melting in cupel

[Anonymous]

Since I do small lots and I keep breaking melting dishes. I want to melt in a
magnesite cupel hopefully this works since I just ordered some, if it is ok how much silver or gold will I be able to melt. I usually only do about 5gr batches.
Will they hold to melt palladium or platinum?

thanks
jim

 

[lazersteve]

Jim,

They hold an ounce or better melted.

They are pretty robust, but I'm not sure you can melt Pt or Pd in them.

The trick to not breaking a dish is to heat it slowly and evenly before you ever add any metal. The dish should make a creaking noise before you apply any amount of serious heat to the dish.

Once the dish is seasoned and glazed with borax, then you can put the heat to them.

Steve

 

[Anonymous]

Hi Steve,
I had 2 dishes that worked for a long time, but now, seems I can not get through the seasoning stage, so I surrendered.

Jim

 

[Barren Realms 007]

Jim,

They hold an ounce or better melted.

They are pretty robust, but I'm not sure you can melt Pt or Pd in them.

The trick to not breaking a dish is to heat it slowly and evenly before you ever add any metal. The dish should make a creaking noise before you apply any amount of serious heat to the dish.

Once the dish is seasoned and glazed with borax, then you can put the heat to them.

Steve

I heated mine slowly in my oven and still cracked it.

 

[Anonymous]

Hey Guys,
Steves cupels arrived today, thank you Steve.

Now some questions that I should have asked first :idea:
Can I melt in them more than one time, just like a dish?
Will borax, soda ash, or potassium nitrate in molten form harm them much?
Do they need to be seasoned (read babied) like melting dishes.

The reason I ask and not just try and see what happens is that I have some melts to melt into a beads for a couple people that have been very patiently waiting on me to have some free time to get thier jobs done. I do not want to risk ruining the cupels and having to wait for more to arrive.

thanks
jim

 

[lazersteve]

Hey Guys,
Steves cupels arrived today, thank you Steve.

Now some questions that I should have asked first :idea:
Can I melt in them more than one time, just like a dish?
Will borax, soda ash, or potassium nitrate in molten form harm them much?
Do they need to be seasoned (read babied) like melting dishes.

The reason I ask and not just try and see what happens is that I have some melts to melt into a beads for a couple people that have been very patiently waiting on me to have some free time to get thier jobs done. I do not want to risk ruining the cupels and having to wait for more to arrive.

thanks
jim

Jim,

Normal use for cupels is for assaying and no preparations are required on the cupel.

For melting treat the cupel like a dish with borax ( ie: a thin glaze only).

The magnesite cupels are very durable and should give you several melts of clean metals before failing. Base metals will contaminate the cupel quickly as the are designed to absorb base metals in assays.

No need to 'baby' then like the dish, but a gentle preheat is still recommended to prevent any trapped water from causing a steam explosion and chipping the cupel. This preheating can be accomplished at the same time the cupel is glazed with borax.

The cupels are susceptible to being dropped and excessive moisture.

Steve