The Structural Conservation of Panel Paintings

is calculated. Approximately 20% of this volume is oxygen that can be

scavenged by the insertion of an appropriate number of Ageless packets;

however, it is recommended that double the calculated number of Ageless

packets be inserted into the bag to provide a large margin of safety

(Fig. 3). The unsealed opening is then heat-sealed and left for fourteen

days (Figs. 4, 5). As the reaction of Ageless with oxygen is exothermic, the

Ageless packets can become hot. It is, therefore, important that the pack-

ets not be placed on the painting’s surface. The heat generated by the reac-

tion is localized; in experiments, the temperature and RH within the bag

remained constant.

Dynamic and dynamic-static systems

Both the dynamic and the dynamic-static systems use nitrogen gas sup-

plied by apressurized tank or nitrogen cylinder. The nitrogen gas is passed

through a series of polypropylene tubes and delivered to the encapsulating

bag, where it replaces the oxygen in the bag (Fig. 6). In this way the oxy-

gen concentration in the bag is reduced to 0.1%. These two methods were

developed for the treatment of larger objects (Hanlon et al. 1992; Daniel et

al. 1993; Daniel, Hanlon, and Maekawa 1993). Both methods initially use

the same procedure offlushing the bag with a high flowofnitrogen gas.

As nitrogen gas that comes directly from a gas cylinder has a very low RH,

it is essential to introduce a humidification system between the nitrogen

M A T  I I 73

Figure 3
Placing oxygen-scavenger sachets into the
encapsulating bag through the unsealed open-
ing at the end ofthe bag.

Figure 4, below
Final heat-sealing ofthe opening used to
insert the oxygen-scavenger sachets into
the bag.

Figure 5, below right
Finished bag enclosing the panel painting
tobe treated and the number of oxygen-
scavenger sachets calculated to reduce the
oxygen concentration to 0.1%.