# Kraft paper > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Kraft_paper > Markdown URL: https://mediated.wiki/source/Kraft_paper.md > Source: https://en.wikipedia.org/wiki/Kraft_paper > Source revision: 1357002477 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Type of paper or paperboard "Craft paper" redirects here; not to be confused with [paper craft](/source/Paper_craft). This article needs more citations. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Kraft paper" – news · newspapers · books · scholar · JSTOR (October 2011) (Learn how and when to remove this message) A roll of kraft paper **Kraft paper** or **kraft**, also known as **brown paper**, is [paper](/source/Paper) or [paperboard](/source/Paperboard) (cardboard) produced from [chemical pulp](/source/Chemical_pulp) produced in the [kraft process](/source/Kraft_process). **Sack kraft paper** (or just **sack paper**) is a porous kraft paper with high [elasticity](/source/Elasticity_(physics)) and high tear resistance, designed for packaging products with high demands for strength and durability. ## Description Pulp produced by the kraft process is stronger than that made by other [pulping processes](/source/Wood_pulp#Wood_pulp); acidic [sulfite processes](/source/Sulfite_process) degrade [cellulose](/source/Cellulose) more, leading to weaker fibers, and mechanical pulping processes leave most of the [lignin](/source/Lignin) with the fibers, whereas kraft pulping removes most of the lignin present originally in the wood. Low lignin is important to the resulting strength of the paper, as the [hydrophobic](/source/Hydrophobic) nature of lignin interferes with the formation of the [hydrogen bonds](/source/Hydrogen_bonds) between cellulose (and [hemicellulose](/source/Hemicellulose)) in the fibers.[1] Kraft pulp is darker than other wood pulps, but it can be [bleached](/source/Bleaching_of_wood_pulp) to make very white pulp. Fully bleached kraft pulp is used to make high-quality paper where strength, whiteness, and resistance to yellowing are important. *Sack kraft paper* is a porous kraft paper with high [elasticity](/source/Elasticity_(physics)) and high tear resistance, designed for packaging products with high demands for strength and durability.[2] ## Name Kraft paper, and the [kraft process](/source/Kraft_process) used to produce it, are named from the German word *kraft*, meaning strength, in reference to its mechanical properties. This shares an origin with the English word *craft*, leading to [linguistic confusion](/source/Mondegreen) with paper intended for artistic uses and [paper craft](/source/Paper_craft). ## Manufacture Woodchips used for kraft paper production [Wood pulp](/source/Wood_pulp) for sack paper is made from [softwood](/source/Softwood) by the [kraft process](/source/Kraft_process). The long fibers provide the paper its strength and [wet strength chemicals](/source/Wet_strength) are added to even further improve the strength. Both white and brown grades are made. Sack paper is then produced on a [paper machine](/source/Paper_machine) from the wood pulp. The paper is [microcrepped](/source/Cr%C3%AApe_paper) to give porosity and elasticity. Microcrepping is done by drying with loose draws allowing it to shrink. This causes the paper to elongate 4% in the machine direction and 10% in the cross direction without breaking.[2] Machine direction elongation can be further improved by pressing between very elastic cylinders causing more microcrepping.[2] The paper may be coated with [polyethylene](/source/Polyethylene) (PE) to ensure an effective barrier against [moisture](/source/Moisture), [grease](/source/Petroleum) and [bacteria](/source/Bacteria), although recyclability is hindered. [Zein](/source/Zein) coatings are also water resistant but allow better recyclability.[3] A paper sack can be made of several layers of sack paper depending on the toughness needed. Kraft paper is produced on paper machines with moderate machine speeds. The raw material is normally [softwood](/source/Softwood) pulp from the kraft process. Maintaining a high effective sulfur ratio or sulfidity is important for the highest possible strength using the kraft process. The kraft process can use a wider range of fiber sources than most other pulping processes. All types of wood, including very resinous types like southern [pine](/source/Pine),[4] and non-wood species like [bamboo](/source/Bamboo) and [kenaf](/source/Kenaf) can be used in the kraft process.[5] ## Qualities - Normal kraft paper is strong and relatively coarse. It has high [tensile strength](/source/Tensile_strength). The [grammage](/source/Grammage) is normally 40–135 g/m2. - *Sack kraft paper*, or just *sack paper*, is a porous kraft paper with high elasticity and high tear resistance, designed for packaging products with high demands for strength and durability. - Absorbent kraft paper is made with controlled absorbency (i.e., a high degree of porosity). It is made of clean low [kappa](/source/Kappa_number) [hardwood](/source/Hardwood) kraft and has to have a good uniformity and formation. - *Spinning kraft paper* is an especially strong type of kraft paper with relatively low grammage (40 g/m2). This paper requires the best possible machine direction strength and cross machine elongation. This is done by high fiber orientation on the paper machine. - *Hunting cartridge paper* is a kraft paper used in [shotgun shells](/source/Shotgun_shell). This paper needs a high tensile strength in the machine direction, which is the axial direction of the cartridges. In the cross direction, the cartridge is supported by the gun-pipe, but a sufficient elongation is needed. The body of the cartridge is wound of a kraft paper of 80–120 g/m2, which is further covered by an outer sheet of 60–80 g/m2 with color and printing. - *Candy wrapping paper* and *twisting paper* are thin 30–40 g/m2 kraft papers and are mostly [flexo](/source/Flexo) or [offset printed](/source/Offset_printing). These papers require a good strength, with highly oriented fibers. Twisting paper is mostly opaque and often [supercalendered](/source/Supercalendered). ## Applications Kraft paper bags - As a plastic-hazard-free paper in [paper sacks](/source/Paper_sack) for cement, food, chemicals, consumer goods, flour bags etc. - Electrical insulation in large oil-filled [transformers](/source/Transformer) - [Paper grocery bags](/source/Paper_bag), [multiwall sacks](/source/Paper_sack), gift bags,[6] [envelopes](/source/Envelopes), [ring binders](/source/Ring_binder),[7] and other packaging - An inexpensive material for lining [particle boards](/source/Particle_board) - The base paper for [sandpaper](/source/Sandpaper) - As wrapping for [flower bouquets](/source/Flower_bouquet) - In [World War II](/source/World_War_II), for fabricating [drop tanks](/source/Drop_tank) - As a wrapping for the French dish [Gigot bitume](/source/Gigot_bitume), which consists of a leg of lamb wrapped in Kraft paper and cooked in hot asphalt ## See also - [Butcher paper](/source/Butcher_paper) - [Corrugated fiberboard](/source/Corrugated_fiberboard) - [Gift wrapping](/source/Gift_wrapping) - [Manila paper](/source/Manila_paper) - [Paper bag](/source/Paper_bag) - [Paper sack](/source/Paper_sack) - [Parchment paper](/source/Parchment_paper) ## References 1. **[^](#cite_ref-1)** Hubbe, Martin A.; Lucia, Lucian A. (2007). ["The "Love-Hate" Relationship Present in Lignocellulosic Materials"](https://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_2_4_534_535_Hubbe_Lucia_Love_and_Hate_Lignocellulosics). *BioResources*. **2** (4): 534–535. [doi](/source/Doi_(identifier)):[10.15376/biores.2.4.534-535](https://doi.org/10.15376%2Fbiores.2.4.534-535). Retrieved 2015-02-02. 1. ^ [***a***](#cite_ref-sack_2-0) [***b***](#cite_ref-sack_2-1) [***c***](#cite_ref-sack_2-2) Paulapuro, Hannu (2000). "5". *Paper and Board grades*. Papermaking Science and Technology. Vol. 18. Finland: Fapet Oy. pp. 121–122. [ISBN](/source/ISBN_(identifier)) [952-5216-18-7](https://en.wikipedia.org/wiki/Special:BookSources/952-5216-18-7). 1. **[^](#cite_ref-3)** Parris, N (2002). ["Recyclable zein-coated kraft paper and linerboard"](https://web.archive.org/web/20211104172056/https://www.fpl.fs.fed.us/documnts/pdf2002/parri02a.pdf) (PDF). *Progress in Paper Recycling*. **11** (3): 24–29. Archived from [the original](https://www.fpl.fs.fed.us/documnts/pdf2002/parri02a.pdf) (PDF) on 2021-11-04. Retrieved 4 November 2019. 1. **[^](#cite_ref-4)** ["The Southern Pines"](https://web.archive.org/web/20070709235422/http://www.fpl.fs.fed.us/documnts/usda/amwood/256spine.pdf) (PDF). US Department of Agriculture. 1985. Archived from [the original](http://www.fpl.fs.fed.us/documnts/usda/amwood/256spine.pdf) (PDF) on 2007-07-09. Retrieved 2007-09-13. 1. **[^](#cite_ref-5)** John, Anton. ["Hardwood grades explained"](https://www.reallycheapfloors.com/blog/hardwood-lumber-grades-101-oak-natural-grades-explained/). Retrieved 26 October 2022. 1. **[^](#cite_ref-6)** ["Kraft Paper Bags | Kraft Bags | BBCB"](https://bigbrowncarrierbag.co.uk/collections/kraft-paper-bags). *Big Brown Carrier Bag*. Retrieved 2025-11-07. 1. **[^](#cite_ref-7)** ["Collection Level"](https://chinapreservationtutorial.library.cornell.edu/content/collection-level/). *Library Preservation and Conservation Tutorial*. Cornell University Library. [Archived](https://web.archive.org/web/20240420005244/https://chinapreservationtutorial.library.cornell.edu/content/collection-level/) from the original on 2024-04-20. Retrieved 2026-01-22. The backbone is lined with kraft or wrapping paper. - Yam, K. L., *Encyclopedia of Packaging Technology*, John Wiley & Sons, 2009, [ISBN](/source/ISBN_(identifier)) [978-0-470-08704-6](https://en.wikipedia.org/wiki/Special:BookSources/978-0-470-08704-6) ## External links - Media related to [Kraft paper](https://commons.wikimedia.org/wiki/Category:Kraft_paper) at Wikimedia Commons v t e Paper Paper engineering / Papermaking History Paper Ancestors Bamboo and wooden slips Barkcloth Amate Tapa Birch bark Palm leaf Papyrus Parchment Vellum Developers Cai Lun Damjing Matthias Koops Friedrich Gottlob Keller Charles Fenerty Scholars Timothy Barrett Thomas Francis Carter Dard Hunter Tsien Tsuen-hsuin Types of paper By Plant Fiber Banana Manila hemp Cotton Dung Dó Hemp Lokta Mulberry Daluang Hanji Saa Samarkand Washi Pith (Rice) Pulpwood Rag India Mummy Xuan Stone by Process Acidic Acid-free Air-laid Blue Cardboard Cardstock Corrugated fiberboard Paperboard Bristol Crêpe Glassine Kraft Laid Ingres Onionskin Paper towel Seed Tissue Toilet Wasli Wood-free Wove Coated Asphalt Photographic Rosin Tar Thermal Wax by Use Bible Blotting Bond Butcher Construction Display Cartridge Contact Copy Carbonless Correction Electrical insulation Filteration Inkjet Newsprint Origami Parchment Rolling Ruled paper Genkō yōshi Graph Security Tracing Transfer Wallpaper Writing Materials Kaolinite (China clay) Fiber crop Paper chemicals Wood pulp Specifications Density Grammage Paper sizes Surface chemistry of paper Units of paper quantity Wet strength Manufacture and process Paper machine Calender Conical refiner Hollander beater Paper recycling Deinking Pulp bleaching Chlorine-free Pulping Kraft Organosolv Soda Sulfite Paper industry Environmental impact of paper Paper industry Canada Europe India Indonesia Japan United States Paper mill List Uses Blueprint Papier-mâché Clothing Watercolor paper Paper money Category Commons --- Adapted from the Wikipedia article [Kraft paper](https://en.wikipedia.org/wiki/Kraft_paper) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Kraft_paper?action=history)). 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