VARNISH 1055 



hard coat, capable of resisting, iu a greater or less degree, tlie influences of air and 

 moisture. Such a coat consists of the resinous parts of the solution, which remain in 

 a thin layer upon the surface after the liquid solvent has either evaporated away, or 

 has dried up. When large quantities of spirit-varnish are to be made, a common 

 still, mounted with its capital and worm, is the vessel employed for coutaining the 

 materials, and it is placed in a steam- or water-bath. The capital should be provided 

 with a stuffing-box, through which a stirring-rod may pass down to the bottom of 

 the still, with a cross-piece to its lower end, and a handle or winch at its top. After 

 heating the bath till the alcohol boils and begins to distil, the heat ought to be'lowered, 

 that the solution may continue to proceed in an equable manner, with as little eva- 

 poration of spirit as possible. The operation may be supposed to be complete when 

 the rod can be easily turned round. The varnish must be passed through a silk sieve 

 of proper fineness ; then filtered through porous paper, or allowed to clear leisurely 

 in stone jars. The alcohol which has come over should be added to the varnish, if 

 the just proportions of the resins have been introduced at first. 



The building or shed wherein varnish is made, ought to be quite detached from any 

 buildings whatever, to avoid accidents by fire. For general purposes, a building about 

 18 feet by 16 is sufficiently large for manufacturing 4,000 gallons and upwards annually, 

 provided there are other convenient buildings for the purpose of holding the utensils, 

 and warehousing the necessary stock. 



Procure a copper pan made like a common washing-copper, which will contain from 

 50 to 80 gallons, as occasion may require ; when wanted, set it upon the boiling furnace, 

 and fill it up with linseed oil within 5 inches of the brim. Kindle a fire in the 

 furnace underneath, and manage the fire so that the oil shall gradually, but slowly, 

 increase in heat for the first two hours; then increase the heat to a gentle simmer; 

 and if there is any scum on the surface, skim it off with a copper ladle, and put the 

 skimming away. Let the oil boil gently for three hours longer ; then introduce, by 

 a little at a time, one quarter of an ounce of the best calcined magnesia for every 

 gallon of oil, occasionally stirring the oil from the bottom. When the magnesia is all 

 in, let the oil boil rather smartly for one hour ; it will then be sufficient. Lay a cover 

 over the oil, to keep out the dust while the fire is withdrawn and extinguished by 

 water ; next uncover the oil, and leave it till next morning ; and then while it is yet 

 hot, ladle it into the carrying-jack, or let it out through the pipe and cock ; carry it 

 away, and deposit it in either a tin or leaden cistern, for wooden vessels will not hold 

 it ; let it remain to settle for at least three months. The magnesia will absorb all the 

 acid and mucilage from the oil, and fall to the bottom of the cistern, leaving the oil 

 clear and transparent, and fit for use. Eecollect when the oil is taken out not to 

 disturb the bottoms, which are only fit for black paint. 



General Observations and Precautions to be observed in making Varnishes. Set 

 on the boiling-pot with 8 gallons of oil; kindle the fire; then lay the fire in the 

 gum-furnace ; have as many 8lb.-bags of gum copal all ready weighed up as will bo 

 wanted ; put one 81b. into the pot, put fire to the furnace, set on the gum-pot : in three 

 minutes (if the fire is brisk) the gum will begin to fuse and give out its gas. steam, 

 and acid ; stir and divide the gum, and attend to the rising of it, as before directed. 

 8 Ibs. of copal take in general from sixteen to twenty minutes in fusing, from the 

 beginning till it gets clear like oil, but the time depends very much on the heat of the 

 fire and the attention of the operator. During the first twelve minutes while the gum 

 is fusing, the assistant must look to the oil, and bring it to a smart simmer; for it 

 ought to be neither too hot nor too cold, but in appearance beginning to boil, which he 

 is strictty to observe, and when ready to call out, ' Bear a hand ! ' Then immediately 

 both lay hold of a handle of the boiling-pot, lift it right up so as to clear the plate, 

 carry it out and place it on the ash-bed, the maker instantly returning to the gum-pot, 

 while the assistant puts three copper ladlefuls of oil into the copper pouring-jack, 

 bringing ii in, and placing it on the iron plate at the back of the gum-pot to keep hot 

 until wanted. When the maker finds the gum is nearly all completely fused, and that 

 it will in a few minutes be ready for the oil, let him call out, ' Ready oil ! ' The assis- 

 tant is then to lift up the oil-jack with both hands, one under the bottom and the other 

 on the handle, laying the spout over the edge of the pot, and wait until the maker 

 calls out ' Oil ! ' The assistant is then to pour in the oil as before directed, and the 

 boiling to be continued until the oil and gum become concentrated, and the mixture 

 looks clear on the glass ; the gum-pot is now to be set upon the brick-stand until the 

 assistant puts three more ladlefuls of hot oil into the pouring-jack, and three more 

 into a spare tin for the third run of gum. There will remain in the boiling-pot still 

 3g gallons of oil. Let the maker put his right hand down the handle of the gum-pot 

 near to the side, with his left hand near the end of the handle, and with a firm grip 

 lift the gum-pot, and deliberately lay the edge of the gum-pot over the edgs? of the 

 boiling-pot, until all its contents run into the boiling-pot. Let the gum-pot be held, 



