Preservative Protection

No timber is totally immune to deterioration if it is exposed, over a sufficient period of time, to one or more of the agents responsible for timber degrade.

The main agents of timber degrade are

• fungi
• insects
• marine borers
• Fire and weathering

For any one of these agents to affect timber, certain criteria are necessary and the elimination of one or more of these requirements will inhibit the start of timber degrade. Wood protection involves removal or control of one or more of these requirements by the introduction of various chemicals to the timber.

The principle criteria used in evaluating a wood preservative are:

– Efficacy

– Permanence

– Penetration

– Non-corrosive to metals

– Non-damaging to wood

– Safe handling

– Odourless

– Colourless or coloured

– Does not affect moisture content

– Can be painted and glued

– Does not increase fire hazard

– Environmental acceptability

– Cost

Wood Preservation Processes

All the wood preservation processes in current use can be placed under one of the following categories:

1. Non Pressure Process: Brushing or spraying, dipping

2. Pressure Process:

   – Low pressure process: double vacuum

   – High pressure