. The art of lead burning; a practical treatise explaining the apparatus and processes. inverted seam shows pitsupon examination of the reverse side of thesheets. These are caused by overheating. Theoperator will often be surprised at the invertedbutt seam showing a remarkable fullness. Thisis accounted for upon the examination above re-ferred to. The lead, upon the application of theheat, runs from the upper or back side of thesheet and forms a very full seam. For that rea-son the inverted butt seams always appearstronger than they really are. See inverted lapseam. Fig. 27. Lap Seams. The lap
. The art of lead burning; a practical treatise explaining the apparatus and processes. inverted seam shows pitsupon examination of the reverse side of thesheets. These are caused by overheating. Theoperator will often be surprised at the invertedbutt seam showing a remarkable fullness. Thisis accounted for upon the examination above re-ferred to. The lead, upon the application of theheat, runs from the upper or back side of thesheet and forms a very full seam. For that rea-son the inverted butt seams always appearstronger than they really are. See inverted lapseam. Fig. 27. Lap Seams. The lap seams are the seams commonly used onall classes of work. When the beginner becomesproficient with the blow pipe no trouble will beexperienced in making lap seams that will show 92 THE ART OF LEAD BURNING. when cut a joint equal in thickness to the sheetsthat are joined. The lead sheets for the flat lapseam are prepared by shaving clean the exposededge; also, shave the sheets where they toucheach other. The upper edges can then be shavedfor a distance of % inch each side of the lap,. Fig. 27.—Burning an Inverted Lap Seam. which will make the finished seam ^ inch wide,as shown at a in Fig. 23. The sheets should belapped y2 to ^4 inch, according to the weight ofthe stock. It is very evident that light weightswould not require as large a lap as would heav-ier sheets, as the object of lapping the sheets isto leave the sheets practically as one piece, and THE ART OF LEAD BURNING. 93 the lead, to accomplish this object, is to be meltedfrom the upper sheet. From the foregoing it will be seen why a 12-pound sheet requires a ^-inch lap, while a 24-pound sheet would require a ^-inch lap. Theflame, when regulated to the work, is brought tobear squarely on the edge of the upper sheet,slanting slightly in the direction of the lowersheet, as shown. When the edge has brightenedalmost to the fusing point the blow pipe shouldbe drawn quickly to one side and from the uppersheet to the lower sh
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