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© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
PowerPoint Timber
Unit 215: Preparing surfaces for decoration
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Learning outcomes • Know how to prepare timbers and timber sheet products ready to
receive finishing systems.
• Be able to prepare timbers and timber sheet products ready to receive finishing systems.
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Timber classification
Timbers are identified as softwood and hardwood, according to their characteristics.
Task
In groups identify two softwood and hardwood trees.
Softwood Hardwood Faster growing Slow growing
Evergreen Deciduous
Needles instead of leaves Broad leaves
Shorter roots Longer roots
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Hardwood and softwood trees Softwood Hardwood
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Softwoods
• Evergreens are easier to cut than hardwood trees, which are denser.
• However, there is no minimum weight requirement to become a hardwood (eg balsa wood).
Types of trees • Conifer • Fir • Cedar • Pine Uses Door frames, architraves and frames, low budget furniture, stud partitions etc.
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Hardwoods
• Most are deciduous (their leaves are large, broad and fall off each autumn, growing back again in the spring).
• Not always harder than softwood.
Types of trees
• Oak
• Elm
• Beech
• Mahogany
Uses
Furniture making, floors and exterior doors (usually varnished, oiled or stained).
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Properties of timber Task
In groups describe the following properties of timber:
• Porosity
• Adhesion
• Capillaries
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Moisture content Task
Discuss in groups what moisture is and how it can affect timber.
• Wood can hold large amounts of water because it is made up of cells.
• Seasoned timber should contain no excess moisture.
• Seasoned timber should not be exposed to any contact with water or moisture prior to any protective coating being applied.
• Heavy moisture can cause fungi or dry rot, reducing the weight and strength of the wood.
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Moisture content
Recommended amount of moisture in timber prior to painting
Not exceeding 21%
Process of the removal of moisture in timbers
Seasoning (by air or kiln)
• To check the amount of water, use an instrument called a moisture meter.
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Timber sheets/boards Timber is a sustainable material that can be recycled from its original source.
By re-manufacturing we can benefit from other properties such as:
• Improved strength
• Smooth surfaces
• A new waterproof product
• Increased ease of cutting
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Timber sheets/boards There are a variety of different timber boards, all with different uses and advantages.
• Plywood
• Oriental strand board (OSB)
• Medium density fibre board (MDF)
• Chipboard
• Blockboard
• Hardboard
Task
In groups describe the types of board (Activity 9).
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Timber is a natural organism, prone to defects.
Knots – most common defect: result of the branch in the tree.
• The knot may be live, sound, or tight. • Dead knots become loose and downgrade
the appearance and stability of the board • The more knots, the lower the quality of
the wood. Task
Knots require sealing prior to painting.
What would be the recommended coating for the defect: shellac knotting or aluminium wood primer?
Timber defects
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Timber defects End grain
Trees are felled and the timber is cut into planks leaving the end grain exposed – the most absorbent part of the timber.
What is the recommended treatment for end timber?
• Preservative, shellac, aluminium wood primer and oily primer.
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Timber defects Splits and cracks
Ruptures or separations in the grain of the wood which reduce quality as measured by appearance, strength or utility.
May be caused by:
• Excessive moisture
• Extreme machining
• Mechanical damage
• Growth stresses
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Questions
1. Identify one softwood and one hardwood timber and state their uses in construction.
2. What is the recommended amount of moisture content for timbers?
3. What is the term ascetics?
4. What method is used to remove moisture in timber?
© 2013 City and Guilds of London Institute. All rights reserved.
Level 2 Diploma in Painting and Decorating
Any questions?