First fire assay questions

[goldshark]

I have a cone mold. I pour within 15 seconds, probably in less than 10 actually. This second batch was super thick even when white hot as I mentioned.

Is there any way around an expensive balance? I simply cannot afford one like that. It's also not incredibly important to get super accurate results. I was thinking If I measured the bead, calculated the volume of a sphere and with the density of gold it would give me the weight. Of course that only works for pure gold. But if a simple color test could tell me the bead was at least 50% gold, I should be able to get a rough idea of what.

Example, volume of 0.002" bead X density of gold gave me 1.32mg. If 100% silver, 0.72mg. So at least 50% gold should give me somewhere in the middle around 1 oz/tn.

If I can verify I have at least 0.5oz/tn it's a go for running all the material anyway.


Thanks for the tip on the furnace. I wish I could find an electric one that was affordable.

One of the simple scratch test kits, available for testing Karat purity used by jewelers and pawn shops, will get you in the ball park for Karat/percentage.

 

[4metals]

One of the simple scratch test kits, available for testing Karat purity used by jewelers and pawn shops, will get you in the ball park for Karat/percentage.

This may be a challenge with a 1.3 mg bead!

 

[4metals]

A question about the gas fired furnace you are using for the assay furnace. How high above the cupel does the flame enter the furnace? I know that even when melting, if the flame is not below or at a minimum equal to the height of the bottom of the crucible, the crucible contents do not melt quickly as the bottom does not reach temperature quickly. This is why a crucible rest is used to get the bottom of the crucible above the flame entering and swirling around in the furnace.

If your crucible is sitting on the bottom of the furnace and the flame is above it, that can explain the exceptionally long time the cupellation takes to go to completion.

 

[IDAu]

A question about the gas fired furnace you are using for the assay furnace. How high above the cupel does the flame enter the furnace? I know that even when melting, if the flame is not below or at a minimum equal to the height of the bottom of the crucible, the crucible contents do not melt quickly as the bottom does not reach temperature quickly. This is why a crucible rest is used to get the bottom of the crucible above the flame entering and swirling around in the furnace.

If your crucible is sitting on the bottom of the furnace and the flame is above it, that can explain the exceptionally long time the cupellation takes to go to completion.

I don’t think too of Low of heat is the problem. The flame enters at the bottom. If anything I think I can’t adjust it low enough. It starts to sputter when I try to get the cupel at a dull red.


Anyone know about iron heavy pills? An assayer said if there is a lot of iron it will take forever to melt and I need to do something called scarification.

I did read a chart that said iron causes “slow melting”

 

[Yggdrasil]

I don’t think too of Low of heat is the problem. The flame enters at the bottom. If anything I think I can’t adjust it low enough. It starts to sputter when I try to get the cupel at a dull red.


Anyone know about iron heavy pills? An assayer said if there is a lot of iron it will take forever to melt and I need to do something called scarification.

I did read a chart that said iron causes “slow melting”

You need to read and study some reputable books on fire assaying.
Scorification done as a fusion process before cupelling.
Much Iron will make the cupelling "impossible".

And what 4metals said was that you need to make sure there are room under you crucible and that itvis high enough to be subjected to the hottest part of the flame.
At least for the smelting.
Next your cupel should be lifted high enough so you can adjust both heat and oxygen access.
The cupel should have some 860-900 C. And make sure the cupel is red hot (correct temperature) before you put in the Lead "packet".

 

[4metals]

If you go to the video section you will see an entire section of videos by Rob Boyko on fire assay. That includes this video on scorification.

 

[IDAu]

You need to read and study some reputable books on fire assaying.
Scorification done as a fusion process before cupelling.
Much Iron will make the cupelling "impossible".

And what 4metals said was that you need to make sure there are room under you crucible and that itvis high enough to be subjected to the hottest part of the flame.
At least for the smelting.
Next your cupel should be lifted high enough so you can adjust both heat and oxygen access.
The cupel should have some 860-900 C. And make sure the cupel is red hot (correct temperature) before you put in the Lead "packet".

That’s why I asked. I think he may have mixed up terms. Everything I read made it sound like a different process, not something you do after fusion.

He described it as getting it liquid in a melting dish, letting a litharge crust form, and pouring it off into another mold to cool, adding more lead and repeating until it’s the size you want. Apparently, this will get rid of the iron contamination.

I only found one person on YouTube doing something similar. Everything else I read on scorification sounds different

 

[4metals]

I respectfully suggest you sit down with a hot refreshment of choice and spend some time watching some of Rob's video's, they are in the video library. They will answer all of your questions. If you watch the video's and take notes and compare what you are doing to what he suggests you can eliminate any errors you may be making. Armed with this knowledge you can come back here and discuss your findings. The video's can answer questions instead of days of posting and responding here. His video's do cover all types of ores and fluxes so the answer is there.

 

[IDAu]

I respectfully suggest you sit down with a hot refreshment of choice and spend some time watching some of Rob's video's, they are in the video library. They will answer all of your questions. If you watch the video's and take notes and compare what you are doing to what he suggests you can eliminate any errors you may be making. Armed with this knowledge you can come back here and discuss your findings. The video's can answer questions instead of days of posting and responding here. His video's do cover all types of ores and fluxes so the answer is there.

Watched a couple of them. Wish I would’ve found his channel months ago.


I have an interest in deep diving into this because it’s fun. Right now I’m just trying to get it down and dirty prospecting fire assay procedure that works. Other than the four hour cupel time the first one went beautifully