About Bi-Metal

(Images courtesy of Barbara Terrell and Sydney Lynch.)

18K & 22K Yellow on Sterling Silver Bi-Metal

DESCRIPTION AND USE

A layer of 18 karat gold alloy with a rich yellow color or 22 karat gold alloy with a bright yellow color is bonded with sterling silver to form a sheet of precious metal with two distinct surfaces. The 18K gold layer is similar to that of most gold filled products while the 22K is two to three times thicker than gold filled products giving it more workability. Surface treatments, such as engraving, scraping, folding, and twisting, can be used to accent the two surfaces.

COMPOSITION

	18K		22K
By weight:	5.00% 18 karat gold		12.50% 22 karat gold
	95.00% sterling silver		87.50% sterling silver
By volume:	3.38% 18 karat gold		7.63% 22 karat gold
	96.62% sterling silver		92.36% sterling silver
24 gauge:	.00068" thick 18 karat layer	24 gauge:	.001534" thick 22 karat layer
	.01942" thick sterling layer		.018565" thick sterling layer
20 gauge:	.001082" thick 18 karat layer	18 gauge:	.003076" thick 22 karat layer
	.030918" thick sterling layer		.037223" thick sterling layer
26 gauge:	.00054" thick 18 karat layer
	.01546" thick sterling layer

MELTING POINT

18K:	Solidus: 1620 °F / 882 °C
	Liquidus: 1715 °F / 935 °C
22K:	Solidus: 1780 °F / 971 °C
	Liquidus 1840 °F / 1003 °C
Sterling:	Solidus: 1435 °F / 780 °C
	Liquidus: 1640 °F / 890 °C

Between 1600 °F and 1650 °F silver side will begin to flow and reticulate below the gold layer.

ANNEALING TEMPERATURE

1140 °F to 1300 °F

SOLDERING

On gold surface use: 14K or 18K yellow easy (soft) solder
On sterling surface use: easy or medium silver solder

DENSITY

	18K	22K
Specific gravity (GM per cubic CM):	10.53718	10.9367
Ounces per cubic inch:	5.5516	5.7621
Ounces per square inch:	20 gauge: .17765"	18 gauge: .23221"
	24 gauge: .11159"	24 gauge: .11583"
	26 gauge: .08883"

STOCK SIZES

Sheet and circles: 18K: 20 and 24 gauge - 22K: 18 and 24 gauge
Sheet: minimum 1" x 1" maximum 3" x 12"
Circles: 1/4" diameter to 2" diameter