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REPAINT, REPAINT AND THIN NO MORE!

or Classification of coatings and Summary of coating recommendations

By Jean Tétreault

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Classification of Coatings by Film-forming Mechanism

Class

Solvent evaporation (SE):
Coalescence (C):
Oxidative polymerization (OP):
Moisture-cured polymerization (MC):
Catalysed polymerization (CP):
Change-of-phase (CoP):

Examples

shellac, cellulose nitrate
emulsion, latex, water-based
oil, alkyd, epoxy ester, oil-modified urethane
moisture-cured urethane
two-part epoxy, two-part urethane
powder coatings

Summary of the Coating Recommendations

Wood productsDP
MetalDP
Cementitious subst.DP
Airtight enclosures

(AE 1/day)
epoxy CP, CP+C:4 weeks
urethane CP *:4 weeks
all films C *, ‡:4 weeks
shellac SE •:4 weeks
all films CoP:1 day
epoxy CP, CP+C:4 weeks
urethane CP *:4 weeks
acrylic C:4 weeks
epoxy CP, CP + C:4 weeks
urethane CP *:4 weeks
all films C *:4 weeks
Leaky enclosures$

(AE 10/day)

epoxy CP, CP+C:2-4 weeks
urethane CP*, MC:2-4 weeks
shellac SE•:2-4 weeks
all films C*,•:2-4 weeks
all films CoP:1 day
baked alkyd OP:2-4 weeks
epoxy CP, CP+C:2-4 weeks
urethane CP*:2-4 weeks
acrylic C:2-4 weeks
epoxy CP, CP+C:2-4 weeks
urethane CP*,MC:2-4 weeks
all films C*:2-4 weeks
Open enclosures

(AE100/day)

epoxy CP, CP+C:4 days
urethane CP, MC:4 days
all films SE, C*:4 days
all films CoP:1 day
baked alkyd OP:4 days
epoxy CP, CP+C:4 days
urethane CP:4 days
acrylic C:4 days
epoxy CP, CP+C:4 days
urethane CP, MC:4 days
all films C*:4 days
Floors

(AE 100/day)
urethane CP, MC, C:4 days
epoxy CP, CP+C:4 days
acrylic-urethane C:4 days
all films CoP:1 day
baked alkyd OP:4 days
urethane CP:4 days
epoxy CP, CP+C4 days
urethane CP, MC, C:4 days
epoxy CP, CP+C:4 days
acrylic-urethane C:4 days
Contact between
objects and film
interleaves:4 days
all films*:4 weeks
interleaves:4 days
all films CoP:1 day
baked alkyd OP:2 weeks
unbaked films*:4 weeks
interleaves:4 days
all films*:4 weeks
Legend and notes:
DP:   drying period *:   should not have components formed by oxidative polymerization
AE:   air exchange rate ‡:   high amount of calcium carbonate is preferable
•:   varnishes need more layers $:   drying period will vary depending on the ratio
      of the coated surface to the volume of the enclosure.


For more information on the use of coatings for museum purposes, refer to:

Tétreault, J., "Coatings for Display and Storage in Museums", CCI Technical Bulletin no. 21. Canadian Conservation Institute. Ottawa (1999) 46 pp.


Canadian Conservation Institute, 1030 Innes Rd, Ottawa, Ontario, K1A 0M5, Canada
Web: http://www.cci-icc.gc.ca/

This text is published with the permission of the author.

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IAQ in Museums and Archives, 1999