Organization: Precious Metal Arts
Marshall - heres the conversion charts. I hope these e-mail ok. If
you’d like a 2 page version on MS Word 7.0, let me know and I’ll send
one on over - this one looks like it may print a little long. BTW, I
don’t believe that the built up borax glass in crucibles does act as a
heat sink. It’s purpose is to prevent oxygen from entering the melt
from the pores of the crucible from underneath. The borax glass acts
to prevent this - coupled with a reducing flame, this is all intended
to prevent any O2 from entering your melt. Hope this helps, Mike
C O N V E R S I O N C H A R T S
Fineness of Gold Karats
Karat Fineness
9K .37500
91/2K .39583
10K .41666
13K .54166
14K .58333
17K .70833
18K .75000
21K .87500
22K .91666
24K 1.0000
Raising & Lowering Karat of Gold
Lowering Karat of Gold
A = G x (K - W)
W
A = Weight of Alloy Needed
G = Weight of Gold
W = Karat Wanted
K = Karat of Gold on hand
Raising Karat of Gold
FG = S x (KW - KS)
24K - KW
FG = Fine Gold
KS = Karat of Scrap
KW = Karat wanted
S = Weight of scrap
Gold & Silver Alloys
Fine Gold Fine Silver Copper
22K (.917) 1.000 .045 .046
18K (.750) 1.000 .213 .120
14K (.585) 1.000 .284 .426
SS (.925) 1.000 .081
18K Rose 75% 22.25% 2.75%
Metal Weight to Wax Weight Factor
Metal Factor
Platinum 22
22K 18
18K 18
14K 14
10-12K 12
Pure Silver 10.5
Sterling Silver 10
(DonAEt forget to add a minimum of 5 grams for your button! It never
hurts to have a big button!)
Weights & Measures
From To Multiply By
Caratsaaaa.DWTaaaa .12860
Grains (Troy)a.Gramsaaa… .0648
Grains (Troy)a.DWTaaaa .0417
Gramsaaaa.Caratsaaa… 5
Gramsaaaa.DWTaaaa .64301
Gramsaaaa.Oz (Troy)aa. .03215
Inchesaaaa.Millimetersaa 25.4
Ounces (Troy)aGramsaaaa 31.103
Ounces (Troy)aDWTaaaa. 20
DWTaaaa…Caratsaaaa 7.778
DWTaaaa…Gramsaaaa 1.5552
MM Width to Carat Weight
(approximate diamond weight)
Round Stones
1.5mm .01ct
1.7mm .02ct
2mm .03ct
2.2mm .04ct
2.4mm .05ct
2.5mm .06ct
2.6mm .07ct
2.7mm .08ct
2.8-2.9mm .09ct
2.9-3.0mm .10ct
3.5mm .15 to .20ct
4mm .25ct
4.5mm .33ct
5mm .50ct
5.5mm .66ct
6mm .75ct
6.5mm 1.0ct
7.0mm 1.25ct
7.4mm 1.5ct
7.8mm 1.75ct
8.2mm 2ct
Oval Stones
3x5 .25ct
4x6 .50ct
5x7 .75ct
6x8 1.5ct
7x9 2.0ct
Marquise Stones
2x4 .10ct
2.5x5 .20ct
3x6 .35ct
4x8 .75ct
5x10 1.0ct
MM Width to Carat Weight, conta.
Pear Stones
3x5 .25ct
4x6 .50ct
5x7 .60ct
6x8 .90ct
6x9 1.25ct
7x9 1.5ct
8x10 1.75ct
Baguette Stones
2x4 .15ct
5x3 .30ct
3x6 .50ct
Emerald Cut Stones
3x5 .25ct
4x6 .50ct
5x7 1.0ct
5x8 1.75ct
7x9 3.0ct
8x10 4.0ct
Square Cut Stones
3x4 .20ct
4x4 .50ct
5x5 .60ct
6x6 1.0ct
Trillion cut Stones
4x4 .50ct
5x5 .75ct
6x6 1.0ct
7x7 1.5ct
8x8 2.0ct
Birthstones
January Garnet
February Amethyst
March Aquamarine
April Diamond
May Emerald
June Pearl / Alexandrite
July Ruby
August Peridot
September Sapphire
October Opal / Tourmaline
November Topaz
December Blue Zircon
Abbreviations
Carat ct.
Pound lb.
Millimeter mm.
Gram gr.
Grain gn.
Pennyweight dwt.
Avoirdupois avoir.
Ounces oz.
Water / Investment Ratios
Flask Dia. Ht. Water Investment
2x2 57cc 5 oz.
2x2.5 68cc 6 oz.
2.5x2 91cc 8 oz.
2.5x2.5 114cc 10 oz.
2.5x3 136cc 12 oz.
3x2 136cc 12 oz.
3x2.5 170cc 15 oz.
3x3 205cc 18 oz.
3x3.5 240cc 21 oz.
3x4 274cc 24 oz.
3.5x3 274cc 24 oz.
3.5x3.5 320cc 28 oz.
3.5x4 364cc 32 oz.
3.5x5 456cc 40 oz.
4x3 308cc 27 oz.
4x3.5 354cc 32 oz.
4x4 410cc 36 oz.
Ring Blank Lengths in MM
Ring Size 16 ga. 18 ga. 20 ga.
3 48 47.1 46.5
3 + 49.3 48.4 47.7
4 50.6 49.6 49.0
4 + 51.8 50.9 50.2
5 53.7 52.8 52.1
5 + 54.3 53.4 52.7
6 55.6 54.6 54.0
6 + 56.8 55.9 55.3
7 58.1 57.1 56.5
7 + 59.3 58.4 57.8
8 60.6 59.7 59
8 + 61.9 60.9 60.3
9 63.1 62.2 61.5
9 + 64.4 63.4 62.8
10 65.6 64.7 64.1
10 + 66.9 65.9 65.3
11 68.1 67.2 66.6
11 + 69.4 68.5 67.8
12 70.7 69.7 69.1
12 + 71.9 71.0 70.3
13 73.2 72.2 71.6
Metal Melting Points (Fahrenheit)
Brass 930
Copper 2000
Silver (fine) 1760
Sterling 1640
10k Gold 1665
14k Gold 1615
18k Gold 1700
24k Gold 1945
Platinum 3223
Most of these formulas were taken from industry journals such as
Hoover & Strong, Stuller Settings, and Oppi UntrachtAEs “Jewelry
Concepts and Technology”.