View source for Shellac

{{Short description|Resin secreted by the female lac bug}}
{{For|the rock band|Shellac (band)}}
{{Use dmy dates|date=September 2019}}
[[File:Shellac varities.png|right|thumb|upright=1.4|Some of the many different colors of shellac]]
[[File:Shellac liquid (cropped).jpeg|thumb|right|Shellac in alcohol]]

'''Shellac''' ({{IPAc-en|ʃ|ə|ˈ|l|æ|k}})<ref>{{cite web |url=https://dictionary.cambridge.org/dictionary/english/shellac |work=Cambridge Dictionary |access-date=19 October 2020 |title=Shellac }}</ref> is a [[resin]] secreted by the female [[Kerria lacca|lac bug]] on trees in the forests of India and Thailand. Chemically, it is mainly composed of [[aleuritic acid]], jalaric acid, shellolic acid, and other natural waxes.<ref>{{Cite journal |last1=Irimia-Vladu |first1=Mihai |last2=Głowacki |first2=Eric Daniel |last3=Schwabegger |first3=Günther |last4=Leonat |first4=Lucia |last5=Akpinar |first5=Hava Zekiye |last6=Sitter |first6=Helmut |last7=Bauer |first7=Siegfried |last8=Sariciftci |first8=Niyazi Serdar |date=2013 |title=Natural resin shellac as a substrate and a dielectric layer for organic field-effect transistors |url=https://xlink.rsc.org/?DOI=c3gc40388b |journal=Green Chemistry |language=en |volume=15 |issue=6 |pages=1473 |doi=10.1039/c3gc40388b |issn=1463-9262|url-access=subscription }}</ref> It is processed and sold as dry flakes and dissolved in [[ethanol|alcohol]] to make liquid shellac, which is used as a brush-on colorant, food [[glazing agent|glaze]] and [[wood finish]]. Shellac functions as a tough natural [[primer (paint)|primer]], [[sanding]] [[sealant]], [[tannin]]-blocker, [[odor]]-blocker, [[wood stain|stain]], and [[Gloss (material appearance)|high-gloss]] [[varnish]]. Shellac was once used in electrical applications as it is a good [[electrical insulation|insulator]] and seals out moisture. [[Phonograph]] and 78&nbsp;rpm [[gramophone record]]s were made of shellac until it was replaced by [[polyvinyl chloride|vinyl]].

From the time shellac replaced oil and wax finishes in the 19th century, it was one of the dominant wood finishes in the western world until it was largely replaced by [[nitrocellulose lacquer]] in the 1920s and 1930s. Besides wood finishing, shellac is used as an ingredient in food, medication and candy as ''[[resinous glaze|confectioner's glaze]]'',<ref>{{cite news |title=The Strange Ingredient Used To Make Jelly Beans Shiny |url=https://www.tastingtable.com/1041516/the-strange-ingredient-used-to-make-jelly-beans-shiny/ |work=TastingTable |last=Lee |first=John |publisher=Static Media}}</ref> and to preserve harvested [[citrus fruit]].<ref> {{cite journal |title=Shellac Formulations To Reduce Epiphytic Survival of Coliform Bacteria on Citrus Fruit Postharvest |journal=Journal of Food Protection |first1=Raymond G. |last1=Mcguire |first2=Robert D. |last2=Hagenmaier |doi=10.4315/0362-028X-64.11.1756 |volume=64 |issue=11 |date=1 November 2001 |pages=1756–1760|pmid=11726155 |doi-access=free }}</ref>

== Etymology ==
''Shellac'' comes from ''shell'' and ''[[Lac (resin)|lac]]'', a [[partial calque]] of [[French language|French]] {{lang|fr|laque en écailles}}, 'lac in thin pieces', later {{lang|fr|gomme-laque}}, 'gum lac'.<ref>{{cite web |url=http://www.etymonline.com/index.php?term=shellac |title=shellac |website=[[Online Etymology Dictionary]] |access-date=17 March 2015}}</ref> Most European languages (except [[Romance languages|Romance]] ones and Greek) have borrowed the word for the substance from English or from the [[German language|German]] equivalent {{lang|de|Schellack}}.<ref>{{Cite book|last=Smith|first=Peter|date=2016-12-15|chapter=§4. The Indo-European Family of Languages|url=https://pressbooks.bccampus.ca/greeklatinroots/chapter/4-indoeuropean-family-languages/|title=Greek and Latin Roots: Part I – Latin |publisher=University of Victoria|language=en-ca}}</ref>

== Production ==
{{see also|Lac (resin)}}
[[File:Kerria-lacca.jpg|thumb|Lac tubes created by ''Kerria lacca'']]
[[File:02-Indian-Insect-Life - Harold Maxwell-Lefroy - Kerria-Lacca.jpg|thumb|Drawing of the insect ''[[Kerria lacca]]'' and its shellac tubes, by [[Harold Maxwell-Lefroy]], 1909]]
Shellac is scraped from the [[Bark (botany)|bark]] of the trees where the female lac bug, ''[[Kerria lacca]]'' (order Hemiptera, family [[Kerriidae]], also known as ''Laccifer lacca''), secretes it to form a tunnel-like tube as it traverses the branches of the tree. Though these tunnels are sometimes referred to as "[[Cocoon (silk)|cocoons]]", they are not cocoons in the entomological sense.<ref>{{Cite journal |title=Coating and Taste Masking with Shellac |journal=Pharmaceutical Technology |url=https://www.pharmtech.com/view/coating-and-taste-masking-shellac |last1=Schad |first1=Beverly |date=2013-09-01 |issue=5 |volume=2013 |last2=Smith |first2=Houston |last3=Cheng |first3=Brian |last4=Scholten |first4=Jeff |last5=VanNess |first5=Eric |last6=Riley |first6=Tom}}</ref> This insect is in the same [[Superfamily (zoology)|superfamily]] as the insect from which [[cochineal#Dye|cochineal]] is obtained. The insects suck the sap of the tree and excrete "[[Lac (resin)|sticklac]]" almost constantly. The least-coloured shellac is produced when the insects feed on the kusum tree (''[[Schleichera]]'').<ref>{{Cite book |title=Processing Chemistry and Applications of Lac |last1=Baboo |first1=B. |publisher=Indian Council of Agricultural Research |year=2010 |pages=76 |url=https://archive.org/details/processingchemis00unse/page/74/mode/2up |last2=Goswami |first2=D. N. |quote=The resin obtained from Schleichera oleosa was superior to other resins in regard to some industrially important parameters e.g., flow (highest), heat polymerization time (longest) and colour index (lowest).}}</ref>

The number of lac bugs required to produce {{convert|1|kg|1}} of shellac has variously been estimated between {{formatnum:50000}} and  {{formatnum:300000}}.<ref name="Yacoubou-2010">{{cite web|last1=Yacoubou|first1=Jeanne|title=Q & A on Shellac|url=http://www.vrg.org/blog/2010/11/30/q-a-on-shellac/|website=Vegetarian Resource Group|access-date=3 July 2014|date=30 November 2010}}</ref><ref name="Velji-2010">{{cite web|last1=Velji|first1=Vijay|title=Shellac Origins and Manufacture|url=https://www.youtube.com/watch?v=lQcQ0yuekZ0&t=5m23s| archive-url=https://ghostarchive.org/varchive/youtube/20211211/lQcQ0yuekZ0| archive-date=2021-12-11 | url-status=live|publisher=shellacfinishes.com|access-date=3 July 2014|year=2010}}{{cbignore}}</ref> The root word [[lakh]] is a unit in the [[Indian numbering system]] for {{formatnum:100000}} and presumably refers to the huge numbers of insects that swarm on host trees, up to {{convert|150|/in2}}.<ref name="Berenbaum-1993">{{cite book|last1=Berenbaum|first1=May|title=Ninety-nine More Maggots, Mites, and Munchers|url=https://archive.org/details/ninetyninemorema00bere|url-access=registration|date=1993|publisher=University of Illinois Press|isbn=978-0-252-02016-2|page=[https://archive.org/details/ninetyninemorema00bere/page/27 27]}}</ref>

The raw shellac, which contains bark shavings and lac bugs removed during scraping, is placed in canvas tubes (much like long socks) and heated over a fire. This causes the shellac to liquefy, and it seeps out of the canvas, leaving the bark and bugs behind. The thick, sticky shellac is then dried into a flat sheet and broken into flakes, or dried into "buttons" (pucks/cakes), then bagged and sold. The end-user then crushes it into a fine powder and mixes it with [[ethyl alcohol]] before use, to dissolve the flakes and make liquid shellac.<ref>{{Cite web|title=How and why to mix fresh shellac|url=https://www.stewmac.com/video-and-ideas/online-resources/learn-about-instrument-finishing-and-finish-repair/how-and-why-to-mix-fresh-shellac/|access-date=2021-10-13|website=www.stewmac.com|language=en}}</ref>

Liquid shellac has a limited shelf life (about 1 year), so is sold in dry form for dissolution before use. Liquid shellac sold in hardware stores is often marked with the production (mixing) date, so the consumer can know whether the shellac inside is still good. Some manufacturers (e.g., Zinsser) have ceased labeling shellac with the production date, but the production date may be discernible from the production lot code. Alternatively, old shellac may be tested to see if it is still usable: a few drops on glass should dry to a hard surface in roughly 15 minutes. Shellac that remains tacky for a long time is no longer usable. Storage life depends on peak temperature, so refrigeration extends shelf life.<ref>{{cite web |title=Shellac |url=https://www.cargohandbook.com/Shellac |website=Cargo Handbook |access-date=14 May 2025}}</ref>

The thickness (concentration) of shellac is measured by the unit "pound cut", referring to the amount (in pounds) of shellac flakes dissolved in a gallon of denatured alcohol. For example: a 1-lb. cut of shellac is the strength obtained by dissolving one pound of shellac flakes in a gallon of alcohol (equivalent to {{convert|1|lb/USgal|g/L|abbr=off|disp=out}}).<ref>{{cite web |url=https://www.shellac.net/PoundCutChart.html |title= Dissolving & Mixing Shellac Flakes: Shellac 'Pound Cut' Chart |website=shellac.net |access-date=19 October 2020 }}</ref> Most pre-mixed commercial preparations come at a 3-lb. cut. Multiple thin layers of shellac produce a significantly better end result than a few thick layers. Thick layers of shellac do not adhere to the substrate or to each other well, and thus can peel off with relative ease; in addition, thick shellac will obscure fine details in carved designs in wood and other substrates.{{Cn|date=January 2021}}

Shellac naturally dries to a high-gloss sheen. For applications where a flatter (less shiny) sheen is desired, products containing amorphous silica, such as "Shellac Flat", may be added to the dissolved shellac.<ref>{{Cite web |url=http://americanwoodworker.com/blogs/shop/archive/2009/07/02/shellac.aspx |title=American Woodworker: Tips for Using Shellac |access-date=26 January 2010 |archive-date=10 November 2011 |archive-url=https://web.archive.org/web/20111110082356/http://americanwoodworker.com/blogs/shop/archive/2009/07/02/shellac.aspx |url-status=dead }}</ref>

Shellac naturally contains a small amount of wax (3%–5% by volume), which comes from the lac bug. In some preparations, this wax is removed (the resulting product being called "dewaxed shellac"). This is done for applications where the shellac will be coated with something else (such as paint or varnish), so the topcoat will adhere. Waxy (non-dewaxed) shellac appears milky in liquid form, but dries clear.{{Cn|date=January 2021}}

== Colours and availability ==
Shellac comes in many warm colours, ranging from a very light blonde ("platina") to a very dark brown ("garnet"), with many varieties of brown, yellow, orange and red in between. The colour is influenced by the sap of the tree the lac bug is living on and by the time of harvest. Historically, the most commonly sold shellac is called "orange shellac", and was used extensively as a combination stain and protectant for wood panelling and [[cabinetry]] in the 20th century.{{Cn|date=January 2021}}

Shellac was once very common anywhere paints or varnishes were sold (such as hardware stores). However, cheaper and more abrasion- and chemical-resistant finishes, such as [[polyurethane]], have almost completely replaced it in decorative residential wood finishing such as hardwood floors, wooden [[wainscoting]] plank panelling, and kitchen cabinets.  These alternative products, however, must be applied over a stain if the user wants the wood to be coloured; clear or blonde shellac may be applied over a stain without affecting the colour of the finished piece, as a protective topcoat. "Wax over shellac" (an application of buffed-on paste wax over several coats of shellac) is often regarded as a beautiful, if fragile, finish for hardwood floors. [[Luthier]]s still use shellac to ''[[French polish]]'' fine acoustic stringed instruments, but it has been replaced by synthetic plastic lacquers and varnishes in many workshops, especially high-volume production environments.<ref>[http://www.milburnguitars.com/fpbannerframes.html French polishing tutorial for guitars]</ref>

Shellac dissolved in alcohol, typically more dilute than as used in French polish, is now commonly sold as "sanding sealer" by several companies. It is used to seal wooden surfaces, often as preparation for a final more durable finish; it reduces the amount of final coating required by reducing its absorption into the wood.{{Cn|date=January 2021}}

== Properties ==
[[File:Haydn shellac.jpg|thumb|right|A decorative medal made in France in the early 20th century moulded from shellac compound, the same used for [[phonograph record]]s of the period]]
Shellac is a natural [[bioadhesive]] [[polymer]] and is chemically similar to synthetic polymers.<ref>https://pubchem.ncbi.nlm.nih.gov/compound/shellac gives the chief component as 9,10,15-trihydroxypentadecanoic acid and also (2R,6S,7R,10S)-10-hydroxy-6-(hydroxymethyl)-6-methyltricycloundec-8-ene-2,8-dicarboxylic acid, molecular formula C<sub>30</sub>H<sub>50</sub>O<sub>11</sub> with a molecular weight of 586.7 g/mol </ref> It can thus be considered a natural form of [[plastic]].
 
With a melting point of {{convert|75|C}}, it can be classed as a [[thermoplastic]] used to bind [[wood flour]], the mixture can be [[moulding (process)|moulded]] with heat and pressure.

Shellac scratches more easily than most lacquers and varnishes, and application is more labour-intensive, which is why it has been replaced by plastic in most areas.  Shellac is much softer than [[Urushi]] lacquer, for instance, which is far superior with regard to both chemical and mechanical resistance.{{Cn|date=January 2021}} But damaged shellac can easily be touched up with another coat of shellac (unlike polyurethane, which chemically cures to a solid) because the new coat merges with and bonds to the existing coat(s).

Shellac is [[solubility|soluble]] in [[alkaline]] solutions of [[ammonia]], [[sodium borate]], [[sodium carbonate]], and [[sodium hydroxide]], and also in various [[organic solvent]]s. When dissolved in alcohol (typically [[Denatured alcohol|denatured ethanol]]) for application, shellac yields a coating of good durability and hardness.<ref>{{Cite journal |last1=Chen |first1=Ying |last2=Zhu |first2=Zhu |last3=Shi |first3=Kunbo |last4=Jiang |first4=Zhiyao |last5=Guan |first5=Chengran |last6=Zhang |first6=Liang |last7=Yang |first7=Tao |last8=Xie |first8=Fengwei |date=2024-11-01 |title=Shellac-based materials: Structures, properties, and applications |journal=International Journal of Biological Macromolecules |volume=279 |issue=Pt 1 |article-number=135102 |doi=10.1016/j.ijbiomac.2024.135102 |pmid=39197605 |issn=0141-8130|doi-access=free }}</ref>

Upon mild [[hydrolysis]] shellac gives a complex mix of [[aliphatic]] and [[alicyclic]] [[hydroxy acids]] and their polymers that varies in exact composition depending upon the source of the shellac and the season of collection. The major component of the aliphatic component is [[aleuritic acid]], whereas the main alicyclic component is [[shellolic acid]].<ref name="Merck Index">Merck Index, 9th Ed. page 8224.</ref>

Shellac is UV-resistant, and does not darken as it ages (though the wood under it may do so, as in the case of pine).<ref name="Naturalhandyman" />

== History ==
[[File:Laksha - ලාක්ෂා - Lacquerware.jpg|thumb|right|''Laksha'' is a traditional form of lacquerware from Sri Lanka which is made from shellac derived from [[Lac (resin)|Lac]] resin.]]
The earliest written evidence of shellac goes back {{formatnum:3000}} years, but shellac is known to have been used earlier.<ref name="Naturalhandyman">[https://www.naturalhandyman.com/iip/infpai/shellac.html Naturalhandyman.com : DEFEND, PRESERVE, AND PROTECT WITH SHELLAC : The Story of Shellac]</ref> According to the ancient Indian epic poem, the [[Mahabharata]], an entire palace was coated with dried shellac.<ref name="Naturalhandyman" />

Shellac was uncommonly used as a dyestuff for as long as there was a trade with the [[East Indies]]. According to Merrifield,<ref name="Merrifield-1849">{{cite book
 |year=1849
 |title=Original Treatises on the Art of Painting
 |last=Merrifield |first=Mary
 |isbn=978-0-486-40440-0
 |publisher=Dover Publ.
 |location=Mineola, N.Y.
}}</ref> shellac was first used as a binding agent in artist's pigments in Spain in the year 1220. 

The use of overall paint or varnish decoration on large pieces of furniture was first popularised in Venice (then later throughout Italy). There are a number of 13th-century references to painted or varnished [[cassone]], often [[dowry]] cassone that were made deliberately impressive as part of dynastic marriages. The definition of varnish is not always clear, but it seems to have been a [[Varnish#Shellac|spirit varnish]] based on [[Benzoin resin|gum benjamin]] or [[Mastic (plant resin)|mastic]], both traded around the Mediterranean. At some time, shellac began to be used as well. An article from the ''Journal of the American Institute of Conservation'' describes using [[infrared spectroscopy]] to identify shellac coating on a 16th-century cassone.<ref name="Derrick-1992">{{cite journal
 |title=Furniture finish layer identification by infrared linear mapping microspectroscopy
 |url=http://aic.stanford.edu/jaic/articles/jaic31-02-006.html
 |journal=Journal of the American Institute of Conservation
 |volume=31
 |issue=2, Article 6
 |pages=225 to 236
 |year=1992
 |doi=10.2307/3179494
 |jstor=3179494
 |last1=Derrick
 |first1=Michele R.
 |last2=Stulik
 |first2=Dusan C.
 |last3=Landry
 |first3=James M.
 |last4=Bouffard
 |first4=Steven P.
 |access-date=16 May 2008
 |archive-date=6 July 2009
 |archive-url=https://web.archive.org/web/20090706072547/http://aic.stanford.edu/jaic/articles/jaic31-02-006.html
 |url-status=dead
 |url-access=subscription
 }}</ref> This is also the period in history where "varnisher" was identified as a distinct trade, separate from both carpenter and artist.{{Cn|date=January 2021}}

Another use for shellac is [[sealing wax]].<ref name="Woods-1994">{{cite journal
 |title=The Nature and Treatment of Wax and Shellac Seals
 |last=Woods |first=C.
 |year=1994
 |issue=2
 |pages=203–214 |journal=Journal of the Society of Archivists
|volume=15 |doi=10.1080/00379819409511747 }}</ref> The widespread use of shellac seals in Europe dates back to the [[17th century]], thanks to the increasing trade with India.<ref>{{Cite journal |title=Some Notes on the Preservation, Moulding and Casting of Seals |journal=The Antiquaries Journal |last=Jenkinson |first=Hilary |date=1924-05-22 |issue=4 |volume=4 |pages=388–403 |doi=10.1017/S0003581500006193|s2cid=137543748 }}</ref>

== Uses ==
=== Historical ===
In the early- and mid-twentieth century, orange shellac was used as a one-product finish (combination stain and varnish-like topcoat) on decorative wood panelling used on walls and ceilings in homes, particularly in the US. In the [[American South]], use of knotty [[pine]] plank [[panelling]] covered with orange shellac was once as common in new construction as [[drywall]] is today. It was also often used on kitchen cabinets and hardwood floors, prior to the advent of [[polyurethane]].{{Cn|date=January 2021}}

Until the advent of [[Polyvinyl chloride|vinyl]], most [[gramophone records]] were pressed from shellac compounds.<ref>{{cite journal|last1=Rheding|first1=Alexander|title=On the Record|journal=Cambridge Opera Journal|date=2006|volume=18|issue=1|pages=59–82|doi=10.1017/S0954586706002102|s2cid=231810582}}</ref><ref>{{cite journal|last1=Melillo|first1=Edward|title=Global Entomologies: Insects, Empires, and the 'Synthetic Age' in World History|journal=Past & Present|date=2014|issue=223|pages=233–270|url=https://academic.oup.com/past/article-abstract/223/1/233/1426060|doi=10.1093/pastj/gtt026|url-access=subscription}}</ref> From 1921 to 1928, {{formatnum:18000}} tons of shellac were used to create 260 million records for Europe.<ref name="Berenbaum-1993" /> In the 1930s, it was estimated that half of all shellac was used for [[Phonograph record|gramophone records]].<ref name="The Mall-1937">{{cite news|title=How Shellac Is Manufactured|url=http://nla.gov.au/nla.news-article55073762|access-date=3 July 2014|publisher=The Mail (Adelaide, SA : 1912–1954)|date=18 December 1937}}</ref> Use of shellac for records was common until the 1950s and continued into the 1970s in some non-Western countries, as well as for some children's records.<ref>{{Cite web |date=2020-12-28 |title=My Turntable Has 3 Speeds But Are 78 RPM Records Still Made? {{!}} Vinyl Bro {{!}} Elevate Your Music |url=https://vinylbro.com/are-78-rpm-records-still-made/ |access-date=2022-12-30 |language=en-us}}</ref><ref>{{Cite web |title=The history of 78 RPM recordings {{!}} Yale University Library |url=https://web.library.yale.edu/cataloging/music/historyof78rpms |access-date=2022-12-30 |website=web.library.yale.edu}}</ref>

Until recent advances in technology, shellac was the only glue used in the making of [[ballet]] dancers' [[pointe shoe]]s, to stiffen the box (toe area) to support the dancer en pointe. Many manufacturers of pointe shoes still use the traditional techniques, and many dancers use shellac to revive a softening pair of shoes.<ref>{{Cite web
| url = http://www.bloch.com.au/content/54-maintenance-of-pointe-shoes
| title = Maintenance of Pointe Shoes – Bloch Australia
| website = Bloch Australia
| access-date = 17 March 2016
| archive-date = 18 April 2019
| archive-url = https://web.archive.org/web/20190418021244/https://www.bloch.com.au/content/54-maintenance-of-pointe-shoes
| url-status = dead
}}</ref>

Shellac was historically used as a protective coating on paintings.{{Cn|date=January 2021}}

Sheets of [[Braille]] were coated with shellac to help protect them from [[wear]] due to being read by hand.{{Cn|date=January 2021}}

Shellac was used from the mid-nineteenth century to produce small moulded goods such as [[picture frame]]s, [[box]]es, toilet articles, [[jewelry]], [[inkwell]]s and even [[dentures]]. Advances in [[plastics]] have rendered shellac obsolete as a moulding compound.<ref>{{Cite web |last=Freinkel |first=Susan |title=A Brief History of Plastic's Conquest of the World |url=https://www.scientificamerican.com/article/a-brief-history-of-plastic-world-conquest/ |access-date=2022-04-21 |website=Scientific American |language=en}}</ref>

Shellac (both orange and white varieties) was used both in the field and laboratory to glue and stabilise dinosaur bones until about the mid-1960s. While effective at the time, the long-term negative effects of shellac (being organic in nature) on dinosaur bones and other fossils is debated, and shellac is very rarely used by professional conservators and fossil preparators today.<ref>{{Cite web |title=PaleoPortal Fossil Preparation {{!}} Tips |url=http://preparation.paleo.amnh.org/50/tips |access-date=2023-05-06 |website=preparation.paleo.amnh.org}}</ref>

Shellac was used for fixing [[inductor]], [[Electric motor|motor]], [[Electrical generator|generator]] and [[transformer]] windings. It was applied directly to single-layer windings in an alcohol solution. For multi-layer windings, the whole coil was submerged in shellac solution, then drained and placed in a warm location to allow the alcohol to evaporate. The shellac locked the wire turns in place, provided extra insulation, prevented movement and vibration and reduced buzz and hum. In motors and generators it also helps transfer force generated by magnetic attraction and repulsion from the windings to the rotor or [[armature (electrical engineering)|armature]]. In more recent times, shellac has been replaced in these applications by synthetic resins such as [[polyester resin]]. Some applications use shellac mixed with other natural or synthetic resins, such as [[pine resin]] or phenol-[[formaldehyde]] resin, of which [[Bakelite]] is the best known, for electrical use. Mixed with other resins, [[barium sulfate]], [[calcium carbonate]], [[zinc sulfide]], [[aluminium oxide]] and/or cuprous carbonate ([[malachite]]), shellac forms a component of heat-cured capping cement used to fasten the caps or bases to the bulbs of electric lamps.{{Cn|date=January 2021}}

=== Current uses ===
It is the central element of the traditional "[[French polish]]" method of [[wood finishing|finishing]] furniture, fine [[string instrument]]s, and [[piano]]s.<ref>{{cite book |last1=Bitmead |first1=Richard |title=French Polishing and Enamelling |date=1910 |publisher=Crosby Lockwood and Son |location=London |pages=Preface, 18 ff |edition=4 |url=https://www.gutenberg.org/files/17935/17935-h/17935-h.htm |access-date=26 June 2021}}</ref>

Shellac, being edible, is used as a [[glazing agent]] on pills (see [[excipient]]) and sweets, in the form of [[pharmaceutical glaze]] (or, "confectioner's glaze"). Because of its acidic properties (resisting stomach acids), shellac-coated pills may be used for a timed [[Enteric coating|enteric]] or colonic release.<ref>[http://www.patentstorm.us/patents/6620431.html Shellac film coatings providing release at selected pH and method – US Patent 6620431] {{webarchive|url=https://web.archive.org/web/20070929083616/http://www.patentstorm.us/patents/6620431.html |date=29 September 2007 }}</ref> Shellac is used as a 'wax' coating on citrus fruit to prolong its shelf/storage life. It is also used to replace the natural wax of the [[apple]], which is removed during the cleaning process.<ref>{{cite web |url=http://usapple.org/consumers/wax.cfm |title=US Apple: Consumers – FAQs: Apples and Wax |access-date=2012-02-03 |url-status=dead |archive-url=https://web.archive.org/web/20101203123752/http://usapple.org/consumers/wax.cfm |archive-date=3 December 2010 |df=dmy-all }}</ref> When used for this purpose, it has the [[food additive]] [[E number]] E904.<ref>{{cite web |title=Bleached Shellac |url=https://shellacthailand.com/en/product-and-services/bleached-shellac/ |publisher=Creasia Group |access-date=19 October 2022}}</ref>

Shellac is an odour and stain blocker and so is often used as the base of "all-purpose" primers. Although its durability against abrasives and many common solvents is not very good, shellac provides an excellent barrier against water vapour penetration. Shellac-based primers are an effective sealant to control odours associated with fire damage.<ref>{{cite web |last1=Stanton |first1=Cole |title=Solutions by Sixes and Sevens: Smoke Sealers during Smoke Odor & Fire Damage Restoration |url=https://www.randrmagonline.com/articles/87371-solutions-by-sixes-and-sevens-smoke-sealers-during-smoke-odor-fire-damage-restoration |website=Restoration & Remediation Magazine |access-date=13 December 2023}}</ref>

Shellac has traditionally been used as a dye for cotton and, especially, silk cloth in Thailand, particularly in the north-eastern region.<ref name="Suanmuang-1999">Suanmuang Tulaphan, Phunsap, ''Silk Dyeing With Natural Dyestuffs in Northeastern Thailand'', 1999, p. 26-30 (in Thai)</ref> It yields a range of warm colours from pale yellow through to dark orange-reds and dark ochre.<ref name="Punyaprasop-2001">Punyaprasop, Daranee (Ed.)Colour ''And Pattern On Native Cloth'', 2001, p. 253, 256 (in Thai)</ref> Naturally dyed silk cloth, including that using shellac, is widely available in the rural northeast, especially in [[Ban Khwao District]], [[Chaiyaphum province]]. The Thai name for the insect and the substance is "khrang" (Thai: ครั่ง).{{Cn|date=January 2021}}

====Wood finish====

Wood finishing is one of the most traditional and still popular uses of shellac mixed with solvents or alcohol. This dissolved shellac liquid, applied to a piece of wood, is an evaporative finish: the alcohol of the shellac mixture evaporates, leaving behind a protective film.<ref>{{Cite book|title=Woodworking Tools and Techniques: An Introduction to Basic Woodworking|last=Marshall|first=Chris|publisher=Creative Publishing International, US|year=2004|pages=137}}</ref>

Shellac as wood finish is natural and non-toxic in its pure form. A finish made of shellac is UV-resistant. For water-resistance and durability, it does not keep up with synthetic finishing products.<ref>{{Cite web|url=https://thediyhammer.com/shellac-vs-polyurethane-vs-varnish-wood-finishing-faqs/|title=Wood Finishing FAQs: Shellac vs. Polyurethane vs. Varnish|website=TheDIYhammer|date=31 July 2019|access-date=4 August 2019}}</ref>

Because it is compatible with most other finishes, shellac is also used as a barrier or primer coat on [[wood]] to prevent the bleeding of [[resin]] or [[pigments]] into the final finish, or to prevent [[wood stain]] from blotching.<ref name="Shellac">Shellac, [http://www.woodworkdetails.com/knowledge/finishing/shellac WoodworkDetails.com: Shellac as a Woodworking Finish]{{Circular reference|date=March 2015}}</ref>

==== Other ====
Shellac is used:
* in the tying of artificial flies for trout and salmon, where the shellac was used to seal all trimmed materials at the head of the fly.{{Cn|date=January 2021}}
* in combination with wax for preserving and imparting a shine to [[Citrus|citrus fruits]], such as [[lemon]]s and [[Orange (fruit)|orange]]s.<ref>{{Cite web |url=https://www.independent.co.uk/life-style/food-and-drink/vegans-fruit-unsuitable-wax-diet-b2149877.html |title=Why not all fruit is suitable for vegans |date=2022-08-22 |access-date=2023-12-21 |website=The Independent |last=Sommerlad |first=Joe}}</ref><ref>{{Cite journal |title=Shellac, gelatin and Persian gum as alternative coating for orange fruit |journal=Scientia Horticulturae |url=https://www.sciencedirect.com/science/article/abs/pii/S0304423817303849 |last1=Khorram |first1=Fereshteh |date=2017-11-18 |volume=225 |pages=22–28 |last2=Ramezanian |first2=Asghar |doi=10.1016/j.scienta.2017.06.045 |last3=Hosseini |first3=Seyyed Mohammad Hashem|bibcode=2017ScHor.225...22K |url-access=subscription }}</ref>
* in [[dentistry|dental technology]], where it is occasionally used in the production of custom impression trays and temporary denture baseplate production.<ref>{{Cite journal |title=The production of shellac and its general and dental uses: a review |journal=Journal of Oral Rehabilitation |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2842.1993.tb01623.x#:~:text=In%20its%20refined%20form%2C%20shellac,rims%20when%20recording%20jaw%20relationships. |last1=Azouka |first1=A. |issue=4 |volume=20 |pages=393–400 |last2=Huggett |first2=R. |doi=10.1111/j.1365-2842.1993.tb01623.x |year=1993 |last3=Harrison |first3=A.|pmid=8350174 |url-access=subscription }}</ref>
* as a binder in [[India ink]].<ref>{{cite web |title=Ink |url=https://www.moma.org/collection/terms/ink |website=MoMA |access-date=17 October 2021}}</ref>
* for [[bicycles]], as a protective and decorative coating for [[bicycle handlebar]] tape,<ref>{{Cite web |url=http://www.outyourbackdoor.com/article.php?id=428 |title=Shellac & Twine makes Handlebar fine |date=21 August 2005 |website=Out Your Backdoor |access-date=17 March 2015}}</ref> and as a hard-drying adhesive for [[tubular tyres]], particularly for [[track cycling|track racing]].<ref>[http://www.sheldonbrown.com/brandt/mounting-tubulars.html Mounting Tubular Tires] by [[Jobst Brandt]]</ref>
* for re-attaching ink sacs when restoring vintage [[fountain pen]]s, the orange variety preferably.{{Cn|date=January 2021}}
* applied as a coating with either a standard or modified Huon-Stuehrer nozzle, can be economically micro-sprayed onto various smooth candies, such as chocolate coated peanuts. Irregularities on the surface of the product being sprayed may result in the formation of unsightly aggregates ("lac-aggs") which precludes the use of this technique on foods such as walnuts or raisins.
* for fixing pads to the key-cups of [[woodwind]] instruments.{{Cn|date=January 2021}}
* for [[luthier]]ie applications, to bind wood fibres down and prevent tear out on the soft [[spruce]] soundboards.{{Cn|date=January 2021}}
* to stiffen and impart water-resistance to felt hats, for wood finishing<ref>{{cite web |url=http://antiquerestorers.com/Articles/jeff/shellac.htm |title=Shellac: A traditional finish still yields superb results |last=Jewitt |first=Jeff |website=Antique Restorers |access-date=16 March 2015}}</ref> and as a constituent of ''gossamer'' (or ''goss'' for short), a cheesecloth fabric coated in shellac and [[ammonia]] solution used in the shell of traditional silk [[top hats|top]] and riding hats.
* for mounting insects, in the form of a gel adhesive mixture composed of 75% ethyl alcohol.<ref>[http://www.nadsdiptera.org/News/FlyTimes/issue18.htm Fly Times: Shellac gel for insect mounting]</ref>
* as a binder in the fabrication of [[abrasive wheel]]s,<ref>{{Cite book
 |title=Grinding Technology: Theory and Applications of Machining With Abrasives
 |author=Stephen Malkin |author2=Changsheng Guo
 |publisher=Industrial Press
 |year=2008
 |url=https://books.google.com/books?id=l3260ZF_PfQC&pg=PA5
 |page=5
|isbn=9780831132477 }}</ref> imparting flexibility and smoothness not found in vitrified (ceramic bond) wheels. 'Elastic' bonded wheels typically contain [[plaster of paris]], yielding a stronger bond when mixed with shellac; the mixture of dry plaster powder, abrasive (e.g. [[corundum]]/[[aluminium oxide]] Al<sub>2</sub>O<sub>3</sub>), and shellac are heated and the mixture pressed in a mould.
* in [[fireworks]] pyrotechnic compositions as a low-temperature fuel, where it allows the creation of pure 'greens' and 'blues'- colours difficult to achieve with other fuel mixes.{{Cn|date=January 2021}}
* in [[jewellery]]; shellac is often applied to the top of a 'shellac stick' in order to hold small, complex, objects. By melting the shellac, the jeweller can press the object (such as a stone setting mount) into it. The shellac, once cool, can firmly hold the object, allowing it to be manipulated with tools.<ref>{{Cite web|title=Stone Setting Tools FAQs |url=https://www.ganoksin.com/article/stone-setting-tools-faqs/|access-date=2022-01-25|website=Ganoksin|language=en}}</ref>
* in [[watchmaking]], due to its low melting temperature (about {{convert|80|-|100|C}}), shellac is used in most mechanical movements to adjust and adhere pallet stones to the [[pallet fork]] and secure the roller jewel to the roller table of the [[balance wheel]]. Also for securing small parts to a 'wax chuck' (faceplate) in a watchmakers' lathe.<ref>{{Cite web |title=Shellac |url=https://watchmakingjourney.com/tag/shellac/ |access-date=2022-07-12 |website=watchmaking journey |date=19 September 2014 |language=en}}</ref>
* in the early twentieth century, it was used to protect some military [[rifle]] stocks.<ref>{{cite web |url=http://www.russian-mosin-nagant.com/faq/#Q3 |title=What kind of finish is on my stock? |website=Russian Mosin Nagant Forum |access-date=21 March 2015}}</ref>
* in [[Jelly Belly]] jelly beans, in combination with [[beeswax]] to give them their final buff and polish.<ref>[http://www.jellybelly-uk.com/faq/q-and-a/?id=11 Q&A – Jelly Belly jelly beans] {{webarchive|url=https://web.archive.org/web/20140105045321/http://www.jellybelly-uk.com/faq/q-and-a/?id=11 |date=5 January 2014 }}</ref>
* in modern traditional [[archery]], shellac is one of the [[Hot-melt adhesive|hot-melt glue/resin]] products used to attach [[arrowhead]]s to wooden or bamboo [[arrow]] shafts.<ref>{{Cite book |last=Sapp |first=Rick |title=The Ultimate Guide to Traditional Archery |year=2013 |publisher=Simon and Schuster |isbn=9781626365360}}</ref><ref>{{cite web | url=https://www.metmuseum.org/art/collection/search/26595 | title=Part of a Quiver &#124; Tibetan or Mongolian |publisher=Metropolitan Museum of Art}}</ref>
* in alcohol solution as [[sanding sealer]], widely sold to seal sanded surfaces, typically wooden surfaces before a final coat of a more durable finish. Similar to French polish but more dilute.<ref>{{Cite web |last=Dezeil |first=Chris |title=What is a Sanding Sealer? |date=23 April 2009 |url=https://www.hunker.com/12170980/what-is-a-sanding-sealer }}</ref>
* as a topcoat in [[nail polish]] (although not all [[nail polish]] sold as "shellac" contains shellac, and some [[nail polish]] not labelled in this way does).{{Cn|date=January 2021}}
* in sculpture, to seal [[plaster]] and in conjunction with wax or oil-soaps, to act as a barrier during mold-making processes.{{Cn|date=January 2021}}
* as a dilute solution in the sealing of [[harpsichord]] soundboards, protecting them from dust and buffering humidity changes while maintaining a bare-wood appearance.{{Cn|date=January 2021}}
* as a waterproofing agent for leather (e.g., for the soles of [[figure skate]] boots).
* as a way for ballet dancers to harden their [[pointe shoes]], making them last longer.<ref>{{cite web | url=https://www.ballet.org.uk/blog-detail/a-guide-to-pointe-shoes/ | title=Everything you Need to Know About Pointe Shoes |publisher=English National Ballet}}</ref><ref>{{Cite web |last=Chang Foster |first=Hannah |title=Confessions of a Pointe Shoe Fitter: A Specialist Tells All |date=31 May 2016 |url=https://pointemagazine.com/pointe-shoe-fitting/ |publisher=Pointe Magazine}}</ref>

== Gallery ==
<gallery mode="packed">
File:Schellak.jpg|Blonde shellac flakes
File:Shellac.JPG|Dewaxed Bona (L) and Waxy #1 Orange (R) shellac flakes. The latter—orange shellac—is the traditional shellac used for decades to finish wooden wall paneling, kitchen cabinets and tool handles.
File:Shellac flakes closeup.JPG|Closeup of Waxy #1 Orange (L) and Dewaxed Bona (R) shellac flakes. The former—orange shellac—is the traditional shellac used for centuries to finish wooden wall paneling and kitchen cabinets.
File:Shellac board.JPG|"Quick and dirty" example of a pine board coated with 1–5 coats of Dewaxed Dark shellac (a darker version of traditional orange shellac)
</gallery>

== See also ==
* [[Polymer|Polymers]]
* [[Rosin]]

== References ==

{{Reflist|30em}}

== External links ==
{{Commons category|Shellac}}
{{Wiktionary|shellac}}
* [http://www.shellac.net/ Shellac.net] US shellac vendor – properties and uses of dewaxed and non-dewaxed shellac
* [http://www.naturalhandyman.com/iip/infpai/shellac.html The Story of Shellac (history)]
* [https://web.archive.org/web/20070515031424/http://www.diyinfo.org/wiki/All_About_Shellac DIYinfo.org's Shellac Wiki], practical information on everything to do with shellac
* Reactive Pyrolysis-Gas Chromatography of Shellac {{doi|10.1021/ac981049e}}
* [http://www.buildingconservation.com/articles/shellac/shellac.htm Shellac] A short introduction to the origin of shellac, the history of Japanning and French polishing, and how to conserve and repair these finishes sympathetically
* [http://www.frenchpolishes.com/application_information/shellac_polish_application.htm Shellac Application] By Smith & Rodger

{{E number infobox 900-909}}
{{Non-timber forest products}}
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[[Category:Wood finishing materials]]
[[Category:Food additives]]
[[Category:Insect products]]
[[Category:Polymers]]
[[Category:Resins]]
[[Category:Waxes]]
[[Category:Excipients]]
[[Category:Forestry in India]]
[[Category:Non-timber forest products]]
[[Category:E-number additives]]