SHELLAC RESIN

CAS Number :  9000-59-3
EC Number  :  232-549-9
Molecular Formula :  C30H50O11
Molecular Weight  :  586.7

Shellac resin is a resin secreted by the female lac bug on trees in the forests of India and Thailand. 
Shellac resin is processed and sold as dry flakes and dissolved in alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish. 
Shellac resin functions as a tough natural primer, sanding sealant, tannin-blocker, odour-blocker, stain, and high-gloss varnish. 
Shellac resin was once used in electrical applications as it possesses good insulation qualities and it seals out moisture. 
Phonograph and 78 rpm gramophone records were made of Shellac resin until they were replaced by vinyl long-playing records from 1948 onwards.

From the time Shellac resin replaced oil and wax finishes in the 19th century, shellac was one of the dominant wood finishes in the western world until it was largely replaced  by nitrocellulose lacquer in the 1920s and 1930s.

Etymology of Shellac resin
Shellac resin comes from shell and lac, a calque of French laque en écailles, 'lac in thin pieces', later gomme-laque, 'gum lac'.
Most European languages (except Romance ones and Greek) have borrowed the word for the substance from English or from the German equivalent Schellack.

Production of Shellac resin
Shellac resin is scraped from the 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 "cocoons", they are not cocoons in the entomological sense. 
This insect is in the same superfamily as the insect from which cochineal is obtained. 
The insects suck the sap of the tree and excrete "sticklac" almost constantly. 
The least-coloured Shellac resin is produced when the insects feed on the kusum tree (Schleichera).

The number of lac bugs required to produce 1 kilogram (2.2 lb) of Shellac resin has variously been estimated as 50,000, 200,000, or 300,000.
The root word lakh is a unit in Indian numbering system for 100,000 and presumably refers to the huge numbers of insects that swarm on host trees, up to 150 per square inch (23/cm2).

The raw Shellac resin, 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 resin to liquefy, and it seeps out of the canvas, leaving the bark and bugs behind. 
The thick, sticky Shellac resin 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 resin.

Liquid Shellac resin has a limited shelf life (about 1 year), so is sold in dry form for dissolution before use. 
Liquid Shellac resin 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 resin 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 resin that remains tacky for a long time is no longer usable. 
Storage life depends on peak temperature, so refrigeration extends shelf life.

The thickness (concentration) of Shellac resin 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 120 grams per litre).
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 resin 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.

Shellac resin 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.
Shellac resin 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.

Colours and availability of Shellac resin
Shellac resin 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 resin is called "orange shellac", and was used extensively as a combination stain and protectant for wood panelling and cabinetry in the 20th century.

Shellac resin 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. 
Luthiers 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.

Shellac resin dissolved in alcohol, typically more dilute than French-Polish, is now commonly sold as "sanding sealer" by several companies. 
Shellac resin is used to seal wooden surfaces, often as preparation for a final more durable finish; Shellac resin reduces the amount of final coating required by reducing its absorption into the wood.

Properties of Shellac resin
Shellac resin is a natural bioadhesive polymer and is chemically similar to synthetic polymers.
Shellac resin can thus can be considered a natural form of plastic.
With a melting point of 75 °C (167 °F), Shellac resin can be classed as a thermoplastic;used to bind wood flour, the mixture can be moulded with heat and pressure.

Shellac resin 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 resin is much softer than Urushi lacquer, for instance, which is far superior with regard to both chemical and mechanical resistance.
But damaged shellac can easily be touched up with another coat of Shellac resin (unlike polyurethane, which chemically cures to a solid) because the new coat merges with and bonds to the existing coat(s).

Shellac resin is soluble in alkaline solutions of ammonia, sodium borate, sodium carbonate, and sodium hydroxide, and also in various organic solvents. 
When dissolved in alcohol (typically denatured ethanol) for application, shellac yields a coating of good durability and hardness.
Upon mild hydrolysis Shellac resin 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.
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).

History of Shellac resin
The earliest written evidence of shellac goes back 3,000 years, but shellac is known to have been used earlier.
According to the ancient Indian epic poem, the Mahabharata, an entire palace was built out of dried shellac.
Shellac resin was in rare use as a dyestuff for as long as there was a trade with the East Indies. 
Merrifield cites 1220 for the introduction of shellac as an artist's pigment in Spain.

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 spirit varnish based on gum benjamin or mastic, both traded around the Mediterranean. 
At some time, Shellac resin 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.
This is also the period in history where "varnisher" was identified as a distinct trade, separate from both carpenter and artist.

Another use for shellac is sealing wax. 
Woods's The Nature and Treatment of Wax and Shellac Seals discusses the various formulations, and the period when shellac started to be added to the previous beeswax recipes.
The "period of widespread introduction" would seem to be around 1550 to 1650, when the substance moved from being a rarity on highly decorated pieces to being described in the standard texts of the day.

Uses of Shellac resin

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. 
Shellac resin was also often used on kitchen cabinets and hardwood floors, prior to the advent of polyurethane.

Until the advent of vinyl, most gramophone records were pressed from shellac compounds.
From 1921 to 1928, 18,000 tons of Shellac resin were used to create 260 million records for Europe.
In the 1930s, it was estimated that half of all shellac was used for gramophone records.
Use of shellac for records was common until the 1950s and continued into the 1970s in some non-Western countries.

Until recent advances in technology, Shellac resin (French polish) was the only glue used in the making of ballet dancers' pointe shoes, 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.
Shellac resin was historically used as a protective coating on paintings.
Sheets of Braille were coated with shellac to help protect them from wear due to being read by hand.

Shellac resin was used from the mid-nineteenth century to produce small moulded goods such as picture frames, boxes, toilet articles, jewelry, inkwells and even dentures. 
Advances in plastics have rendered shellac obsolete as a moulding compound.
Shellac resin (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.

Shellac resin was used for fixing inductor, motor, generator and transformer windings. 
Shellac resin 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 place 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. 

In more recent times, Shellac resin has been replaced in these applications by synthetic resins such as polyester resin. 
Some applications use Shellac resin 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.

Current
Shellac resin is the central element of the traditional "French polish" method of finishing furniture, fine string instruments, and pianos.
Shellac resin, 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 or colonic release.
Shellac resin is used as a 'wax' coating on citrus fruit to prolong its shelf/storage life. 
Shellac resin is also used to replace the natural wax of the apple, which is removed during the cleaning process.
When used for this purpose, Shellac resin has the food additive E number E904.

Shellac resin is an odour and stain blocker and so is often used as the base of "solves all problems" primers. 
Although its durability against abrasives and many common solvents is not very good, shellac provides an excellent barrier against water vapour penetration. 
Shellac resin-based primers are an effective sealant to control odours associated with fire damage.

Shellac resin has traditionally been used as a dye for cotton and, especially, silk cloth in Thailand, particularly in the north-eastern region.
Shellac resin yields a range of warm colours from pale yellow through to dark orange-reds and dark ochre.
Naturally dyed silk cloth, including that using Shellac resin, 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".

Wood finish
Wood finishing is one of the most traditional and still popular uses of shellac mixed with solvents or alcohol. 
This dissolved Shellac resin liquid, applied to a piece of wood, is an evaporative finish: the alcohol of the shellac mixture evaporates, leaving behind a protective film.

Shellac resin 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.
Because Shellac resin is compatible with most other finishes, Shellac resin 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.

Other
Shellac resin 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.
-in combination with wax for preserving and imparting a shine to citrus fruits, such as lemons.
-in dental technology, where it is occasionally used in the production of custom impression trays and (partial) denture production.
-as a binder in India ink.
-for bicycles, as a protective and decorative coating for bicycle handlebar tape, and as a hard-drying adhesive for tubular tyres, particularly for track racing.
-for re-attaching ink sacs when restoring vintage fountain pens, the orange variety preferably.
-Shellac coating applied 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.
-for Luthier applications, to bind wood fibres down and prevent tear out on the soft spruce soundboards.
-to stiffen and impart water-resistance to felt hats, for wood finishing 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 and riding hats.
-for mounting insects, in the form of a gel adhesive mixture composed of 75% ethyl alcohol.
-as a binder in the fabrication of abrasive wheels,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 Al2O3), 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.
-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 resin, once cool, can firmly hold the object - allowing it to be manipulated with tools.
in watchmaking, due to its low melting temperature (about 80–100 °C (176–212 °F)), 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.

-in the early twentieth century, it was used to protect some military rifle stocks.
-in Jelly Belly jelly beans, in combination with beeswax to give them their final buff and polish.
-in modern traditional archery, shellac is one of the hot-melt glue/resin products used to attach arrowheads to wooden or bamboo arrow shafts.
-Sanding sealer, is a solution of shellac dissolved in alcohol 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.
-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)
-in sculpture, to seal plaster and in conjunction with wax or oil-soaps, to act as a barrier during mold-making processes[citation needed]
-as a dilute solution in the sealing of harpsichord soundboards, protecting them from dust and buffering humidity changes while maintaining a bare-wood appearance.

Shellac resin, commercial resin marketed in the form of amber flakes, made from the secretions of the lac insect, a tiny scale insect, Laccifer lacca . 
Shellac resin is a natural thermoplastic; that is, a material that is soft and flows under pressure when heated but becomes rigid at room temperature. 
This property makes it useful either by itself or in combination with such fillers as flaked mica and asbestos in manufactured molding compositions, used for producing molded articles such as buttons.

Shellac resin is an ingredient in many products, including abrasives, sealing wax, hair sprays, and cake glazes. 
Shellac resin was formerly used, along with fine clay or other filler, to mold phonograph records, but, after the early 1930s, synthetic thermoplastics, particularly vinyl resins, gradually replaced it.
Alcohol solutions of Shellac resin, also called simply shellac, are used as varnishes for priming and finishing furniture, floors, and various wood articles and as an intermediate in nitrocellulose lacquers. 
Alkali emulsions of Shellac resin are used to make self-polishing waxes, stiffeners for felt hats, cements, and sealers.

Use and Manufacturing of Shellac resin
Shellac resin secreted by insects that feed on various resiniferous trees in India; Used mainly in lacquers and varnishes; Also to make buttons, grinding wheels, sealing wax, cements, inks, phonograph records, and paper; Also used to stiffen hats, coat confections and medicinal tablets, and finish leather; [Merck Index] Used as an anticaking agent, drying agent, humectant, processing aid, and surface-finishing agent for foods; [FDA] Permitted for use as an inert ingredient in non-food pesticide products; [EPA] Shellac is a natural bioadhesive polymer and is chemically similar to synthetic polymers, and thus can be considered a natural form of plastic.

Shellac resin is generally made from two ingredients, raw seed lac and ethyl alcohol. 
In fact, most companies want to purify shellac as completely as possible—impurities from the bug, the cocoon etc. are removed, as are natural waxes. 
Shellac resin is generally shipped in dry or flaked form and is re-moisturized with an alcohol solvent, generally denatured alcohol. 
Some companies add ingredients to lengthen the shelf life of their product but will not reveal these proprietary additives. 
Shellac resin that is bleached (or made into clear shellac) are dissolved in sodium carbonate and centrifuge to remove insolubles and then bleached with sodium hypochlorite.

Shellac resin is a natural product with interesting properties and an exceptional versatility. 
Shellac resin is the purified product of the natural resin lac which is the hardened secretion of the small, parasitic insect Kerria Lacca, popularly known as the lac insect. 
Shellac resin is the only known commercial resin of animal origin. 
Lac has been known in India and China since ancient times. 
Its use can be traced back to recordings from India from more than 2000 years ago. 
The first mentioning in Europe can be referred to van Linschoten in 1596 who was sent to India by the king of Portugal.

Shellac resin is a natural resin obtained from gum lac. 
Gum lac in turn is obtained from secretions of the female Kerria lacca insect. 
Production of shellac resin takes place mostly in China and India. 
The odorless and tasteless resin has a very high brittleness and hardness.

Shellac resin functions as a versatile wood treatment and coating, and acts as a binding agent in paint and rust treatment. 
Shellac resin is commonly used as a primer, basecoat or undercoat prior to painting, a knot and stain sealer and odour blocker, as well as a high-gloss wood varnish, being a key component of the French Polishing process. 
Shellac resin is also resistant to ultra-violet light, so does not darken with age, and is both quick drying and cures at relatively low temperatures. 
Damaged Shellac can simply be touched-up with a fresh coat of Shellac resin because the new one amalgamates with the existing coat. 
Brushes can be cleaned using methylated spirits.

First-aid measures

If inhaled : 
Move the victim into fresh air. 
If breathing is difficult, give oxygen. 
If not breathing, give artificial respiration and consult a doctor immediately. 
Do not use mouth to mouth resuscitation if the victim ingested or inhaled the chemical.

Following skin contact
Take off contaminated clothing immediately. 
Wash off with soap and plenty of water. 
Consult a doctor.

Following eye contact
Rinse with pure water for at least 15 minutes. 
Consult a doctor.

Following ingestion
Rinse mouth with water. 
Do not induce vomiting. 
Never give anything by mouth to an unconscious person. 
Call a doctor or Poison Control Center immediately.

Substance identity

EC / List no.: 232-549-9
CAS no.: 9000-59-3
Mol. formula: C30H50O11

Hazard classification & labelling of Shellac resin
Warning! According to the classification provided by companies to ECHA in CLP notifications this substance causes serious eye irritation, is harmful if swallowed, causes skin irritation and may cause respiratory irritation.

Shellac resin indicated, in 2009, as being intended to be registered by at least one company in the EEA.
Shellac resin for which classification and labeling data have been submitted to ECHA in a registration under REACH or notified by manufacturers or importers under CLP. 
Such notifications are required for hazardous substances, as such or in mixtures, as well as for all substances subject to registration, regardless of their hazard.

Shellac resin listed in the EINECS, ELINCS, or NLP inventories.

Synonyms:
SHELLAC
9000-59-3
(2R,6S,7R,10S)-10-hydroxy-6-(hydroxymethyl)-6-methyltricyclo[5.3.1.01,5]undec-8-ene-2,8-dicarboxylic acid;9,10,15-trihydroxypentadecanoic acid
Q429659
Shellac
Shellac
Shellac
shellac
SHELLAC A RESIN SECRETED BY LACCIFER LACCA, COCCIDAE
Shellac. A resin secreted by Laccifer lacca, Coccidae.
9000-59-3
(5ξ,10β)-10,14-Dihydroxycedr-8-en-12,15-disäure --9,10,15-trihydroxypentadecansäure (1:1) [German] [ACD/IUPAC Name]
(5ξ,10β)-10,14-Dihydroxycedr-8-ene-12,15-dioic acid - 9,10,15-trihydroxypentadecanoic acid (1:1) [ACD/IUPAC Name]
1H-3a,7-Methanoazulene-3,6-dicarboxylic acid, 2,3,4,7,8,8a-hexahydro-4-hydroxy-8-(hydroxymethyl)-8-methyl-, (3R,4S,7R,8S)-, compd. with 9,10,15-trihydroxypentadecanoic acid (1:1) [ACD/Index Name]
Acide (5ξ,10β)-10,14-dihydroxycédr-8-ène-12,15-dioïque - acide 9,10,15-trihydroxypentadécanoïque (1:1) [French] [ACD/IUPAC Name]
9000-59-3 [RN]
Lacca
Shellac