Editing Shellac (section)

== 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=Yacoubou2010>{{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=Velji2010At5m23s>{{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=Berenbaum1993Page27>{{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}}