become immediately apparent after the glue has been applied and
the joint brought together—a moment when the unforeseen tends to
occur. Contingency measures should be planned beforehand. It is impor-
tant to rehearse the procedure “dry” (without glue) up to the stage of
pressure application.
It is also important to consider how well a painting’s condition can
accommodate the rejoining procedure. Relevant factors are the condition
of the ground and paint layers, whether the layers tend toward flaking,
thesolubility and reactivity of the adhesive and its components, and the
wood’s strength and degree of warp. Weak, porous, water-based animal-
glue grounds, for example, might distort or flake during manipulation.^4
Apanel can sometimes be pressured into alignment, but inherent
weaknesses could initiate further splits immediately or in the future. The
type of panel wood is an important factor. The more flexible woods, such
as poplar, may accommodate greater distortions from pressure without
failing.^5 Accepting less than perfect alignment may be the best alternative
if further treatment might overstress the panel and painting.^6
Gluing procedure varies from case to case. Generally, old glue is
thoroughly cleaned from complete disjoins, which are then aligned and
separated slightly. After glue is applied to both joint faces, the joint is
pressed together with relatively low pressure. For more highly concen-
trated glues, the glue line may be thinned by “rubbing” (slightly moving
one joint face back and forth against the other by hand or by small
repeated turns of the clamps used to apply out-of-plane alignment pres-
sure). One cannot usuallyproduce a true “rubbed joint” because the joint
edges would probably cease to move at a moment when the panel is in
the wrong position. However, short of this, a thinner glue line—desirable
for durability and a better match to the original joint—can be achieved.
As splits must be positioned with greater care, rubbing is normally not
possible. For splits, the closest joint is achieved by fitting the torn wood
together exactly.
It is not necessary to replane joint faces to eliminate gaps, though
some panels have beenso treated. Inserts or gap fillers can be used instead.
A replaned joint may be suspected ifthe image no longer registers where
it crosses the joint. To identify and then treat this condition effectively, it is
best—prior to structural work—to remove the varnish, retouchings, and
putties that obscure the joint.
Where joint gaps do occur, fillers may be employed; these may be
wooden inserts or part of the adhesive system. If there is an excessive gap
and wooden inserts can be fitted effectively without the removal of origi-
nal wood, they are the preferred choice because they use a thin glue line,
which increases durability. Thinner glue lines are more flexibleand there-
fore able to move with the surrounding wood. In contrast, a glue-saturated
filling compound is more likely to force the surrounding panel to comply
under stresses.
Rejoining and gap filling of joints must be considered in conjunc-
tion with preservation of the original panel wood. Some conservators pre-
fer to replace the original wood with wooden inserts, usually V-shaped in
section, whose good fit should result in a more complete and thinner bond
line than that achieved by rejoining the original wood unaltered. The
joints (for two new joints are created) can be made as sound as technical
skill, patience, and materials will allow. Again, because the glue line can420 Brewer