Paper Conservation: Decisions & Compromises

cellulose powders with cellulose ethers to determine
appropriate types of cellulose powders that
spread smoothly and will not block the nozzle
during spray operation. Cellulose ethers have
been studied extensively for their stability (Backer,
1984; Feller & Wilt, 1990). Three different
cellulose fibers with 0.2% methyl cellulose added
were selected for evaluation. The formula is described
as follows:
1. 0.5 g of Arbocel BC 1000 fiber with 10 g of 0.2%
methyl cellulose.
2. 0.5 g of Arbocel BC 200 fiber with 10 g of 0.2%
methyl cellulose.
3. 0.5g of microcrystalline cellulose with 10 g of
0.2% methyl cellulose.
Fig. 2: Before and After Filling
air stream atomizes the liquid or paint into tiny
droplets as it blows past a very fine paint-metering
component. Various triggers are designed to
control the amount of liquid, allowing an operator
to achieve finely smooth blending effects.
Three factors affect the effects of the airbrush
technique – the spray distance, the air pressure
and the viscosity of the paint. Generally speaking,
the airbrush should be placed a distance of
10 to 20 cm from the object to be sprayed. Pressure
should be adjusted between 0.1Mpa to 0.2
Mpa in general, although it can be reduced to
0.02Mpa to 0.05Mpa in order to achieve fine, delicate
results. The ideal viscosity of the substance
used for spray purposes should be maintained
between 45 to 60 cp.
For the purposes of this study, three stages
were designed to evaluate the applicability of
airbrush techniques using cellulose powders for
filling purposes: (1) the type of cellulose powder;
(2) appropriate viscosity of the powder mixture;
and (3) the mixture for spray application.
Selecting cellulose powders
The first stage of this study involved mixing
A spray test showed that the microcrystalline
cellulose powder mixture sprayed smoothly with
no blocking effect, and it was the only type of
cellulose which could pass through the 0.1mm
diameter nozzle of the airbrush. The results
showed that microcrystalline cellulose was an
appropriate type of cellulose for further study as
a filler material.
Viscosity test
After the first stage, the microcrystalline cellulose
powders were then mixed with cellulose
ethers and gelatin. Six groups of mixtures, all
containing methyl cellulose (MC), carboxymethyl
cellulose (CMC), microcrystalline cellulose (MCC),
water and ethanol, were divided into two major
subgroups depending whether or not gelatin was
added. Among the ingredients, ethanol was used
to increase mobility and to speed up the drying
rate. Gelatin is used as a sizing agent and as dispersing
agent in the paper industry. The formulations
and ratio by weight are shown as follows
and in Table 1.
A: 2%MC, MCC, water, ethanol
B: 2%CMC, MCC, water, ethanol
C: 2%MC, 2%CMC, MCC, water, ethanol
D: 2%MC, MCC, water, 2%gelatin, ethanol 99%
E: 2%CMC, MCC, water, 2%gelatin, ethanol 99%
F: 2%MC, 2%CMC, MCC, water, 2%gelatin, ethanol
99%
Measurement of viscosity was then carried out
in order to adjust the viscosity of mixtures to
between 40 to 60 cp, which will yield better
consistency for spraying effects. A viscosity cup
was used for measurements. Drain time for this
test was suggested as between 17 to 23 seconds
ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013
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