| Purpose |
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S-88 is a master alloy for adding to fine
silver to make Sterling Silver.
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This alloy was developed for those who wish
to alloy their own sterling.
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S-88 will cast without fire scale.
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The advantages over standard sterling are:
reduced gas porosity (S-88 contains deoxidizers which resist oxygen absorption),
reduced shrinkage porosity (better solidification characteristics reduce
shrinkage), S-88 alloy may be reused indefinitely with a 50% fresh mix,
and less finishing rejects from fire scale and porosity.
|
| Melting |
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Traditional methods of melting regular sterling
silver (ie. as cool as possible) will cause a variety of problems.
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Most failures S-88 alloy are caused by too
low of a melt temperature.
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Metalsmiths familiar with silicon deoxidized
gold casting alloys should have less trouble adjusting to the appearance
of the silver.
|
| Mixing |
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Use 92.5% fine silver & 7.5% S-88.
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92.7% fine silver & 7.3% S-88 is recommended.
Example: 500 dwt, add 462.5 dwt of fine silver & 37.5 dwt S-88.
|
Melting and Casting
Temperatures |
-
Melting temperature for mixing sterling: 1040°
C, 1904° F.
-
Temperature range for casting sterling: 990°
- 1020°C, 1814° - 1868° F.
|
| Fluxing |
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Boric Acid is the recommended flux.
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Do not use Carbon Containing Fluxes or
Charcoal.
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Skim any surface oxides off the surface before
stirring.
|
| Quench Time |
|
Hardness and
Heat Treatment |
-
This silver as cast will have a hardness similar
to traditional sterling silver. It can be hardened further by heat treatment
at 300° C / 575° F for one hour.
|
| Investment Removal |
-
Most standard investment removers will successfully
remove the investment powder. The best solutions are the sulfuric and hydrofluoric
based products.
|
| Re-Melting |
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50% fresh mix is recommended.
|
| Flask Temperature |
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Use your regular flask temperatures.
|
| Notes |
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Fire scale is completely eliminated.
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CYANIDE TREATMENT is Not recommended.
|
