here's another thing to consider:
The xrf Mystery
- Thread starter benign01
- Start date
Help Support Gold Refining Forum:
NobleMetalWorks
Well-known member
First, if you do not correctly melt (stirring, mixing, observing, correcting), and pour your bars incorrectly, the heavier gold will try to move towards the bottom. A melt has to be one homogenous mass, meaning no dark spots and having a nice uniform color before you pour into a mold. But if you take a mass that has not been melted correctly, and pour it into a mold, in the center lets say, the gold that isn't melted correctly with the rest of the metal will try to travel to the bottom and dependent upon how fast the bar becomes solid, it might or might not make it. So all along the outside of the bar might read lower than the inside. The top might read differently than the bottom. When the top and bottom are drilled and the shavings hit with an XRF gun, you might be getting a of 5 shaving amounts from low content areas, and one shaving reading from the sweet spot in the middle of the bar. And how can you accuse them of ripping you off if they are just testing your bar?
I don't understand the concern over being able to flip a switch on an XRF to read differently. It wouldn't even take that much. When I owned a grocery store I had to constantly watch for people ripping me off using all kinds of different methods. Unfortunately, because I would like to believe everyone is good, my experience has been that if you give someone an opportunity to steal from you, eventually they will. A common way to rip off the store you work for as a cashier is to do what is called sweethearting, selling things for less than their worth, to friends and family. I have seen a lot of sweethearting and some pretty clever ways to do it. I had a 19 year old girl who tapped a barcode under her bracelet and would simply cover the barcode with her hand, and then move her bracelet to scan the barcode on her wrist. Forget about the calibration, if someone wants to rip you off it just takes a small piece of metal, nothing more. By scanning one time, and then a second time, they can get the reading of the actual content, and then force a second reading with another small sample you don't see, and get the reading they want not too far off from your own. This is just a suggestion of how it could be done.
Also, don't forget XRF scanners operate on software, anything that has software can be altered, no switch required.
Third party fire assay is the way to go.
Scott
I don't understand the concern over being able to flip a switch on an XRF to read differently. It wouldn't even take that much. When I owned a grocery store I had to constantly watch for people ripping me off using all kinds of different methods. Unfortunately, because I would like to believe everyone is good, my experience has been that if you give someone an opportunity to steal from you, eventually they will. A common way to rip off the store you work for as a cashier is to do what is called sweethearting, selling things for less than their worth, to friends and family. I have seen a lot of sweethearting and some pretty clever ways to do it. I had a 19 year old girl who tapped a barcode under her bracelet and would simply cover the barcode with her hand, and then move her bracelet to scan the barcode on her wrist. Forget about the calibration, if someone wants to rip you off it just takes a small piece of metal, nothing more. By scanning one time, and then a second time, they can get the reading of the actual content, and then force a second reading with another small sample you don't see, and get the reading they want not too far off from your own. This is just a suggestion of how it could be done.
Also, don't forget XRF scanners operate on software, anything that has software can be altered, no switch required.
Third party fire assay is the way to go.
Scott
Dan Dement
Well-known member
- Joined
- Feb 22, 2012
- Messages
- 243
benign01 said:
The answer is yes. Also, you can set up the XRF to read correctly on .999 and be off on 14kt. It's a matter of having to adjust the standards. Sometimes on 14kt Gold, you can have 3 to 9 or more different alloys. I have my fourth XRF machine on order.
Dan Dement
Lobby
Well-known member
One of the refiners in town buys gold filled jewelry.
Since GF jewelry is normally around 2% gold, and it can vary all over the place, the refiner MUST have standards in those concentration ranges to pay accurately. Or, to make sure he doesn't overpay. :mrgreen:
The GF jewelry I've melted has copper as the major component, but there's lead and tin there also, in addition to the gold.
Since GF jewelry is normally around 2% gold, and it can vary all over the place, the refiner MUST have standards in those concentration ranges to pay accurately. Or, to make sure he doesn't overpay. :mrgreen:
The GF jewelry I've melted has copper as the major component, but there's lead and tin there also, in addition to the gold.
benign01,
We own a Niton XRF machine as well and the same thing happened to us. Our refiner used to drill on both sides of the bar and we would get bad readings, usually 2% lower. However they did melt all bars prior to the XRF analysis and then would make one larger bar, then the drilling would happen. So we decided to change refineries and explained our situation with the old one and they said something like drilling is an old method and is not as precise. We have been using this new refinery for some time now and they first melt everything together to make one larger bar, they mix everything up and use a Pin sample. (Which we also use back home). With that pin sample an initial essay is done with an XRF machine and accept part of the payment until the complete essay is done with a fire essay. So we can compare our results from theirs and when the fire essay is done there usually is a higher difference of 0.2-0.35% difference of the initial analysis and we get payed the extra amount.
So I believe it might have to do with the shavings. I also remember that when we bought the XRF our rep in the factory told us that air between the gold and the gun could make a difference. I don't know how accurate that is, but every time we test gold we put it as flat as we can.
Hope that helps.
We own a Niton XRF machine as well and the same thing happened to us. Our refiner used to drill on both sides of the bar and we would get bad readings, usually 2% lower. However they did melt all bars prior to the XRF analysis and then would make one larger bar, then the drilling would happen. So we decided to change refineries and explained our situation with the old one and they said something like drilling is an old method and is not as precise. We have been using this new refinery for some time now and they first melt everything together to make one larger bar, they mix everything up and use a Pin sample. (Which we also use back home). With that pin sample an initial essay is done with an XRF machine and accept part of the payment until the complete essay is done with a fire essay. So we can compare our results from theirs and when the fire essay is done there usually is a higher difference of 0.2-0.35% difference of the initial analysis and we get payed the extra amount.
So I believe it might have to do with the shavings. I also remember that when we bought the XRF our rep in the factory told us that air between the gold and the gun could make a difference. I don't know how accurate that is, but every time we test gold we put it as flat as we can.
Hope that helps.
I am still learning, but so far, my XRF numbers are always accurate to the second decimal point of what i get settled out with from the Royal Canadian Mint.
We only use pin samples, you can mess with bar readings pretty easily.
We only use pin samples, you can mess with bar readings pretty easily.
Dan Dement
Well-known member
- Joined
- Feb 22, 2012
- Messages
- 243
Fasttcar & All,
I have jewelers who do not like to use my induction melters but prefer to use a torch. When you torch melt metal, I seen as much as 20% difference from one side to another. When you melt metals in an Induction Melter, usually you have have a 2-3% difference in reading all the sides. Pulling a pin sample from a running IM is fairly accurate. However, as soon as por the metal into a mold, the stratification and solidification starts. Every notice how the top of the bar starts out smooth and then forms a "bread loaf" effect with the top having a dip in it. Zinc & copper really moves around in the cooling process which makes getting a true average difficult. I pour my bars in a wedge my tilting the ingot mold at an almost 45 Degree angle. This method helps push the lower and higher reading to a constant. By running 7 readings on all the sides and comparing it to SG readings, you can get a very good average which is a constaint fair payout. With well over 100 payouts using this method, I am well within a $500 window on over a million dollars.
All I say is that it works for me.
Dan
I have jewelers who do not like to use my induction melters but prefer to use a torch. When you torch melt metal, I seen as much as 20% difference from one side to another. When you melt metals in an Induction Melter, usually you have have a 2-3% difference in reading all the sides. Pulling a pin sample from a running IM is fairly accurate. However, as soon as por the metal into a mold, the stratification and solidification starts. Every notice how the top of the bar starts out smooth and then forms a "bread loaf" effect with the top having a dip in it. Zinc & copper really moves around in the cooling process which makes getting a true average difficult. I pour my bars in a wedge my tilting the ingot mold at an almost 45 Degree angle. This method helps push the lower and higher reading to a constant. By running 7 readings on all the sides and comparing it to SG readings, you can get a very good average which is a constaint fair payout. With well over 100 payouts using this method, I am well within a $500 window on over a million dollars.
All I say is that it works for me.
Dan
solar_plasma
Well-known member
Now I am deaf, thanks for that. :lol: Did you serve at the artillery, so you have to shout all the time?
badran106,
Typing in all capitol letters is considered yelling and bad manners on the forum, typing text lingo is forbidden, and members are asked to use spell check to insure other readers can understand or do not get hurt if they cannot translate the message properly.
There are rules here on the forum which are easy to follow, these rules are to insure we all here have a great forum where we can all learn from each other without trouble, and to help keep our forum the best place to learn about recovery and refining of the precious metals.
Take a little time and read these rules, so that you also will get along well with the forum and its members.
And please do not shout unless you are trying to help someone by telling them to:
READ C.M. HOKE'S BOOK
(because they do not seem to hear this important message when we say it softly).
Look in the book section for Hoke's book (She has two books one on testing precious metals and one on recovery and refining).
Another very helpful tool is the guide to the forum found in the general chat section, taking the tour through the links can help you get a better understanding of much of what is discussed.
The safety section also a must read, and dealing with waste a topic in that section is also a must read for anyone processing, understanding how to deal with the waste and process safely is more important than recovering gold (as gold is not much good to dead men).
Welcome to the forum, spend some time studying the valuable information provided on the forum, to learn the skill, science, and art of recovery and refining of precious metals is a major study, and is a lifetime of work, but worth every bit of the work needed.
Typing in all capitol letters is considered yelling and bad manners on the forum, typing text lingo is forbidden, and members are asked to use spell check to insure other readers can understand or do not get hurt if they cannot translate the message properly.
There are rules here on the forum which are easy to follow, these rules are to insure we all here have a great forum where we can all learn from each other without trouble, and to help keep our forum the best place to learn about recovery and refining of the precious metals.
Take a little time and read these rules, so that you also will get along well with the forum and its members.
And please do not shout unless you are trying to help someone by telling them to:
READ C.M. HOKE'S BOOK
(because they do not seem to hear this important message when we say it softly).
Look in the book section for Hoke's book (She has two books one on testing precious metals and one on recovery and refining).
Another very helpful tool is the guide to the forum found in the general chat section, taking the tour through the links can help you get a better understanding of much of what is discussed.
The safety section also a must read, and dealing with waste a topic in that section is also a must read for anyone processing, understanding how to deal with the waste and process safely is more important than recovering gold (as gold is not much good to dead men).
Welcome to the forum, spend some time studying the valuable information provided on the forum, to learn the skill, science, and art of recovery and refining of precious metals is a major study, and is a lifetime of work, but worth every bit of the work needed.
