INTERACTING ICT ACROSS THE CURRICULUM TASK 2: POWERPOINT PRESENTATION NAME: Navitalai Logaivau ID#

DEFECTS IN TIMBER

DEFINITION A defect is an IRREGULARITY or ABNORMALITY occurring in or on wood which is responsible for its A defect is an IRREGULARITY or ABNORMALITY occurring in or on wood which is responsible for its Strength reduction Strength reduction Lowering of durability Lowering of durability Lowering of usefulness or value Lowering of usefulness or value Poor appearance Poor appearance Decay Decay

CLASSIFICATION OF DEFECTS CAUSES DUE TO Natural Forces InsectsFungiConversionSeasoning

NATURAL FORCES

Chemical Stain Chemical Stain The wood is sometimes discolored by the chemical action caused with it by some external agency. This is known as the chemical stain The wood is sometimes discolored by the chemical action caused with it by some external agency. This is known as the chemical stain Rind Galls Rind means ‘Bark’ and Gall means ‘Abnormal Growth’. Peculiar curved swelling found on the body of a tree are known as Rind Gall. The timber in this part is very weak.

FUNGUS AND INSECTS

DRY ROT This is caused by a fungus growth which lives on the wood and thus destroys it. It attacks wood in damp, unventilated positions causing it to dry up and crumble into dust. This is caused by a fungus growth which lives on the wood and thus destroys it. It attacks wood in damp, unventilated positions causing it to dry up and crumble into dust. 8

FUNGUS ATTACK There are some more or less harmless fungi which affect timber. The result is usually to stain the wood with grey streaks or patches. This kind of fungus spoils a decorative white wood like Kauvula. There are some more or less harmless fungi which affect timber. The result is usually to stain the wood with grey streaks or patches. This kind of fungus spoils a decorative white wood like Kauvula. 9

INSECT ATTACK 10

INSECT ATTACK 11

INSECT ATTACK There are several varieties of insect that attack wood. One that does serious damage to furniture is the common furniture beetle. It’s length is about 2.5 – 5mm long. There are several varieties of insect that attack wood. One that does serious damage to furniture is the common furniture beetle. It’s length is about 2.5 – 5mm long. The beetle lays its eggs in cracks and crevices of the wood. These hatch into small worms which burrow into the wood. They continue to eat their way through the wood for up to two years. The worms then change into beetles and come out leaving a woodworm hole. The beetle lays its eggs in cracks and crevices of the wood. These hatch into small worms which burrow into the wood. They continue to eat their way through the wood for up to two years. The worms then change into beetles and come out leaving a woodworm hole. 12

INSECT ATTACK It is thus possible for wood to be affected by woodworm for a long time before the woodworm holes are seen. It is thus possible for wood to be affected by woodworm for a long time before the woodworm holes are seen. The beetles are very small-about the size of a pin head-and light brown in colour. The beetles are very small-about the size of a pin head-and light brown in colour. They are active in the summer months and during this time they fly about and lay their eggs on furniture. They are active in the summer months and during this time they fly about and lay their eggs on furniture. They are very fond of the plywood backs of cupboards. They are very fond of the plywood backs of cupboards. Although little can be done about the worms in the wood, several preparations are on the market which poison the beetles as they come out and destroy any eggs laid" on the surface. Although little can be done about the worms in the wood, several preparations are on the market which poison the beetles as they come out and destroy any eggs laid" on the surface. 13

CONVERSION DEFECTS

KNOTS Where a branch has grown out of a tree the grain in the trunk becomes very twisted. When this is cut through during conversion the result is a weaker board and one which is difficult to work. Dead knots occur in some softwoods Where a branch has grown out of a tree the grain in the trunk becomes very twisted. When this is cut through during conversion the result is a weaker board and one which is difficult to work. Dead knots occur in some softwoods 15

SHAKES These are splits along the grain of the wood. Heart shakes and star shakes are very similar; they radiate from the centre or heart (see drawing) 16

SHAKES Cup or ring shakes follow the annual rings. 17

SHAKES End splits are caused by rapid drying from the end grain Shakes may occur during the felling or as a result of faulty seasoning. 18

WANEY EDGE When the outside of the tree is left as part of a board it is called the waney edge.. 19

SEASONING

TIMBER DISTORTIONS Bow – Curvature formed in the direction of length Spring – Curvature formed in the direction of the edge of the timber. Cup – Curvature formed in the transverse direction of the timber forming a cup shape along the end. Twist – Spiral distortion along the length.

SEASONING DEFECTS Case hardening - early drying and shrinkage of exposed surface. Case hardening - early drying and shrinkage of exposed surface. Check – Crack separating the fibers of the wood. Check – Crack separating the fibers of the wood. Collapse – Flattening of wood due to uneven shrinkage. Collapse – Flattening of wood due to uneven shrinkage. Hone –combing – Radial and circular cracks formed in the interior portions Hone –combing – Radial and circular cracks formed in the interior portions

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