter bags, sandwich and bakery bags, and many food wraps. The glazed side prints sharper than MF kraft and gives a slightly better barrier to grease and moisture, though on its own it is not greaseproof.

Brown, white and recycled kraft

Unbleached (brown) kraft keeps the lignin colour of the pulp and is typically the strongest option for a given weight. Bleached (white) kraft gives a cleaner print base and brighter colours at a small cost in strength and a higher price. Recycled kraft uses recovered fibre; its shade varies more from batch to batch and its strength per gram is lower, which is why recycled bags often need a heavier grammage. For the bag-specific decision, including how each looks when printed, see brown kraft vs white kraft vs recycled paper. For takeaway boxes the same choice applies to board: kraft vs white board takeaway boxes.

Greaseproof, grease-resistant and glassine: what is the difference?

Greaseproof paper resists fat because its fibres are refined so heavily that the sheet becomes dense with very few pores. Grease-resistant paper gets its resistance from a coating or surface treatment on an ordinary base paper. Glassine is greaseproof paper that has been supercalendered (pressed between polished rolls) until it is smooth and translucent.

The distinction matters for three reasons. First, performance: a dense greaseproof sheet holds out fat throughout its thickness, while a coated paper depends on an intact coating, so fold lines and creases can become weak points. Second, recyclability and composting, which depend on what has been added. Third, chemistry: historically some grease-resistant papers used fluorochemical (PFAS) treatments. In the EU, Regulation (EU) 2025/40 (the PPWR) restricts PFAS in food-contact packaging from 12 August 2026, and several US states have their own bans; the PFAS-free food packaging guide covers limits and alternatives. When you request greaseproof or grease-resistant paper, ask for the grease-resistance level (usually as a KIT rating, explained in KIT test and grease resistance ratings) and for confirmation that no fluorochemicals are intentionally added.

In German, greaseproof paper is often sold as Pergamentersatz or fettdichtes Papier; in Dutch, vetvrij papier. These are not the same as true parchment or wax paper, which are compared in greaseproof vs parchment vs wax paper vs deli paper. Barrier coatings applied to paper (PE, aqueous dispersion, PLA, wax) are covered separately in barrier coatings for paper packaging.

What is cupstock and how is it different from carton board?

Cupstock is paperboard made specifically to be formed into cups and round containers. It is typically 170-350 gsm, made from virgin fibre, internally sized so liquid does not wick into the cut edges, and coated on the inside (and on both sides for cold cups) with PE or an aqueous dispersion barrier.

Folding carton boards (FBB, SBS and WLC) look similar on the surface but are not designed for heat-sealing, side-seam forming or prolonged contact with hot liquid. Cupstock also has to tolerate the bottom curl and rim roll that form the cup, which needs good fibre bonding. Single-wall hot cups typically sit at the heavier end of the range, cold cups and ice cream cups lower. Double-wall cups combine an inner cupstock cup with an outer sleeve wrap that may be a lighter board.

The lining is a separate specification from the board itself: see paper cup linings: PE vs aqueous dispersion vs PLA. For round food containers the same board family applies; see custom printed paper food containers.

If you are choosing board for printed retail cartons rather than cups, the comparison of folding boxboard, solid bleached board and white-lined chipboard lives in FBB vs SBS vs WLC. In short: SBS is fully bleached virgin fibre, FBB has a mechanical-pulp middle between chemical-pulp outer layers, and WLC is recycled with a white top.

Kraftliner vs testliner: which liner do you need?

Kraftliner is made mainly from virgin kraft fibre and delivers higher burst and compression strength per gram; testliner is made mainly from recycled fibre and is cheaper but needs more weight to reach the same strength. For a food-contact surface or a box that must stack under humid conditions, kraftliner is often specified; for dry transit and e-commerce boxes, testliner is common.

Corrugated board is a sandwich of liners and fluting, known in German as Wellpappe. The liners carry print and provide most of the bending stiffness and burst strength; the fluting provides thickness and compression resistance.

Pizza boxes are the classic food example: the inner liner touches a hot, fatty product, so the choice between virgin and recycled liner affects both performance and compliance documentation. Flute selection for that application is covered in E-flute vs B-flute pizza boxes; for e-commerce boxes, corrugated board grades for mailer boxes explains flutes, ECT and burst.

Fluting

Fluting (corrugating medium) is the paper that is heated, steamed and formed into flutes. Semi-chemical fluting uses virgin hardwood pulp and gives stiffer flutes and better crush resistance; recycled fluting (sometimes labelled Wellenstoff in German specifications) is the cost-driven alternative. Fluting is rarely printed or seen, but it decides how well a box stacks and how flat its printed surface stays.

GSM vs caliper vs bulk: which number should you specify?

Specify grammage (gsm) as the primary value because it is what the mill controls and what paper is traded on. Add caliper (thickness in µm) when stiffness, machine feeding or the feel of the pack matters, because two papers of the same gsm can differ in thickness by 20 % or more.

• Grammage (gsm, g/m²) is the mass of one square metre, measured to ISO 536. It drives material cost, since paper is bought by weight, and it is the basis for packaging-weight reporting under EPR schemes.
• Caliper is thickness, usually in micrometres (µm), measured to ISO 534. Boards are sometimes quoted in points (thousandths of an inch) in the US. Caliper strongly influences stiffness: bending stiffness rises roughly with the cube of thickness, which is why a bulkier board can feel much more rigid at the same weight.
• Bulk is caliper divided by grammage, expressed in cm³/g. A high-bulk board is thick for its weight; a low-bulk paper such as glassine is dense. Density is the inverse of bulk.

Practical consequences: a high-bulk board lets you reduce gsm for the same stiffness, cutting material weight. A dense paper usually prints sharper and resists grease better but feels thinner. When comparing quotations, check that both suppliers quote the same grammage and, for boards, comparable caliper; a lower price on a lower-caliper board is not a like-for-like offer. The packaging cost drivers guide covers quote comparison in more depth.

Which strength tests matter for packaging paper?

For most printed packaging four tests carry the specification: tensile strength (how much pull before breaking), tear resistance (how easily a started tear propagates), burst strength (resistance to pressure across the sheet) and water absorption (Cobb). Corrugated adds edge crush and compression tests.

Paper is anisotropic. Fibres align with the direction the paper travels through the machine (machine direction, MD), so tensile strength is higher in MD and tear resistance is usually higher across it (cross direction, CD). Data sheets quote both. For a carrier bag the handle load runs vertically, so the converter will orient the paper accordingly; for a wrap, folding behaviour differs by direction. If a supplier's data sheet gives only one value, ask which direction it refers to.

Humidity matters as much as the grade. Paper is tested at standard climate (23 °C, 50 % relative humidity under ISO 187), and strength drops noticeably when paper takes on moisture. Bags used for chilled or wet food, or boxes shipped in containers across climate zones, should be specified with that margin in mind.

Virgin vs recycled fibre: what changes for food contact?

Virgin fibre has a known history and gives more strength per gram; recycled fibre lowers material cost and environmental burden but can carry residues from its previous life, including mineral oil hydrocarbons (MOSH/MOAH) from printing inks. For direct food contact many buyers specify virgin fibre or require a functional barrier when recycled fibre is used.

In the EU there is no harmonised measure specific to paper and board in food contact. The general Framework Regulation (EC) 1935/2004 applies, and BfR Recommendation XXXVI (Germany) is widely used as the practical benchmark; buyers commonly expect a declaration of compliance referencing both. There is no binding EU limit for mineral oil in packaging at the time of writing, but recycled fibre and mineral-oil-based inks are recognised risk factors, which is why chains and food brands often set their own requirements. In the US, paper contacting food is covered by FDA rules such as 21 CFR 176.170 (aqueous and fatty foods) and 176.180 (dry foods).

Where recycled content is legally required, the picture reverses. California's SB 1053, for example, requires recycled paper carryout bags at covered stores to state their post-consumer content on the bag and to contain at least 50 % post-consumer recycled content from 1 January 2028, so a bag specification there must include it. Market-by-market bag rules are in paper bag regulations by market, and the full compliance picture is in food-contact packaging compliance in the EU, UK and US. For cartons, mineral oil barriers and food-safe cartons explains barrier options.

Which paper grade suits which product?

The table shows the grade that usually sits behind each format. Final material is always confirmed against the actual contents, filling method and target market during technical review.

Links to the product-level detail: custom printed takeaway bags, custom printed takeaway food boxes, grease-resistant food bags compared.

How to write the paper line of a specification

A paper line that a converter can quote without guessing has six parts. Use this checklist when preparing an enquiry, and see the packaging RFQ guide for the rest of the request.

• Grade name: for example "MG kraft", "greaseproof", "cupstock", "kraftliner/testliner".
• Grammage in gsm, with an acceptable tolerance if you have one, and caliper for boards.
• Colour and fibre: brown, white or recycled; virgin fibre required or not; any recycled-content minimum required by law in the destination market.
• Functional requirements: grease resistance (KIT level), water resistance (Cobb), lining or coating, strength targets where load matters.
• Food contact: whether the paper touches food directly, the type of food (dry, moist, fatty, hot) and the documentation you need.
• Print surface: which side is printed, and whether colour matching on a brown base is expected (see Pantone vs CMYK in packaging for what kraft does to colour).

If you are unsure which grade fits, describe the contents, how the pack is filled and used, and the markets it will be sold in. 9 Packaging is an Istanbul-based manufacturer and exporter of printed packaging for business customers, with experience in fast-food and chain-style foodservice packaging, and material recommendations are part of the technical review at quotation. Send your product details and any existing samples through our contact page.

Related reading

• Packaging glossary: paper, board, print and compliance terms
• Packaging Materials Glossary: Paper, Board, Corrugated, Films and Coatings

If a supplier quotes paper in US pounds rather than gsm, the paper weight converter converts by grade, because the factor depends on the basis sheet size.