Series editors' preface - Wood Tools

456 Conservation of Furniture
Figure 10.10 Home-made hollow drill for removing
nails
through gunsmithing catalogues), may be used
for this purpose. The second method requires a
hollow drill fashioned from a piece of brass or
silver steel of a suitable diameter. The centre is
drilled out to a depth of about 25 mm and teeth
are filed into the end (Figure 10.10). If the drill
bit was made from silver steel, it is then
tempered ‘by the colours’. The surface is
polished and the tool slowly heated from the
non-tooled end. The temper colours (light
straw through to blue) travel along the length
and when the light straw colour reaches the
saw teeth the tool is plunged again. Once cool,
the saw teeth can be filed sharp. Information
on hardening and tempering home made tools
can be found in Weygers (1973). Proprietary
hollow drills are manufactured by Holzer. A
carving gouge is used to mark a circle around
the nail to provide a secure start position for the
drill bit. The drill should be withdrawn and
waste cleared regularly and this can provide an
opportunity to see if the nail can be removed.
Nails have often been used in a range of illconceived
places. It may be possible to saw
through the nail with a hacksaw to allow the
components to be separated before removing
the nail itself. If the space is narrow, a hacksaw
blade may be used without the saw frame.
Removing the set of the teeth, by working the
hacksaw flat on an oilstone, will prevent
damage to the wood. The small circular saw
blades used with a flexible shaft machine or a
Dremel tool are very thin and may also be
useful in this context. If a nail head is punched
through from underneath the upper surface
should be held firmly against a scrap piece of
softwood to prevent breakout of the surrounding
wood. Rivets holding metal brackets may
be removed by drilling out the rivet heads to
allow removal of the bracket. A flexible shaft
machine with a burr or stone is often useful.
Shanks may be removed in the same way as
described for nails.
Once the joint has been cleared of obstructions
it can be taken apart. If it is very loose a
few blows by the joint with a white rubber
mallet may suffice to separate the components.
If a wooden or dark rubber mallet is used the
surface of the component should always be
protected from damage by a scrap piece of
wood. Care should be taken that the force of
the blow is directed through the joint and is
not transmitted to thin or fragile components.
Whenever force is applied to separate a joint,
it should be directed so that the original geometry
of the joint is maintained.
On occasion it is necessary to dismantle a
joint that is sound in order to gain access to
another that has been damaged or is loose.
Joints that have been adhered with animal/hide
glue may be loosened by injecting a small
amount of water, isopropanol or ethanol
through a pre-drilled hole into the joint to
break the adhesive bond. Isopropanol is particularly
effective. In some cases water injected
into the joint may cause animal/hide glue and
joint components to swell and may thus hinder
rather than help dismantling the joint. It may
be more effective to combine both heat and
water by using a small steaming device, such
as tubing with an attached syringe coupled to
a pressure cooker (Rodd, 1976). Care must be
taken to ensure that isopropanol or ethanol do
not come into contact with the surface finish,
which they are likely to damage. Some conservators
have successfully experimented with
portable radio frequency heating units. A small
amount of water is injected from a syringe into
the joint through a pre-drilled hole. The RF unit
excites and heats the water, dissolving the glue
and allowing the joint to be dismantled (Neher,
1996).
It may be possible to use wooden wedges to
force a mortise and tenon joint apart. Such
wedges should be wide and made from softwood
to prevent crushing or bruising the