260 MADRAS FISHERIES BULLETIN VOL. XIII, 



5. Point I — Varnish. — The object of this class of lacquering is 

 to provide an elastic, durable, fairly solid coating to protect the 

 metal from the acids, etc., and able to stand a temperature above 

 that of boiling water (at Chaliyam of steam at 250° F.), without 

 melting or running; it must also contain no poisonous matter, e.g., 

 lead compounds (white lead, etc.), and have no taste which might 

 spoil the goods. Varnishes are either spirit or oil ; that is they 

 contain some "gum" (resin) such as copal, dammar, shellac, etc., 

 dissolved in either spirit or linseed oil. Spirit varnishes are very 

 readily applicable and dry very rapidly, but, by their very com- 

 position, they have neither body nor elasticity, and both of these 

 qualities are essential for our purpose. Hence o)ily a good oil 

 varnish must be used. In oil varnishes the resin plays a secondary 

 part ; it is the linseed oil which gives the solid, tough, elastic 

 coating, and, indeed, boiled linseed oil may almost be used alone. 

 Hence a varnish containing a large proportion of linseed oil is 

 essential. The copal oil-varnish of ordinary commerce, especially 

 with an addition of boiled linseed oil, is well suited, since it 

 consists of boiled linseed oil and a high class " gum " dissolved in 

 it ; the ensuing coating, after stoving, has the desired character- 

 istics ; it also bears stoving at the necessary temperature. A 

 similar oil-varnish prepared with " dammar " (the resin from the 

 Vateria Indica of the West Coast) is probably cheaper and may be 

 equally good, but has not been tried. 



It is advisable to buy the oil-varnish ready made from a good 

 maker, so as to secure goods made not only with good material 

 but with all the benefit of experience; much rubbish is sold in 

 India as "varnish " which never dries properly but remains sticky 

 and " tacky." It is not advisable to attempt to make the varnishes 

 one's self; it is a rather dangerous business, and requires much 

 knowledge, skill, and experience. 



6. Point 2 — Dilution of the oil-varnish. — This is a matter for the 

 canner's judgment. It is common when lacquering to add turps 

 to the commercial article; this renders it easy to work, but 

 thins the coating so that only a very thin layer results. It seems 

 advisable in lacquering cans for the special purpose of resisting 

 fruit acids or marinated articles, to add about 25 or 30 per cent of 

 thick boiled linseed oil to the commercial varnish, and then to thin 

 this with turps to allow of ready application to the tin with the 

 brush ; the turps soon evaporates from the layer, leaving a fairly 



