The following compound has a glazed surface when dry, which is sometimes pre ferred : — Oxidized linseed oil, 2k cwt.; rosin, 2 cwt. 21 lb.; Eauri gum, 105 lb. ; red-lead, 11 cwt. ; Venetian red, 2 cwt.
21 lb. ; shellac, 58 lb. ; litharge, 18 lb. ; naphtha, 20 gal. ; methylated spirit, 5 gal.
The materials are mixed for about 6 hours in a steam-heated pan, furnished with a steam-tight lid above and a tap below, and should be continually stirred. It has been claimed for this mixture that it is waterproof, but, as a matter of fact, it does not resist moisture so well as the size back ing, and has the disadvantage of sticking to the face of the cloth in hot weather.
The backing was formerly applied by hand as in the manufacture of oilcloth, but the operation can be much more rapidly and completely performed by a machine, a side view of which is given in Fig. 713. The backing is placed in the pan a, the lid of which is movable, and the bottom steam- jacketed. The pan should never be more than half-full. The shaft b is furnished with stirrers, which revolve in the backing, and prevent the pigment from settling. Through the tap c, the backing falls upon the back of the linoleum f, and is distributed roughly upon it with the help of a trowel. The cloth is carried upwards by means of a roller, covered with carding wire, which works against its face. The spreader d is steam heated, in order to keep the backing liquid, and is fitted with a steel scraper, which presses the liquid into tho canvas, and removes all excess. The quantity of backing spread upon the cloth is regulated by the screw c raising or lowering the roller g, upon which the face of the linoleum runs. The roll of linoleum h is inserted as it arrives from the rolling-machine. The linoleum is allowed to hang for about 12 hours, or till the backing is dry, and is then ready for printing, nr for seasoning if it is to be need plain.
The seasoning buildings or stoves are about 30 ft. in height, sud are furnished with heating apparatus, so that the temperature may be kept at about 24° (75° F.). The cloth is hung in loops or bights upon racks, each bight being supported on battens. Fig. 714 shows the arrangement of
these battens, A being a top view and B a section of part of a " bay " or division in a season ing stove ; u is the batten, the construction of which is shown in C. The material is thin sheet iron e, each end being filled up and strengthened by a piece of wood, fastened by the nails or screws f. These battens are not made perfectly straight, but have a slight curve or ember upwards when in place. The amount of camber is so calculated Clint as soon as the linoleum is bung upon the battens its weight straightens them. If the battens were made quite straight in the first instance the weight of the fabric would depress them in the centre, producing a convexity of surface in the linoleum, which would prevent its lying flat. The camber of the battens must he tested periodically with a templet, as the iron is liable to become bent. All lateral movement of the battens is prevented by the laths c. Wooden battens have been used, but they frequently crack and warp, owing to the high temperature in the buildings.
The method of hanging from battens, although most prevalent, bas several disadvantages. The linoleum, especially when fresh from the rolling-machiue, softens, on account of the high temperature to which it is exposed, and its weight stretches the top part of each bight. For this reason the height of a " bay " should not exceed 25 ft. It is very difficult to maintain a uniform temperature at both top and bottom of so high a building as a seasoning stove, the consequence being that the upper part of a bight will be the more thoroughly seasoned, unless the position of the cloth be reversed during the process. Flat, horizontal racks have been adopted to avoid these defects. They are construoted of hoop-iron, the racks or trays for the reception of the cloth being about 3 in. apart. The pieces of linoleum are drawn into them by a rope, which may be driven by a small winding-engine. For plain linoleum these flat racks have proved successful, but with printed goods they are very liable to smear the wet paint during the drawing in.