Preparation of varnish

Answer 1

Varnish is a thin transparent liquid that is prpared by mixing drying oil, resin and a thinner or solvent. Drying oil is obtained from linseed oil, tung oil and walnut oil which contains high level of poly unsaturated fatty acids. Resin obtained from amber, Kauri gum, dammar, copal, rosin, balsam etc are used. The solvent added include the natural turpentine or the chemical paint thinner. This when applied on wood has a glossy finish. It protects the wood from damage.

Answer 2

amber gum is heated to a temp. of 650*c in a iron kettle.it is then cooled to 500*c and china wood oil is added.the mixture is again heated to 560*c and linseed oil is added.It is cooled to room temp.and spirit is added.the varnish will dry to touch in about 4 hour and hard in about 8 hour.

Answer 3

Bottom of Form

There are two principal kinds of varnish, spirit and oleo-resinous. The most important spirit varnish is a solution of shellac in alcohol;

Shellac the American standard is made by dissolving five pounds of shellac in a gallon of alcohol; but this is too heavy for common use, and three and a half pounds is more generally suitable. Shellac is naturally dull orange-yellow in color, and is called orange shellac in distinction from white shellac, which is the same bleached with chlorine.

It is of better quality before bleaching, but, of course, darker in color. Orange shellac varnish may be made in an earthen jar, half full of alcohol; to each gallon of alcohol weigh out three and a half pounds of dry shellac (gum-shellac), in flakes, and at night gently drop this into the alcohol. Do not on any account stir it, not even once. Cover it, and next morning stir it with a stick; avoid anything with iron, as iron quickly discolors it. Once an hour stir it for a minute or two, and by night it will be dissolved.

White shellac is dissolved in a churn, or in a vessel where it is agitated with a mechanical stirrer. Orange shellac will dissolve in 85 per cent alcohol, though stronger alcohol is better; but white requires 95 per cent. White shellac resin does not keep well; it is liable to become insoluble, and should be dissolved as soon as purchased. In spirit varnishes the liquid, or vehicle, is volatile and serves as a means of spreading the resin in a thin, uniform film. Damar is another spirit varnish, and is a solution of damar resin in turpentine.

Fixatives ; Oleo-resinous varnishes are made by dissolving certain resins in linseed oil, with the aid of heat; and as one effect of the resinous resin is to thicken the oil, they are thinned with turpentine (or a substitute). The larger the proportion of resin, the quicker they are to dry, also the harder and more lustrous, but also the less elastic and durable. The best of these are more durable than the spirit varnishes. The dark-colored varnishes are less costly than the paler ones, because the clear, transparent resins are more rare and expensive; but they are just as good in everything but color, and for many purposes this is no objection, as where they are used over dark wood, or as an ingredient of paint (except pure white paint).

The resins used in varnish-making are of vegetable origin, and come from the warmer parts of the earth, mostly from Africa, the Philippine Islands, and from Brazil; though one important and valuable resin comes from New Zealand, which is outside the tropics. They have formed lumps on the trees, as spruce-gum is found on spruce trees in this country, but in larger pieces; but for the most part they are dug up from the earth, the trees which produce them having long ago fallen and decayed, and by being long buried in the earth the resin has become harder and more valuable. Fresh resins are, as a rule, too soft to make good varnish. They are of many different kinds, and are believed to have been produced by various hardwood trees.

Answer 4

Varnish typically consists of a solvent, a resin, and sometimes additives like drying agents or UV inhibitors. To prepare varnish, dissolve the resin in the solvent while stirring continuously to create a smooth mixture. Add any desired additives according to the manufacturer's instructions and continue stirring until well combined. Strain the varnish to remove any impurities before use.