Specific Gravities
| GRAMS PER CUBIC CENTIMETRE (Approximate) |
||||
|---|---|---|---|---|
| Wax | 1.0 | 14ct White | 14.9 | |
| Brass (67/33) | 8.5 | 18ct Yellow | 15.7 | |
| Copper | 8.96 | 18ct White (casting) | 16.4 | |
| Sterling | 10.3 | 18ct White (wire) | 16.9 | |
| Fine Silver | 10.5 | 22ct Yellow | 17.8 | |
| 9ct Yellow/Red | 11.4 | Fine Gold | 19.3 | |
| 9ct White | 12.6 | 95% Platinum | 20.6 | |
| 10ct Yellow | 12.2 | Pure Platinum | 21.4 | |
| 14ct Yellow | 14.1 | Pure Palladium | 12.0 | |
Conversion Chart:
Grams and Troy Ounces
1OZ = 31.1035 GMS
1GM = 0.03215 OZS
EG.
1KG = 1000GMS = 32.15 OZS
5OZ = 155.52 GMS
Commonly Used Formulae:
To find the weight of plate or wire:
Plate or Square Wire
Formula: Length x width x thickness x specific gravity
Example: 18ct Yellow Plate 50mm x 30mm x 1.2mm
= 5 x 3 x 0.12 x 15.7 = 28.26gr
Round Wire
Formula: Radius x Radius x 3.142 x length x specific gravity
Example: 18ct Yellow Wire 1.0mm diameter 500mm long
= 0.05 x 0.05 x 3.142 x 50 x 15.7 = 6.18 gr
To convert the known weight of an article from one alloy to another alloy
Formula: SG (specific gravity) of alloy required divided by SG of CT now x weight now = weight in new alloy.
Example: A 3gr 9ct ring - what will it weigh in 18ct?
= 15.7 div by 11.4 x 3 = 4.1gr
To find a length at a finished thickness - plate & square wire.
Formula: Thickness now div by finished thickness x length now = finished length
Example: Sterling plate 3.8mm thickness 50mm long - what will length be when rolled to 1.0mm? =0.38 div by 0.1 x 5 = 19cm Note: gains in width reduce gains in length.
To find the circumference of a circle: circumference = 3.142 x diameter
To find the area of a circle: area = 3.142 x (radius x radius)
To find volume of a cylinder: volume = 3.142 x (radius x radius) x height
NB: All measurements are converted to centimeters i.e. 3.0mm becomes 0.3cm.