Historic Artifacts

Updated October 26, 2011

Melting Points
75-265°C (167-509°F) - Plastic
135-177°C (275-350°F) - Solder (tin-alloy)
232°C (449°F) - Tin
300-400°C (572-752°F) - Pot Metal (copper-lead alloy)
300-400°C (572-752°F) -White pot metal
327°C (621°F) - Lead
375°C (707°F) - Zinc
593-1427°C (1100-2600°F) - Glass
600-1000°C (1112 – 1832°F) - Unrefined Earthenware
660°C (1220°F) - Aluminum
932°C (1710°F) - Brass (yellow)
960°C (1760°F)- Silver
1000-1200°C (1832-2192°F) - Stoneware
1063°C (1945°F) - Gold
1082°C (1981°F) - Copper
1200-1600°C (2192-2912°F) - Refined Earthenware
1350-1400°C (1920-2550°F) - Cast Iron
1427°C (2600°F) - Steel (stainless)
1455°C (2651°F) - Nickel
1516°C (2760°F) - Steel (carbon)
1535°C (2795°F) - Iron
1550°C (2822°F) - Porcelain
Thermal Alteration of Metals	
 Traylor (1990) refers to anecdotal accounts of automotive steel undergoing thermal deformation during severe wildland fire.  In addition, Sayler et al. (1989) observed the partial melting and deformation of lead during prescribed burns in mixed grass prairie fuels.  Metals common to the archaeological record such as iron, steel, tin, brass, copper, and lead do have established melting points at which significant damage could be predicted given sufficient fire intensity and energy output.  The established melting points for these metals are as follows: iron (1275-1535°C), steel (1250-1480°C), tin (232°C), brass (900-930°C), copper (1083°C), lead (327°C) (Perry and Green 1984).  Based on this information, tin and lead artifacts will likely be the most susceptible to melting during natural fire, other metals with higher melting points could be significantly affected only under conditions of severe fire intensity.
Archaeological metals, are of course, generally in a corrosive state in which electrochemical processes and ions create chemical compounds that adhere and bond to metal surfaces, and over time, may penetrate deep within the structure of metal objects  (e.g., rust) (Hoff 1970; Organ 1976; Waite 1976).  The extent to which exposure to fire affects corroded metal is not well documented; however, Engle and Weir (1998; 2000) have demonstrated that breaking strength, elongation, and ductility of new and corroded barbed wire is not significantly affected by exposure to grass fire.  Schiffer (1987) suggests that corrosion on metal surfaces can serve as a protective film in archaeological contexts.  Of particular interest, Schiffer also notes that if the coefficients of thermal expansion of the corrosive file and the metal are significantly different, thermal cycling could initiate cracking that could result in perpetuation of corrosion within the metal object.  It is possible the archaeological metals subject to natural fire conditions could be affected heat-induced cracking and subsequent internal corrosion.  In sum, then, archaeological metals subjected to wildland fire may be impacted by natural fire immediately due to melting and deformation, and over-time due to the potential increased internal corrosion. 

        Cans from late nineteenth and twentieth century sites are made from rolled, tinned steel. Fire may damage labels, melt solder on the older “hole-in-cap” cans, and burn off the tinned surface. However, can morphology (size, shape) which is usually the key to identification is unlikely to be affected by fire (Haecker n.d.).

Glass consists of three primary elements, silica, soda or potash, and lime or magnesia (Goffer 1980).  The formation of glass is accomplished through fusion and cooling of its major constituents (Goffer 1980; Havlác 1983).  The established melting point of glass is 750-870°C.  Glass is essentially a supercooled liquid that performs as a solid, and is therefore, subject to thermal stress (DeHann 1997).  Thermal stress caused by uneven heating will induce fracturing of glass when internal stresses exceed the tensile strength limit of glass (DeHann 1997; Lentini 1992).  Thermally altered glass may exhibit straight fracture lines, crazing, shattering, and melting depending on fire conditions (DeHann 1997).  As such, archaeological glass will be highly susceptible to thermal alteration under natural fire conditions given that the heat energy released by the fire is sufficient to induce significant thermal stress and/or melting.   



Ahler, S. A., Picha, P. R., Sayler, R. D., and Seabloom, R. W., Effects of Prairie Fire on Selected Artifact Classes. Annual Meeting of the Society for American Archaeology, 1990.  

Ayers, J. A., 1989. Post-fire Assessment of Historic Sites, Yellowstone National Park, 1988. Rocky Mountain Regional Office, National Park Service, Denver.  

Bayer, C., 1979. The Chalone Creek/South Pinnacles Prescribed Burn, Initial Archaeological Investigations.  

Hemry, L., 1995. Appendix 3. Green Basin: Studying the Effects of Springtime Burns on Cultural Material. In: Hemry, L., Timmons, R., Hvizdak, R., Webster, C., Thoms, A., and White, M., (Eds.), A Management Strategy and Study of Prescribed Burning Impacts on Heritage Resources in Ponderosa Pine/Douglas-fir Composition Types on the Kootenai National Forest, Northwestern Montana. USDA Forest Service, Northern Region, pp. 1-10. 

Kelly, R. E., To Burn or Not to Burn: The Challenge of Cultural Resources. Kings River Community College, 'Introduction to Fire Effects Class,' Reedly, CA, 1987, pp. 1-6.  

Pidanick, B., 1982. Prescribed fire/Cultural artifacts, investigating the effects. Pacific/Southwest Log October, 4-5. 

Powell, D. W., Wildfire effects on cultural resource sites and their management. Northwest Anthropological Conference, 1987.  

Sayler, R. D., Seabloom, R. W., and Ahler, S. H., 1989. Impacts of prescribed burning on archaeological and biological resources of the Knife River Indian Villages NHS. Prepared by the Institute for Ecological Studies, Department of Biology and Department of Anthropology, University of North Dakota. Submitted to the University of Wyoming National Park Service Research Center, Laramie Wyoming., Grand Forks, pp. 1-125.  

Timmons, R. S., 1999. Fire effects on prehistoric artifacts: Northern Region/Intermountain Research Station experiments preliminary research design for assessing site impacts, pp. 8 pp.  

Traylor, D., Hubbel, L., Wood, N., and Fiedler, B., 1990. The La Mesa Fire Study: An investigation of fire and fire suppression impact on cultural resources in Bandelier National Monument. National Park Service, Division of Anthropology, Branch of Cultural Resource Management, Santa Fe.  

Welch, P., and Gonzales, T., 1982. Research design, prescribed burn impact, evaluation upon cultural resources, LMDA and Thing Mountain Chaparral Management Projects. USDA Forest Service, Cleveland National Forest, pp. 1-9.  


Constructed with much sweat by Linn Gassaway.

Remember conditions are not static so Not making a decision is a decision.

Be safe No archaeological site is worth a life.  

This page is still under construction so please check back for additional information.

Website last updated October 26, 2011