Painting defects: their causes and prevention; an address

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The Author, 1915 - Paint - 35 pages
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Page 16 - WIDE, DRYING IN THE OPEN AIR. Shrinkage inches 1 — All light conifers (soft pine, spruce, cedar, cypress) . 3 2 — Heavy conifers (hard pine, tamarack, yew) honey, locust, box elder, wood of old oaks 4...
Page 19 - We now come to the question of the prevention of cracking and scaling. It is to be noted that, as a rule, cracking and scaling take place most often when the paint film is thick. It may not occur on a first painting job, but when the work is repainted, cracking and scaling occur. The reason for this is obvious. The thicker the paint film, the stronger it is, that is the greater its tensile strength, and it cannot conform as readily to the changes in the shape of the wood. One method of prevention,...
Page 16 - Every joist and studding, every rafter, sash, and door, the chair we sit on, the floor we walk on, the wood of the wagon or boat we ride in, are all continually tested as to their stiffness and strength, their hardness and toughness. Every step...
Page 16 - ... the change in volume during drying is about equal to the sum of the radial and tangential shrinkage, or twice the amount of linear shrinkage indicated in the table. Thus, if the linear average shrinkage of soft pine is 3 inches per hundred, the shrinkage in volume is about 6 cubic inches for each 100 cubic inches of fresh wood, or 6 per cent of the volume.
Page 20 - ... conditions, it is probable that the paint which tends more to blister is the more impermeable. The one safe method of preventing blistering is to remove the cause, that is, the moisture in or back of the wood. In cold weather, wood may appear to be dry, and yet contain a great deal of moisture, which on a warm day will force its way to the surface. If one is in doubt as to the condition of wood for painting, the best practice is to allow considerable time after the priming coat has been put on...
Page 7 - One of these possible effects is the rupturing of this outer coat with consequent alligatoring or checking. The other possible effect is that the outer coat becomes thinner without rupturing. Which of these effects occurs depends upon the under coat. If the under coat is soft, the outer coat, in oxidizing and shrinking, will draw up and slip over it with consequent rupturing. If the under coat is sufficiently hard, the outer coat does not slip over it and simply becomes thinner by shrinkage, and...
Page 21 - ... moisture, which on a warm day will force its way to the surface. If one is in doubt as to the condition of wood for painting, the best practice is to allow considerable time after the priming coat has been put on before applying the body coat. It would appear in general that paint allows moisture to pass out through it to the atmosphere more than it allows moisture to pass the other way. This is probably largely due to the fact that we generally have more dry than moist weather. If a priming...
Page 16 - The reason for this difference in contraption parallel with and across the grain in the drying out of wood is easily understood with a little consideration. The structure of wood is largely fibrous, the fibers running mostly with the .grain. Free *, water or moisture in the wood is probably located between the * *• fibers. This water forces the fibers apart. As the water dries out, the fibers come closer together, producing contraction across the grain. It would appear also that the variation...
Page 8 - ... practicable, and to have these coats, relatively speaking, much harder than the outer coats. This is the practice in coach and carriage painting, where very little oil is used in the under coats, and, as we know, coach and carriage painting is perhaps the best type of painting there is. Now in the case of house painting, suppose we have checking and want to avoid it, how shall we proceed ? The answer is inevitable. We must so modify our under coats as to secure a hardness sufficiently greater...

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