# 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

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.