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
|