First Varnish

A surface coating protects the substrate against abrasion, moisture, light, and corrosion. The binder for the pigment and extenders is fluid before application and rigid soon after. Natural binders range from gum arable to fish oil. The first varnishes were solutions of natural resins, having transparency, hardness, amorphous structure, and little permanence. 

Front-silvered mirrors can be pohshed with optical rouge on a pad of chamois leather over cotton wool. Care is necessary because it is easy to polish completely through the silver. Back-silvered mirrors can be protected by first varnishing the silver and then painting the varnish. Front-silvered mirrors can be protected with a thin coat of lacquer, such as a dilute solution of cellulose nitrate in amyl acetate. The lacquer should not be too thin, or interference colours may be produced. 

Although coatings technology was first described by Watin (Seymour, 1990) in his 1773 book, the first varnish factory was established in England in 1790. Shortly afterward, factories were established in several European nations and in the United States. Copal and amber continued to be the principal varnish resins and turpentine the thinner. 

The author wishes to dedicate this work to Mr. T. H. Shen of Yungkoo Paint Varnish Mfg. Co., Taipei, who gave him the rare opportunity of starting a new alkyd plant as the first job assignment for a fresh college graduate, and to the memory of the late chairman of the Department of Polymers Coatings, North Dakota State University, Dr. Alfred E. Rheineck, teacher, mentor, and friend. 

Cyclohexanol [108-93-0] is a colorless, viscous liquid with a camphoraceous odor. It is used chiefly as a chemical iatermediate, a stabilizer, and a homogenizer for various soap detergent emulsions, and as a solvent for lacquers and varnishes. Cyclohexanol was first prepared by the treatment of 4-iodocyclohexanol with ziac dust ia glacial acetic acid, and later by the catalytic hydrogenation of phenol at elevated temperatures and pressures. 

The first commercial applications of polypyromellitimides were as wire enamels, as insulating varnishes and for coating glass-cloth (Pyre.ML, Du Pont). In film form (Kapton) many of the outstanding properties of the polymer may be more fully utilised. These include excellent electrical properties, solvent resistance, flame resistance, outstanding abrasion resistance and exceptional heat resistance. After 1000 hours exposure to air at 300°C the polymer retained 90% of its tensile strength. 

At one time the small fragments of amber produced during the fabrication and machining operations were used to produce varnishes. In 1880 they were first used in the production of Ambroid. This is made by pressing the fragments in a hydraulic press at temperatures somewhat above 160°C. The moulded product has a close resemblance to amber. A form of extrusion has also been used to produce amber rods for subsequent conversion into pipe and cigarette-holder mouthpieces. 

In the case of the epoxypolyamide varnish, however, as the pH increased the resistance of the film at first rose, then at about pH 8.8 it started to fall until at pH 11 the change-over in the type of conduction occurred. This suggests that the resin was acting as a zwitterion with an isoelectric point at about pH 8.8. Thus before the isoelectric point the membrane would be positively charged and an increasing concentration of hydroxyl ions would... 

Triterpenoid resins used as varnishes on paintings were first studied with GALDI-MS by Zumbiihl et al. [3,4], He realised that freshly bought commercial resin, usually considered fresh , is actually in an advanced stage of oxidation. Additional experiments were performed later on with improved mass resolution that allowed more detailed conclusions [34 36],... 

The first synthetic polymers to be used as paint varnishes were acrylic and vinylic resins. Poly(vinyl acetate) (PVAc), commercialized under the name Mowilith by Hoechst and Vinylite by Union Carbide, has been used in conservation as an adhesive since 1932 and in 1937 it was proposed as a picture varnish by Stout and Cross [63]. PVAc was soon rejected as a varnish because, despite its light stability and good solubility in organic solvents, it demonstrated poor optical properties in terms of colour saturation and the tendency to pick up dirt due to its low glass transition temperature. 

Shellac, which was used by Edison for molding his first photograph records and is still used as an alcoholic solution (spirit varnish) for coating wood, is a cross-linked polymer consisting largely of derivatives of aleuritic acid (9,10,16-trihydroxyhexadecanoic acid). Shellac is excreted by small coccid insects Coccus lacca), which feed on the twigs of trees in Southeast Asia. Over 2 million insects must be dissolved in ethanol to produce 1 kg of shellac. 

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