A seal is a device for making an impression in wax, clay, paper, or some other medium, including an embossment on paper, and is also the impression thus made. The original purpose was to authenticate a document, or to prevent interference with a package or envelope by applying a seal which had to be broken to open the container.
Beeswax is a natural wax produced by honey bees of the genus Apis. The wax is formed into scales by eight wax-producing glands in the abdominal segments of worker bees, which discard it in or at the hive. The hive workers collect and use it to form cells for honey storage and larval and pupal protection within the beehive. Chemically, beeswax consists mainly of esters of fatty acids and various long-chain alcohols.
An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter or card.
Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low viscosity liquids. Waxes are insoluble in water but soluble in nonpolar organic solvents such as hexane, benzene and chloroform. Natural waxes of different types are produced by plants and animals and occur in petroleum.
Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. For several centuries the oil painting has been perhaps the most prestigous form in Western art, but oil paint has many practical uses, mainly because it is waterproof.
An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, forming a seal at the interface.
An oil pastel is a painting and drawing medium formed into a stick which consists of pigment mixed with a binder mixture of non-drying oil and wax. Oil pastel is a type of pastel. They differ from other pastel sticks which are made with a gum or methyl cellulose binder, and from wax crayons which are made without oil. The surface of an oil pastel painting is less powdery than one made from gum pastels, but more difficult to protect with a fixative. Oil pastels are bold and bright. They can be blended easily but they can break easily too.
Tamper-evident describes a device or process that makes unauthorized access to the protected object easily detected. Seals, markings, or other techniques may be tamper indicating.
A hermetic seal is any type of sealing that makes a given object airtight. The term originally applied to airtight glass containers, but as technology advanced it applied to a larger category of materials, including rubber and plastics. Hermetic seals are essential to the correct and safe functionality of many electronic and healthcare products. Used technically, it is stated in conjunction with a specific test method and conditions of use. Colloquially, the exact requirements of such a seal varies with the application.
A heat sealer is a machine used to seal products, packaging, and other thermoplastic materials using heat. This can be with uniform thermoplastic monolayers or with materials having several layers, at least one being thermoplastic. Heat sealing can join two similar materials together or can join dissimilar materials, one of which has a thermoplastic layer.
A cylinder seal is a small round cylinder, typically about one inch in length, engraved with written characters or figurative scenes or both, used in ancient times to roll an impression onto a two-dimensional surface, generally wet clay. According to some sources, cylinder seals were invented around 3500 BC in the Near East, at the contemporary sites of Uruk in southern Mesopotamia and slightly later at Susa in south-western Iran during the Proto-Elamite period, and they follow the development of stamp seals in the Halaf culture or slightly earlier. They are linked to the invention of the latter's cuneiform writing on clay tablets. Other sources, however, date the earliest cylinder seals to a much earlier time, to the Late Neolithic period in Syria, hundreds of years before the invention of writing.
A bulla is an inscribed clay, soft metal, bitumen, or wax token used in commercial and legal documentation as a form of authentication and for tamper-proofing whatever is attached to it.
Sealant is a substance used to block the passage of fluids through openings in materials, a type of mechanical seal. In building construction sealant is sometimes synonymous with caulk and also serve the purposes of blocking dust, sound and heat transmission. Sealants may be weak or strong, flexible or rigid, permanent or temporary. Sealants are not adhesives but some have adhesive qualities and are called adhesive-sealants or structural sealants.
Induction sealing is the process of bonding thermoplastic materials by induction heating. This involves controlled heating an electrically conducting object by electromagnetic induction, through heat generated in the object by eddy currents.
Vacuum packing is a method of packaging that removes air from the package prior to sealing. This method involves placing items in a plastic film package, removing air from inside and sealing the package. Shrink film is sometimes used to have a tight fit to the contents. The intent of vacuum packing is usually to remove oxygen from the container to extend the shelf life of foods and, with flexible package forms, to reduce the volume of the contents and package.
Lute was a substance used to seal and affix apparatus employed in chemistry and alchemy, and to protect component vessels against heat damage by fire; it was also used to line furnaces. Lutation was thus the act of "cementing vessels with lute".
Materials for use in vacuum are materials that show very low rates of outgassing in vacuum and, where applicable, are tolerant to bake-out temperatures. The requirements grow increasingly stringent with the desired degree of vacuum to be achieved in the vacuum chamber. The materials can produce gas by several mechanisms. Molecules of gases and water can be adsorbed on the material surface. Materials may sublimate in vacuum. Or the gases can be released from porous materials or from cracks and crevices. Traces of lubricants, residues from machining, can be present on the surfaces. A specific risk is outgassing of solvents absorbed in plastics after cleaning.
Packaging machinery is used throughout all packaging operations, involving primary packages to distribution packs. This includes many packaging processes: fabrication, cleaning, filling, sealing, combining, labeling, overwrapping, palletizing.
The lining of paintings is a process of conservation science and art restoration used to strengthen, flatten or consolidate oil or tempera paintings on canvas by attaching a new support to the back of the existing one. The process is sometimes referred to as relining. Most often a new support will be added directly to the back of an existing canvas. In cases of extreme decay, however, the original canvas may be completely removed and replaced. The height of the practice's use peaked in the late 19th century and in the following years its usefulness has been debated. There are many different factors that influence whether lining a painting will be successful. By paying close attention to an artwork's condition and response to treatment, conservation professionals better understand the lining process and when to apply it.
Letterlocking is the act of folding and securing a written message on papyrus, parchment, or paper, without requiring it to be contained in an envelope or packet. It is a traditional method of document security that utilizes folding and cutting. The process dates to the 13th century in Western history, corresponding with the availability of flexible writing paper.
