Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/107

Rh V A R V A R 91 VARNHAGEN VOX EXSE, KARL AUGUST (1785- 1858), German biographer, was born at Dlisseldorf on 21st February 1785. He went to Berlin to study medicine, but devoted his attention chiefly to philosophy and literature, Avhich he afterwards studied more thoroughly at Hamburg, Halle, and Tubingen. He began his literary career in 1 804 as joint-editor with A. von Chamisso of a Musen- ahnanach. In 1809 he joined the Austrian army, and was wounded at the battle of Wagram. Soon afterwards lie accompanied his superior officer, Prince Bentheim, to Paris, where he carried on his studies. In 1812 he joined the Prussian civil service at Berlin, but in the following vear resumed his military career, this time as a captain in the Russian army. He accompanied Tettenborn to Hamburg and Paris, and his experiences were recorded in his Geschickte der Hamburger Erdgnisse (1813) and his fj eschichte der Kriegsziige Tettenborn s (1814). At Paris he entered the diplomatic service of Prussia, and in 1814 acted under Hardenberg at the congress of Vienna. He also accompanied Hardenberg to Paris in 1815. He w r as resident minister for some time at Carlsruhe, but was recalled in 1819, after which he lived chiefly at Berlin as a privy councillor of legation (Geheimer LegationsratJi). He had no fixed official appointment, but was often employed in important political business. In 1814 he married Rahel Antonie Friederike, originally called Levin, afterwards Robert. She was born in 1771 at Berlin, where she died in 1833. By birth she was a Jewess ; but before her marriage she made profession of Christianity. Although she never wrote anything for publication, she was a woman of remarkable intellectual qualities, and exercised a powerful influence on many men of high ability. Her husband, who was devotedly attached to her, found in her sympathy and encouragement one of the chief sources of his inspiration as a writer. After her death he published a selection from her papers, and after wards much of her correspondence was printed. Varn- liagen von Ense never fully recovered from the shock caused by her death. He himself died suddenly in Berlin on 10th October 1858. lie made some reputation as an imaginative and critical writer, Imt lie is famous chiefly as a biographer. He possessed a remark able power of grouping facts so as to bring out their essential significance, and his style is distinguished for its strength, grace, and purity. Among his principal works are Goethe in den Zcwj- iiissen der Mitlebcndcn (1824) ; Biorjraphisclie Dcnkmalc (five vols., 1824-30); and &quot;Lives&quot; of General von Seydlitz (1834), Sophia Charlotte, queen of Prussia (1837), Field-Marshal Schwerin (1841), Field - Marshal Keith (1844), and General Billow von Dennewitz (]853). His Denkiviirdigkeiten nnd vermisclitc Schrifte.n appeared in seven volumes in 1837-46. After his death were published two additional volumes of Dcnkwurdigkcitcn, some volumes of his corre spondence with eminent men, his Tarjcbucher (14 vols.), Blatter mis der prcussischen Gcschichtc (5 vols. ), and Eiographischc Portrdts. His selected writings appeared in nineteen volumes in 1871-76. VARNISH. A varnish is a fluid preparation which, when spread out in thin layers, dries either by evapora tion or by chemical action into a hard, transparent, and glossy film. Varnishes are used to communicate lustre and brilliance to many different kinds of dressed surfaces, metal-work, wood, paint, paper, leather, etc., and to protect such surfaces from the influence of air and damp. The chief requisites of a good varnish are that it forms a firmly-adherent layer on the surface over which it is spread, that it dries hard, yet with sufficient elasticity and tenacity not to crack with changes of temperature, that it forms a glossy durable surface, and that it dries quickly. The materials which almost exclusively form the permanent body of varnishes are the drying oils and resinous sub stances, the chief of which are the copals, lac, dammar, olemi, amber, sandarac, mastic, and rosin. For certain forms of varnish the drying oils themselves act as the solvent for the resins, but in other cases volatile solvents are employed. The solvents chiefly used are methylated spirit, wood spirit, ether, benzin, and turpentine and other essential oils. Soluble colouring ingredients are also, in some cases, used in varnishes and lacquers, those principally available being gamboge, dragon s blood, aloes, cochineal, turmeric, and coal-tar dyes. According to the solvents employed, the ordinary kinds of varnish are divided into three classes, (1) spirit, (2) turpentine, and (3) oil varnishes. Spirit varnishes dry with great rapidity owing to the volatilization of the solvent spirit, leaving a coating of pure resin of great hardness and brilliance, but the film is deficient in tena city, cracking and scaling readily on exposure. The resin lac, either as grain, shell, or bleached lac, is the basis of most spirit varnishes ; but sandarac is also largely used, and to these are added in varying proportions the softer resins, elemi, Venice turpentine, Canada balsam, mastic, etc., which give elasticity and tenacity to the varnish. The solvent is almost exclusively methylated spirit. The resins are ground and mixed with powdered glass, which prevents the resinous particles from agglutinating, and thus facilitates the solvent action of the spirit. The solu tion is effected by agitation in closed vessels with the aid of heat, and the varnish when strained off must be kept tightly closed from the air. Spirit varnishes are used principally for cabinet-work and turnery, stationery, gilding, and metal-work. Coloured spirit varnishes and lacquers are largely employed for metal- work, for imita tion gilding and bronzing, for toys, Arc. Turpentine is the solvent principally used for making dammar varnish, the solution being effected by powdering the resin and boiling it with a proportion of spirit of turpentine, after which more turpentine is added in the cold state to bring the preparation to a proper consistency. To increase the tenacity of such dammar varnish some proportion of boiled linseed oil or of oil copal varnish may be added. In place of oil of turpentine other essential oils may be used as solvents, and in practice oil of spike is largely utilized in preparing fine varnishes for oil paintings. Turpentine varnishes are also made in which the principal resinous bodies are sandarac and common rosin ; and, moreover, turpentine is largely employed to reduce the consistency and to improve the drying properties of copal varnishes. The basis or solvent of oil or fatty varnishes consists principally of linseed oil ; but the other drying oils poppy and w 7 alnut, ic. may also be used. These oils, without the addition of resins, themselves form varnishes which on exposure in thin layers dry by a process of oxidation into tough glossy films ; but the drying proceeds very slowly unless the oils are previously boiled with the red oxide of lead or otherwise treated to increase their power of absorb ing oxygen (see LINSEED OIL, vol. xiv. p. 677). It is in the form of boiled oil or of oil prepared with driers that these oils are used in. varnish-making. Oil varnishes thus differ from the other classes in the circumstance that the principal solvent is not volatile and dissipated on exposure, but in itself forms an essential and permanent ingredient in the preparation. The resin principally used in oil varnishes is copal, and its varieties differ very much in hardness, that is, in the temperature at which they melt and distil. Hard and semi-hard copals can only be made to mix with and dissolve in oils at the temperature at which they distil, which ranges from 230 to 360 C. The copal in varnish-making is melted and brought to the requisite temperature in a copper vessel. Simultaneously the oil is heated to the boiling-point in a separate copper vessel, and at the proper moment a measured quantity of the boiling oil is added to the liquefied resin. They are then boiled together till the mixture becomes perfectly clear, and by a series of alternate additions of oil and