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use of ,i piece of iron heated to redness, an angle or corner of which is to be applied to the tube at the point where it is to be cut, and then, if the fracture is not at once effected by the action of the hot iron, plunge suddenly into cold water. After having made a notch with a file, or the edge of a flint, you introduce into it a little water, and bring close upon it the point of a wire, previously heated to the melting point. This double application of heat and moisture obliges the notch to fly round the glass. Glaziers use for cutting glass a diamond splinter mounted in a holder.
To Draw on Glass.—Grind lampblack with gum-water and some common salt; draw the design with a pen or hair pencil; or use a crayon made for the purpose.
Stencilling' on Glass — Writing on Glass.—Stencil plates may be cut out of thin sheets of metal or cardboard, in the same manner as for wall decoration, &c. If varnish colours are employed, lay them on as evenly as possible, through the perforations in the plate, and harden afterwards in a stove or oven. The metallic preparations used in glass staining and painting are also available, but require firing in a muffle, or a china painter's stove. Should the process.commonly called embossing be wanted, paint the portions of glass left uncovered by the spaces in the stencil plate with Brunswick black, dip or cover with hydrofluoric acid, wash in clear water and remove the black ground. Every part that was covered will then present a polished even surface, the remainder will have been eaten into by the acid. If the raised parts are to have a frosted appearance, rub them with a flat piece of marble moistened with fine emery and water. For putting patterns or lines on glass with a wheel, there are two methods, one followed by glass cutters, the other by the engravers on glass. The first-mentioned, rough in the pattern, with an iron mill supplied with a trickling stream of sand and water, smooth out the rough marks on a wheel of York or Warrington stone, polisn on a wooden wheel of willow or alder
moistened with pumice powder, and finish on a cork wheel with putty and rottenstone. The engraver cuts in and roughs the prttern with copper wheels, aided by emery of various degrees of fineness, and olive or sperm oil, and polishes the portions intended with leaden disks and very fine pumice powder and water.
Painting Glass for the MagicLantern.—Draw on paper the size of the glass the subject you mean to paint. Fasten this at each end of the glass with paste, or cement, to prevent it from slipping. Then reverse the glass so as to have the paper underneath, and with some very black paint, mixed with varnish, draw with a fine camel-hair pencil very lightly the outlines sketched on the paper which are reflected on the glass. It would add to the natural resemblance if the outlines were drawn with a strong tint of each of the natural colours of the object; but in this respect the artist must please hia fancy. When the outlines are dry, colour and shade the figures; but observe to temper the colours with strong white varnish.
Pigments for Magic Lantern Slides.—The only pigments available are the transparent and a few of the semi-transparent. The transparent include (beginning with the best for the purpose) Prussian blue, gamboge, carmine, verdigris, madder brown, indigo, crimson lake, and ivory black. The semi - transparent include raw sienna, burnt sienna, cappah brown, and Vandyke brown. No particular method of mixing the colours is requisite. Ordinary oil or water colours will do, but they must be ground extremely fine. The pencils must be small and their points unexceptionable. Camel's-hair is preferable to sable for painting upon glass, its elasticity being less, and the trouble of working out the brush marks, which must always be carefully attended to, not so great. The best vehicle to use for thinning the colours is ordinary megilp, and not a drop more than is necessary for properly working should be added, for if the colours be made too thin they will run into each other and utterly ruin the painting. If water colours are preferred, the best medium for laying or. the first wash of colour is a hot solution of transparent gelatine. When this is dry and cold it admits of shading and finishing without being disturbed, provided the pencil be handled gently and the medium be cold water. The oil paintings require no Tarnishing, but the transparency of the water colours is much heightened by a thin coat of the purest mastic varnish. In colouring the pictures the quality of the light which is to show them must be borne in mind. If it be the lime light, approximate as nearly as possible to nature; but if it be the light of an oil lamp, remember that its rays are greatly deficient in blue, the yellow proportionately preponderating, and arrange the tints accordingly: for instance, the greens must be much bluer than natural, the yellows must incline to orange, and all shades of violet (the complementary of yellow) wholly eschewed.
Glass Cleaning'.—Grease may be dissolved from glass by means of carbonate soda, carbonate potass, or better still, by caustic soda, made thus:—10 parts of carbonate soda are dissolved in 100 parts of water (10 oz. to 100 oz.), and heated to ebullition in a clean nntinncd iron vessel; 8 parts of good quicklime are meanwhile slaked in a covered basin, and the resulting hydrate of li'.ne added, little by little, to the boiling solution of carbonate, with frequent stirring. This will give a very strong caustic solution, and should be used with care. Keep your hands out of the solution, and dip the glass in by means of the pliers, keeping them moving while in the solution. When the grease is dissolved or loosened, scrub with a brush, well rinse Id water, and dry.
Frosting Glass.—Roll up tolerably tightly a slip of tin, about 6 in. or 8 in. long and about 2 in. broad, or use a small flat piece of marble. Dip either of these in Croydon or glass-cutter's sand, moistened with water; rub over the glass, whether flat or round, dipping it frequently in a pail or pan of clear water. This is the method employed for frosting jugs, &c. For lamp glasses a wire brush
is used, and they are chucked in a lathe. Pane& of glass should be laid on a soft bed of baize, or coarse linen. If the frosting is to be very fine, finish with washed emery and water. As a temporary frosting for windows. mil together a strong, hot solution of suipj&3.te of magnesia and a clear solution of gum arable, appiy warm. Or use a strong solution of sulphate of sodium warm, and when coo] wash with gum-water to protect the sur face from being scratched.
Drilling Glass. — Glass can be drilled with a common drill, but the safest method is to use a brooch drill. No spear-pointed drill can be tempered hard enough not to break. The brooch can either be used as a drill with a bow, or by the hand. It should be selected of such a bore that it will make a hole of the required size, at about one inch from the end. It should be broken off sharp with a pair of pliers, at about an inch and a half, and when the sharp edges are blunted by drilling, a fresh end should be made by breaking off an eighth of an inch, and so on, until the hole is bored. It is always desirable to drill from both sides, as it prevents the glass from breaking; drill lightly, and lubricate with spirits of turpentine and oil of lavender, or a little camphor instead of oil of lavender. Holes may be drilled through plate glass with a flat-ended copper drill and coarse emery and water. The end of the drill will gradually wear round, when it must be re-flattened, or it will not hold the emery. Practically, however, the best means of drilling holes in glass is by using a splinter of a diamond. A brass drill is made to fit the drill-stock, sawn down a little way with a notched knife to allow the splinter to fit tight, and the splinter fixed in the split wire with hot shellac or sealingwax. The drill is to be used quite dry and with care. If the hole to be drilled is wanted larger than the tool, drill a number of small holes close together to form a circle as large as the hole required, then join the holes with a small file. A splinter of diamond may be bought for 2s. (or 50) bi, enough to drill a J in. hob.
Darkening Glass.—The following, if neatly done, renders the glass obscure yet diaphanous :—Rub up, as for oil colours, a sufficient quantity of sugar of lead with a little boiled linseed oil, and distribute this uniformly over the pane, from the end of a hog-hair tool by a dabbing, jerking motion, until the appearance of ground glass is obtained. It may be ornamented, when perfectly hard, by delineating the pattern with a strong solution of caustic potash, giving it such time to act as experience dictates, and then expeditiously wiping out the portion it is necessary to remove.
Bending Glass Tubes. — If a sudden bend is wanted, heat only a small portion of the tube to a dull red-heat, and bend it with the hand held at the opposite ends. If the bend is to be gradual, heat an inch or two of it in length, previous to bending it. If a gradual bend on the one side, and a sharp one on the other, as in retorts, a little management of the tube in the flame, moving it to the right and left alternately at the same time that it is turned round, will easily form it of that shape. In bending glass, the part which is to be concave is to be the part most heated. An ordinary gas flame is quite sufficient to bend glass by, but that of a spirit lamp is better.
Glass, to Powder.—Make a piece of glass red hot in the fire, and while in ihis state plunge it into cold water; it will immediately break into powdtr; this must be sifted and dried; it is then fit for making glass paper, for filtering varnishes, and for other purposes.
Manufacture of Varnishes.— The building in which varnish is made ought to be quite detached from any other building whatever, and have a door-way in the centre with folding doors made to lift off the hinges. Let the roof of the building slope to the front; fix also in each end wall a frame and door made to lift off the hinges, so that, when necessary, there may be a free draught through the premises. Let three skylights be made and fixed in the roof, not directly over the furnaces, but on one side, so as to throw light on the furnaces. The skylights and flaps must
lower part of the cylinder is then riveted to the bottom with copper rivets, the heads of which are inside, and project through the lappings of the copper, flattened on both sides. Previous to riveting on the bottom, a flange of copper, of about | in. in thickness, is fixed on to the bottom part, under the large rivets: it is fixed horizontally round the pot. Also previous to riveting on the bottom, put on the iron hoop d, 1J in. in breadth, to which is welded an iron handle, made 1 in. broad by 1 in. thick, gradually increasing to 2 in. in breadth, but decreasing in thickness. The length from pot to handle end 2 ft. 8 in.
Boiling pot.—Procure a copper pot e to fit furnace, Fig. 8, the bottom to be beat out of the solid, as the gum pot, and of the following dimensions: Diameter across the bottom outside, 20 in.; height of bottom, 7 in.; the cylindrical or body part of the pot to be 2 ft. 10 in. in depth, and joined to the bottom part with stronp copper rivets, made to project through at least three-quarters of an inch, and to be well hammered inside and out; for, as there is no flange, the rivets must be large and strong to support the weight
of the pot and its contents while boiling on the furnace plate. It ought to fit the plate neatly, yet so easy as to lift or? freely. Seven inches below the mouth of the pot fix on two strong iron handles, one on each side, riveted through each end with two strong rivets; the space for the hands to be 7 in., and 1J in. in diameter, and to project 4 in. from the pot sides.
Small Tools.—In addition to the furnaces the varnish manufacturer requires two copper ladles, made to hold two quarts each, with turned hardwood handles. Two good ladles for the iron set pot, made of sheet copper or sheet iron, with ash handles. For a pot of 40 gallons, or upwards, the ladle to hold 3 quarts. Two copper stirrers, Fig. 5, made from three-quarter diameter copper rods 3J ft. long, beat flat at the one end to l1 in. breadth, 8 in. up the rod; to be finished with ferrulcd handles 7 in. in length. One large, strong, copper funnel, with lapped seams, for straining boiling varnish or oil; tin or soldered funnels would melt. One copper oil-jack, Fig. 6, which will contain 2 gallons, for pouring in hot or boiling oil, with a large strong pitcher handle, and spout in front. One brass or copper sieve containing 60 meshes to the inch, 9 in. diameter, for straining the first varnish. A brass sieve, 40 meshes to the inch, 9 in. diameter, for straining gold size, tur pentine, varnish, boiled oil, &c. A brass sieve, 40 meshes to the inch, and 9 in.
varnish. A 3-gallon tin jack, made with a strong handle at back, and a large broad spout in front; used for receiving the washings when poured out from the gum pot. A small broom, termed a swish, made from the waste cuttings of cane tied on a small handle, like a hearth broom, for washing out the gum pot each time it is used; to be always kept clean, and left in oil of turpentine. An iron trevet, made with a circular top 14 in. diameter, with four small cross-bars; the three feet of the trevet 12 in. high; it is used for setting the gum pot upon, with its bottom upwards, for a minute between each running.
Boiling Linseed Oil.—Procure a copper pan, Fig. 9, made like a common washing copper, set it upon the boiling furnace, Fig. 8, and fill 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 skimmings away. Let the oil boil gently for three hours longer, then introduce, by a little at a time, a
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 drawn and extinguished by water; then 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 wood 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, transparent, and fit for use. Recollect, when the oil is taken out, not to disturb the bottoms, which are only fit for black paint.
M Akins Varnish On A Small Scale. —First procure a gum pot, Fig. 4, or smaller, if required; then a three-footed iron trevet with a circular top, the feet 16 in. in length, and made to stand wider at the bottom than at the top, which is to be made so that the pot will fit easily into it. Place the trevet in a hollow in a yard, garden, or outhouse, where there can be no danger from fire; raise a temporary fire-place round the trevet with loose bricks, after the same manner that plumbers make their furnaces; then make up a good fire with either coke, coal, or wood-charcoal, which is far preferable; let the fire burn to a good strong heat, set on the gum pot with 3 lbs. gum copal; observe, that if the fire surround the gum pot any higher inside than the gum, it is in great danger of taking fire. As soon as