DT 1.2

• In what direction do wood fibres grow along?

  The length of the tree or branch
• What do wood fibres consist of?

  Hollow cells (tracheids) supported by lignin resin.
• What part of the timber is strongest and which is weakest?

  Timber is strong in the direction of the grain (along the grain) and weaker across the grain
• What are the two types of seasoning?

  Air seasoning

  Kiln seasoning
• How does air seasoning work?

  Involves stacking the wood under a shelter, protected from the rain.

  Air circulates between the planks to slowly remove the excess moisture
• Air seasoned wood is used for what type of products and why?

  Air-seasoned wood is used for outdoor wooden products because it is seasoned to the same moisture content as its surroundings and therefore the wood will be less prone to defects.
• How does kiln seasoning work?

  A more expensive but controlled method which is very quick and can take just a few weeks.

  Planks are stacked onto trolleys and placed in the kiln where both temperature and humidity are controlled. Initially, the kiln atmosphere is very steamy but this is graduallly changed to become hotter and drier.
• Kiln-dried timber is used for what type of products and why?

  Indoor products such as furniture will use kiln-seasoned wood because it has been seasoned to meet indoor conditions and will have a lower moisture content than air-dried wood.
• What happens is an unseasonaed plank is placed in a heated room?

  It will twist, warp, cup or bow when drying out and cracks or gaps may appear.
• Seasoning the wood gives what advantages?

  Greater immunity from decay and increased resistance to rot

  Increased strength and stability

  Helps preservatives to penetrate

  Makes wood less corrosive to metals
• When ordering wood, how do designers lab it to show how it has been seasoned?

  Oak air-dried (A-D) : suitable for exterior use

  Oak kiln-dried (K-D) : suitable for interior use
• When does wood shrink and expand?

  It expands and shrinks with changes in humidity (the amount of water present in the atmosphere ).
• How d you reduce the time taken to season wood to the correct moisture content ?

  Trees should be felled in the winter when they grow less, have less sap and therefore contain least moisture.

  The largest amount of shrinkage occurs after the tree is cut down and while it is being seasoned.
• In which direction does wood shrink ?

  Almost no shrinkage in the direction of the wood’s grain (lengthwise).

  Some shrinkage happens radially (perpendicular to the growth rings), with a greater amount of shrinkage occurring tangentially (along the curvature of the growth rings).
• What part of the wood loose the most moisture quickest?

  The ends of the wood tend to lose moisture content more quickly than the core.

  Sometimes cracks can appear in the plank ends.
• Why must care be taken when seasoning the wood?

  So that the whole plank will shrink uniformly and usually once the wood has been fully seasoned, any cracks will close as the plank is now in equilibrium throughout.
• Why can seasoned wood be susceptible to shrinkage in a house ?

  Seasonal changes in ambient humidity but this is less of a concern in modern homes where temperatures are fairly constant due to heating and air conditioning systems.
• What are the hardwoods?

  Oak

  Ash

  Mahogany

  Teak

  Birch

  Beech
• What are the softwoods?

  Pine (European redwood)

  Spruce

  Douglas fir

  Larch

  Cedar
• What are the manufactured boards?

  Plywood

  Marine plywood

  Aeroply

  Flexible plywood

  Chipboard

  MDF
• What are the properties and characteristic of oak?

  Hard

  Tough

  Attractive grain

  Good weather resistance

  Contains tannic acid which will corrode steel screws or fixings
• What are the properties and characteristic of ash?

  Tough

  Attractive open grain pattern which makes it more flexible
• What are the properties and characteristics of mahogany?

  Can contain interlocking grain, making it more difficult to work

  Rich dark red colour
• What are the properties and characteristics of teak?

  Hard

  Tough

  Straight grain

  Natural oils resist moisture

  Acids and alkalis
• What are the properties and characteristics of birch?

  Hard

  Straight closed grain

  Resists warping
• What are the properties and characteristics of beech?

  Tough

  Closed grain

  Hard

  Available in steamed (white colour) and unsteamed (pink tinge)

  Does not impart a taste to good
• What are the properties and characteristics of pine ?

  Straight grain

  Knotty

  Can contain resinous knots
• What are the properties and characteristics of spruce?

  Straight grain

  Resistant to splitting
• What are the properties and characteristics of douglas fir?

  Straight or slightly wavy grain

  Few knots

  Stable

  Good resistance to corrosion
• What are the properties and characteristics of larch?

  Hard

  Tough

  Attractive grain patter fades to silver upon exposure outside

  Good resistance to moisture
• What are the properties and characteristics of cedar?

  Straight grain

  Con corrode ferrous metals due to acidic nature

  Low density

  Good sound damping

  Good resistance to moisture
• What are the properties and characteristics of plywood?

  Thin layers of wood are placed and glued at 90 degrees to each other and compressed to form the board.

  Good strength in all directions

  No grain weakness

  Always has an odd number of layers
• What are the properties and characteristics of marine plywood?

  Similar construction of plywood but is gap and void free and uses special set water and boil proof glue to provide resistance to moisture

  Some higher quality marine plywood is also resistant to fungal attack
• What are the properties and characteristics of Aeroply?

  Plywood made from high quality timer such as birch

  Available in very thin sheets

  Lightweight

  Each to bend around a support frame
• What are the properties and characteristics of flexible plywood?

  An odd number of layers glued together with two out layers made from open grained timer which allow the sheet to flex

  Bent and glued around a former to achieve a solid shape
• What are the properties and characteristics of chipboard?

  Wood chips compressed with a resin such as urea formaldehyde
• What are the properties and characteristics of MDF?

  Compressed wood fibres although sometimes urea formaldehyde is added as an additional resin

  Two smooth surfaces

  Available in other standard grade or veneered with a layer of timer
• What are the properties and characteristics of of veneers?

  Thin slices of wood less than 3mm thick
• What are the properties and characteristics of MF laminates?

  Thin sheets of MF polymer

  Hard

  Tough

  Chemical resistant
• What are the uses of oak?

  Furniture

  Flooring