Common woods compared; how to deal with decay and woodworm.

1 Preamble

People who are interested in tools tend to be either users or collectors.

Tool users are those who use tools to earn a living, or as a hobby; they will repair or modify tools in order to gain maximum utility. Tool collectors collect out of interest, but often do not wish to use them. This group generally prefer tools to be in original condition, and find repairs undesirable and modification anathema.

With these different values, users and collectors seldom agree on the best ways to deal with collectable tools. I have personally been a user longer than a collector, so my opinions may be orientated in that direction.

2 Properties and characteristics of woods used in tool making

2.1 Hardness

Is the resistance to deformation and wear:

Hard - ash, beech, birch, hornbeam, maple, oak.
Very hard – boxwood, hickory, rosewood.
Extremely hard – ebony, lignum vitae.

2.2 Toughness

Is the ability to withstand shock and loads:

Very tough – ash and hickory.

2.3 Durabilty

Is the natural resistance to insect and fungal attack:

Very vulnerable (perishable) – ash, beech, birch, and the sapwood of almost all species.
Vulnerable (non durable) – hickory, maple.
Durable – boxwood, mahogany, oak.
Very durable – ebony, rosewood.

2.4 Permeability

Is the ease with which wood can be impregnated with liquid eg water (or preservatives, to increase durability:

Permeable – beech, birch, hornbeam.
Moderately resistant – ash, hickory, maple
Resistant – boxwood
Extremely resistant – ebony, mahogany, oak, rosewood

2.5 Movement

This relates to the extent that dried (seasoned) wood will undergo dimensional change due to changes in ambient humidity. The following is based on a change from 60% to 90% relative humidity:


Small movement (under 3%) – rosewood.
Medium movement (3 to 4.5%) – ash.
Large movement (over 4.5%) – beech.

It hardly needs saying that it is highly desirable to keep wooden items in a dry and stable environment.

3 Modes of deterioration; prevention and treatment

3.1 Fungal attack

Wood rotting fungi can only survive in wood with a moisture content above 20%. If infected wood is then dried to below this level, the fungi will dry out and further attack be stopped. However, spores may survive and become active should the wood once again become damp. It is therefore advisable to treat such wood, when dry, with one of the proprietary treatments eg xxxxx. "Instructions on the tin" should be followed; essentially, the infected section needs to be soaked in the fluid.

In a heated building, the moisture content of wood usually stabilises out below 14%.

3.2 Insect attack (ie woodworm)

There are many species of wood boring insects and most die out when the wood is dried. However, the so called "common furniture beetle" (Anobium Punctatum) does attack dry wood. It will attack the sapwood of most species and the heartwood of many. Beech is especially susceptible to this pest. Normally immune are boxwood, ebony, and rosewood.

Both fungal and insect attack are easily treated and preventable; but the damage caused is not so easily repaired.

Woodworm is a particular pest in beech planes; but the following remarks apply to any attacked item where the flight holes are an indicator.

A flight hole is simply evidence that a beetle has emerged and flown away. The cycle followed is:

  • Beetle flies in.
  • Lays eggs.
  • Eggs hatch to become larvae
  • Larvae tunnel through wood
  • Larvae hatch into beetles, emerge, and fly away; possibly to return and repeat the cycle.

Flight holes do not therefore tell us if the infection is current, or has died out long ago. Nor does the absence of flight holes necessarily mean that the plane is free from infestation since the larvae tunnel within the wood for up to three years before emerging as beetles. As I have no way of knowing whether the plane is infested or not, I always treat beech-wood planes with preservative so as to kill off any possible infestation and impart long-term protection.

3.3 treatment for insect attack

The principle of wood preservation is to provide an "envelope of protection" ie impregnating a surrounding envelope of preservative (insecticide and fungicide), the deeper the better, so as to present a barrier to any insect seeking to penetrate.

For small wooden items (I consider even a large try plane to be small) soaking in a clear organic-based solvent-based preservative* for about 40 minutes will achieve a penetration of about 4mm on the radial and tangential surfaces and up to 40 mm through the end grain. (I tend to use xxxxxx but any clear organic solvent-based preservative will suffice).

Applying treatments with a brush will not achieve deep penetration, nor will injecting flight holes. Water-based preservatives are to be avoided as they will cause wood to swell, raise grain, and ferrous components to rust. Whilst solvent-based preservatives have an unpleasant smell which lingers for several days, they do not cause swelling or rust. All the preservatives available to the public are safe to use provided the safety and disposal instructions on the tin are followed.

An alternative treatment for killing suspected larvae is to keep the item in a deep freeze for about 7 days. This will not, however, provide any protection against future attack.

Whilst there is no preservative reason for filling flight holes, it is advisable as it allows fresh holes to be readily detected. Suitable fillers are coloured waxes or polishes (Axminster Tools supply a range).

An important routine is to mark your calendar with a reminder to check all wooden tools following the period May to August, when the beetles emerge.

Woods used in Tool Making
Ref No:  MN03.01
Date:  10-09-2013
Author: Gerald Farnworth
Suggestions for improvement are welcomed, please email: conservation@taths.org.uk
IMPORTANT: The advice in these notes is provided by members and others. It is given in good faith but neither the contributors nor the Society can endorse or guarantee the accuracy or safety of the information. The society does not recommend or guarantee any individual or organisation named.

Treatment techniques described may not be suitable for items of high or historical value. Users should always test first on a small inconspicuous area; observe safety and health guidelines given by suppliers, and dispose of used materials responsibly. The Society does not endorse or guarantee any proprietary products named (and it recognises that other products may be suitable). If in any doubt, expert advice should be obtained.

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