Caulking (sealants)

Description

Any material used to fill or seal joints and openings. Ancient boats were found with fiber and wood fills, but later natural waterproofing materials, such as waxes and tars were also used. Oil-based caulking, or Putty, was composed primarily of Calcium carbonate or Lead white mixed with drying oils. Ntural rubbers and vulcanized rubbers also found there way into usage as sealants, adhesives and fills. The first elastomeric sealant, commercially developed in the 1950s, was composed of Polysulfide (Thiokol®). Butyl rubber sealants, also manufactured in the 50s, contained Talc, calcium carbonate, Polybutylene, Mineral spirits, and adhesion promoters. The first acrylic sealant, promoted in 1958, was a solvent curing product that included calcium carbonate, Silica, Solvent, and Plasticizer. Silicone sealants, introduced in the 1960s, are still the primary type that is used in museums for building display cases. These sealants often contain Fumed silica, calcium carbonate, ground Quartz, Carbon black, talc, and plasticizers. Polyurethane elastomers provide good abrasion resistance. Latex caulking, available in the late 1960s, eliminated the use of organic solvents. They typically contain a polymer emulsion (such as Polyvinyl acetate) in water with calcium carbonate, plasticizers, and other additives.

Caulk/putty	Earliest use	Composition	Examples	Applications	Characteristics and Risks
Fibers/Wood	ancient times			boats
Wax	ancient times			vessels	becomes soft with heat
Tar	ancient times			boats
Oil-based caulk (sometimes lead-based putty)	19th-20th c.	10-15% Linseed oil with Calcium carbonate, red or White lead and sometimes other inorganic fillers (Talc, Alum, Asbestos)		Seal window to frame, fill defects in wood and metal; surround pipe joint	Lead compounds accelerate drying; some components are toxic
Cement putty		Concrete		mortar
Gesso putty		Gelatin with Chalk
Rubber (natural, vulcanized)	19th c to WWII			gaskets, shock mounts,	waterproof, can crack due to ozone
Polysulfide	1950s	Any synthetic rubber vulcanized with sulfur (styrene-butadiene, Polyisoprene)	Neoprene, Thiokol	o-rings, pipe linings, building joints, and as sealants to fill joints in pavements, and glass/metal connections.	may release sulfur; may contain PCBs; poor tensile strength; abrade easily; replaced in 1980s by silicone and urethane sealants
Butyl rubber	1950s	Isobutylene-isoprene, Talc, Calcium carbonate, Mineral spirits, adhesion promoters		primarily used outdoors for metal and masonry joints that may expand and contract (gutters)	sticky and messy, but more resistant to sunlight than natural rubbers; combustible; paintable
Acrylic (solvent-based)	1958	solvent cured acrylic resin with Calcium carbonate, Silica, Solvent and plasticizers.
Silicone	1960s	Silicone resin cured with moisture or peroxides; may contain Fumed silica, Calcium carbonate, ground Quartz, Carbon black, Talc, plasticizers, Acetone, Methylene chloride.	Silastic, Clear Museum Gel	used around plumbing fixtures; to caulk joints in bathroom tiles; seal gap on exterior walls/roofs around pipes and wirings	water-repellent; long-life; wide temperature range; mold/mildew resistant; not paintable; poor adhesion; may release Acetic acid or Methanol on cure; may have residual curing compounds and silicone oils; may stain porous materials; some silicone caulks contain latex making them paintable but less durable
Polyurethane elastomers	Polyurethane cured with moisture, Calcium carbonate, Titanium dioxide, aromatic naphthas and petroleum distillates.		Vulkem	primarily used for sealing cracks and expansion joints in driveways and other outdoor concrete surfaces. It's also suitable for filling and repairing cracks in masonry-stucco walls.	very durable; abrasion resistant; flexible at low temperatures; combustible producing toxic fumes; may release acetic acid on curing, aging, or deterioration; susceptible to hydrolysis that may decrease adhesion
Vinyl latex	late 1960s	Vinyl (Polyvinyl acetate) with calcium carbonate, plasticizers	Reprosil	fill small gaps and blemishes in wood trim prior to painting	inexpensive; may be painted and used outdoors; may evolve trace Acetic acid as it cures
Acrylic latex		Butyl methacrylate, Calcium carbonate, water	Flugger	fill small gaps and blemishes in wood trim prior to painting	inexpensive, fast-drying, and paintable; minimal shrinkage; used indoors

Synonyms and Related Terms

caulking (noun); caulk (verb); calking; cauking (sp.); sealant; putty; spackle; Kitt (Deut.); Glaserkitt (Deut.); Fensterkitt (Deut.); kalfatring (Dan.)

Resources and Citations

• AIC Conservation Wiki: Caulk Sealants to Seal Exhibit Cases
• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
• ASTM, "Standard Terminology Relating to Paint, Varnish, Lacquer and Related Products", Annual Book of ASTM Standards, Section 6, Paints, Related Coatings and Aromatics, ASTM, D16, 7-Jan, Jul-96
• Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
• Ivan Myjer, contributed information, 1998
• Wikipedia: http://en.wikipedia.org/wiki/Caulking (Accessed Feb. 10, 2006)
• Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998