GOLD ANNEALING CRUCIBLES & PARTING FLASKS

GOLD ANNEALING CRUCIBLES, PARTING FLASKS AND OTHER ACCESSORIES

PARTING PROCESS IN CUPELLATION

After cupellation, we obtain a bead made of gold and silver. Therefore, it is still necessary to separate the silver from the gold . In order to achieve this, we attack two times the bead with boiling nitric acid and then we anneal it. This process is called “parting” and “annealing”Gold annealing crucibles and parting flasks are the key instruments to achieve this.

The reason for using nitric acid, is that silver is soluble in it but gold is not.  However, to ensure that no silver is secluded into the gold, and therefore protected from being dissolved, it is first necessary to laminate the bead into a cornet.

Finally, it is possible to do the nitric acid attack in quartz parting and annealing crucibles or in borosilicate parting flasks. Particularly, Quartz parting and annealing crucibles have the advantage of requiring less manipulation of the bead because the next step of the process  (gold annealing) is done using this same crucible. 

GOLD ANNEALLING PROCESS IN CUPELLATION

After the nitric acid attack, the obtained pure gold cornet is very brittle because it is covered by a multitude of holes left by the dissolved silver. At this point, it would be unsafe to weight the gold cornet due to the risk of breaking it and losing a part of the sample. For this reason , it is necessary to anneal the gold cornet in a quartz parting and annealing crucibles , fireclay crucible or porcelain crucible. 

 

Therefore, the Annealing process consists of just heating the gold cornet above its recystalization tempearute (850ºC) but without melting it. After annealing, the cornet can be safely weighted withou risk of breaking it.

 

Fire Assay SL supplies the parting and annealing accessories to achieve this:

Fire Assay / Cupellation Borosilicate parting flasks
Fire Assay / Cupellation Borosilicate parting flask
Range of Gold annealing crucibles
Range of Gold annealing crucibles
Gold Annealing unglazed porcelain crucible
Gold Annealing unglazed porcelain crucible
PORCELAIN CRUCIBLE FOR PARTING AND ANNEALING ACCORDING TO ISO 10378
Gold annealing and parting porcelain crucibles according to ISO 10378
Quartz Parting & annealing basket for 25 samples
Quartz Parting & annealing basket for 25 samples
BOROSILICATE GLASS PARTING FLASKS
Fire Assay / Cupellation Borosilicate parting flasks
Parting Flask

Parting Flask made with low thermal expansion borosilicate glass withstands both nitric acid attack and thermal shock.

Additionally, they have a tall narrow neck designed to fit inside gold annealing cups.

Finally, the dimensions of our parting flasks are: 230 x Ø 48 x Ø 18

FIRECLAY CUPS – GOLD ANNEALING CRUCIBLES ACCORDING TO ISO 11426
Range of Gold annealing crucibles
Range of Gold annealing crucibles
Gold annealling crucibles and cupel tray P51
Gold annealling crucibles and cupel tray P51

Fireclay or Unglazed Porcelain Annealing Cups / annealing crucibles possess a smooth unglazed surface and thin walls that provide them with excellent resistance against thermal shock. 

Furthermore, they have a tronco-conical form designed for gold bead annealing and for ignition of precipitates such a barium sulphate and copper sulphide.

ReferenceHeightDIameterPicture
PORCELAIN UNGLAZED CORNET ANNEALING CUPS nº 2263335Porcelain Unglazed Gold Annealing Crucibles
CORNET ANNEALING CUPS nº 2272525Gold annealing crucibles 25 x 25
CORNET ANNEALING CUPS nº 2303230Gold Annealing Crucibles 30 x 32
CORNET ANNEALING CUPS nº 2313334Gold annealing crucibles 34 x 33
Gold Annealing Crucibles

PORCELAIN CRUCIBLE FOR PARTING AND ANNEALING ACCORDING TO ISO 10378

Glazed porcelain crucibles to perform the parting and annealing process according to ISO 10378.

 

ReferenceHeigt / mmTop Diameter / mmVolume / mL
MW-521255
MW-10283010
MW-15303515
MW-25364025
MW-30414230
MW-40424840
MW-50465350

PORCELAIN CRUCIBLE FOR PARTING AND ANNEALING ACCORDING TO ISO 10378
Gold annealing and parting porcelain crucibles according to ISO 10378