# The xrf Mystery



## benign01 (Dec 6, 2011)

So I've been getting some low test results on my bars. Refiner fiddling? or somehow I' m missing something.

I melt scrap gold into bars and then watch the refiner as he drills a sample from both sides of the bar and then tests the sample using a handheld Niton XRF analyser.

My question is a simple one. Can you fiddle the xrf test results, if so how exactly? Can you really calibrate 14k gold to read 56% instead of 58.5% as I I read somewhere on these forums? 

How is this done? How is the xrf analyser actually calibrated for precious metals? Can I really turn down or lower the reading by falsely calibrating the gun?

I could go out and buy myself a gun but that's one expensive way of finding out! Does anyone on here actually know the answers to these questions?.

For many reasons I do not want to change the refiner I use if I can avoid it and whilst I fully appreciate fire assays are more accurate they are for a number of reasons best known to myself impractical for me. So I'd rather not go off topic here, Sorry if I sound condescending but I'd really like to know the answer specifically to my question

Many Thanks and go easy on a newbie

Ben


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## qst42know (Dec 6, 2011)

This has been discussed quite a bit on the forum and yes they can be adjusted to read as the operator wishes.

The simple solution is to bring a bullion coin (four nines Canadian maple leaf or a 90% US coin) with you and have them test it.


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## benign01 (Dec 7, 2011)

That's quite a statement. Not the bit about it being discussed on this forum, I knew that anyway, more to do with the statement "they can be adjusted to read as the operator wishes...." Explain exactly how that can be done. Can it be set to read 14ct as 9ct for example?

Also how will taking a pure gold coin help you? Don't they just flick a switch to select a different calibrated setting (ie more accurate) and using another calibrated setting on the gun give you the right sort of reading? 

These guns can be set to read as the operator wishes!! To what degree???


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## qst42know (Dec 7, 2011)

As I understand it they must be calibrated to a known standard. The mechanics of calibration are unknown to me as I have never operated one. Hopefully this is an internal adjustment and not just another button. 

Perhaps someone who has calibrated these machines will respond to the complexity of the adjustments.

As far as scanning a genuine bullion coin it should be obvious that if the readings are off from what you know your test coin should read your buyer either failed to calibrate the device properly or adjusted it to give themselves a wider margin. A bullion coin you provide, should reveal the accuracy of the scan of your bar and whether you are being paid accurately or not.

It's certainly not unheard of for marked 14k to be under karat or to be fooled by very good fakes. 

Are you certain you thoroughly removed any fire scale and stirred your melt?


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## benign01 (Dec 7, 2011)

Always stir the melt and no fire scale . 
I'd like to hear from someone who has calibrated one of these machines I guess. Saying re the calibration that "


> Hopefully this is an internal adjustment and not just another button.


 highlights one question but doesn't answer it .

Using a pure coin to check calibration is all well and good for pure, but what is the 14k calibration is out OR what if once the coin is checked a button is pressed and a second lower calibrated scale is then used
There must be someone out there that knows the answers to these questions. perhaps we should ask Niton or some other company directly


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## qst42know (Dec 7, 2011)

I see from your profile you are located in the UK. It has been mentioned many times that proper assays are readily available in the UK and inexpensive. Pay the fee and sell based on the result is the simplest answer.


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## nickvc (Dec 8, 2011)

I also am UK based and wouldn't trust an xrf to be paid on because as you have found many read below what is actually there. They can be set very accurately if needed and I believe they have to be programmed using known standards across a variety of carat golds to be accurate , most don't seem to bother and even the better desk top models seem to be inaccurate on low gold bearing materials. As advised why not just drill top and bottom of the bar and get an assay it's quick and cheap here £10 for gold and same day answer from the lads I use.


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## benign01 (Dec 8, 2011)

Main reason I don't get an assay is because very few refiners use THE Assay Office results!! They prefer to use a private assay company's results, so what is the point of doing that? The official Assay Office result is ignored and either you accept the private company's result OR you have to go elsewhere. An assay from anyone other than the Assay Office is just not reliable..or is it? 
Who do you use?


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## nickvc (Dec 8, 2011)

Most refiners will accept Sheffield Assay Office results happily the other offices aren't so rated.
I use Guardian Laboratories here in Birmingham 0121 359 8233 if you get a sample to them by lunch time the assay is ready by about 4pm if your not local post the sample and have the packet returned by post, if you actually need the certificate it's usually delivered next day or you can ask them to deliver to your refiner if they are in Birmingham. I usually give them my estimate of the % and give them around 1/2 gram of sample, if your testing for other values they need a larger sample and the costs obviously go up, full Au Pt Pd Ag assays are about £60 if I remember correctly and take around 2-3 days and a sample of at least 1-2 grams is needed.


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## benign01 (Dec 8, 2011)

I refer to my original question and add another
Does an xrf analyser test differently if the gold content is relatively low eg 2%... What I mean is does the accuracy vary with lower amounts?

Any takers?


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## bryantch (Dec 8, 2011)

It is possible to adjust any XRF to read high or low. BUT, a pro unit like the Niton is not easily reconfigured like some of the precious metal specific xrf manufacturers out there (Chinese imports sold by gold dealers in NY).

I own a Niton xl3t handheld and that was a question I asked before I purchase it because the refiner I use told me a salesman had pitched them on another system touting the ability flip a switch to under carat the gold when purchasing.
I was told how to do it on the Niton but it is not simple and it is time consuming.
If you scan a known 24 k piece and it is nuts on, it is unlikely they are cheating. If you had a lab sample 14k reference you could also use that to make sure they weren't cheating. Lab samples are available for about $400.

Now refineries underpaying even with multiple xrf scans prior to shipment...don't get me started.


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## benign01 (Dec 8, 2011)

Thanks & Useful to know, bryantch, especially with regard to the Niton ie "I was told how to do it on the Niton but it is not simple and it is time consuming." I presume that means "time consuming" every time they want to fiddle?

We all know paranoia is rife in this game. I've made several attempts to check my buyers xrf results ie by giving him pre-assayed samples etc and was reasonably confident his gun was accurate but wasn't sure about the "flip a switch and get a lower reading thing!!" I mean lets face it the easiest way to tell if they are on the fiddle is to look at their setup. if they are paying 98-99% and they have large expensive buildings and a load of staff....they're fiddling!!!, the margins just don't add up!

What about the Niton's accuracy re low gold levels say 2-3%??


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## nickvc (Dec 9, 2011)

From what I've seen and been told low grade materials really don't test accurately on the xrf guns even the more expensive fixed units aren't that good on very low grade materials. I'm sure if they are calibrated to run low grade then they will be much more accurate but most are set for carat gold purchasing which is what most refiners are buying in and in large bulk.
The assumption that refiners can't make an honest profit paying 98-99% of fix is understandable but if they move seriously large amounts of gold then yes they can as they get bonus metals like silver and PGMs for free and if they move say 30 kilos of fine gold a day and can make 1.5% that's 450 grams of gold worth close on £16000 plus any bonus metals, not to bad in my opinion for a days work, and don't forget the silver scrap which as we all know frequently has gold mixed in by accident and is again a freebie for the refiner, I have known shipments of 100 kilos yield 200-300 grams of gold.


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## benign01 (Dec 9, 2011)

.and how many in the UK are moving 30 kilos of fine gold a day ?? ie £1£million a day.and how many are actually *refining it*.....None of the guys I know No one sells it for 100% to the real refiners ie non-UK .and what about errors,silver or brass in the gold, gold price drops? and how many staff would you really have to have to handle 30 kilos a day of pure ie 80 kilos of 9ct a day?

I don't get it

And I also dont understand how you can get an accurate test from a drilling of a bar ie as opposed to cupellation of the whole bar?


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## 4metals (Dec 9, 2011)

You are making the mistake that many gold buyers make and that is an XRF is a great tool for buying scrap but it is not the right method for settling a refining lot. Lots of collectors are willing to settle on an XRF because it is fast but it is not anywhere as good as a fire assay. 

Take some time and read through this thread http://goldrefiningforum.com/phpBB3/viewtopic.php?f=72&t=3166

It will help you get closer to the real number if you're willing to follow all of the steps in witnessing and assaying.


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## benign01 (Dec 9, 2011)

Very very useful, many thanks


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## eeTHr (Dec 9, 2011)

So, if a good assay from an acceptable company is best, how does the buyer know that the assay report is actually for the bar the seller presents to him?

Couldn't the assay report be for a different bar altogether?

:?:


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## 4metals (Dec 9, 2011)

In the old days the buyer (refiner) and the seller (scrap owner) actually interacted, the seller actually went to a refinery to melt the lot and physically took a sample. Today we live in a fast paced world, scype, tweet, and I guess we can add XRF! Sure its faster but there is a cost. Personal contact business relationships are tough to beat.


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## eeTHr (Dec 9, 2011)

4metals---

It sounds like you are saying that the seller's assay is so the seller knows if the buyer is being accurate. Which means the buyer is doing an assay, anyway.

What I meant is, that someone said that a certain buyer refinery will accept (pay on) a certain reputable assayer's report.

How does the buyer know that the assay report is actually from the bar which he is paying for?


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## 4metals (Dec 9, 2011)

If a refiner and a seller develop a relationship I guess that's possible but from the perspective of a refiner I can't see paying without assay verification which always involves re-melt and re-assay. Today refiners will advance 90% on XRF and settle on fire assay.


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## bryantch (Dec 9, 2011)

As with all tools at the disposal of a gold buyer, an XRF is just one more. Although some may argue, an xrf is very accurate in the hands of an experienced operator...key word,"experienced". Results within 1/2% of a fire assay are expected.

With regards to detection of low gold concentrations, I know of no reason to expect a lesser degree of accuracy. Xrf machines are routinely used to detect low levels of heavy metals in contaminated soils and are also commonly used in mining operations to test gold and silver ores.


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## nickvc (Dec 10, 2011)

.and how many in the UK are moving 30 kilos of fine gold a day ?? ie £1£million a day.and how many are actually *refining it*.....None of the guys I know No one sells it for 100% to the real refiners ie non-UK .and what about errors,silver or brass in the gold, gold price drops? and how many staff would you really have to have to handle 30 kilos a day of pure ie 80 kilos of 9ct a day?

And I also dont understand how you can get an accurate test from a drilling of a bar ie as opposed to cupellation of the whole bar?[/quote]

Their are several that I personally know of that move that sort of volume or close to it and in volume you can get very very good terms and one of the largest refiners in the world is UK based Johnson Matthey and several have depots to accumulate metals including Englehard and Metalor. The errors due to xrf testing are few and most will pay by carat so if its over 21 k they pay 21 or 20 k and most buyers of volume cover the metals they buy as they buy so no risk there. Very few staff are needed as the bigger buyers have large collectors and one has deals worldwide and not just jewellery scrap is traded remember but every type of precious metal scrap available and tradable.

With taking samples it really comes down to melting and mixing properly and most professional melters take dip samples but if you just do odd bars a drilling sample taken top and bottom at opposite ends of the bar will normally give you a fair result and if you know what you melted your rarely shocked, in other words if you really grade your scrap as you buy you should know exactly what assay to expect.


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## benign01 (Dec 10, 2011)

OK, yes you are right here, but how many 98% payers in Birmingham are doing JM volumes?


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## nickvc (Dec 10, 2011)

As I said I know of two personally who probably move 30 kilos a day and maybe more and in those quantities and with the deals they will have with the big refiners 1 -1.5% is not not out of the question as a margin and plus the bonus metals, so yes they make good money believe me they don't need to cheat and it's up to you to give them no reason to by getting assays simple quick and cheap here.


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## benign01 (Dec 10, 2011)

Understood, the error must be on my part


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## nickvc (Dec 11, 2011)

I'm sorry if my reply seemed to be blaming you it wasn't my intention.
To develop trust with your buyer it really helps if you know what exactly your trading which is why so many of the US based members refine to as pure as they can get their product but here in the UK assays are cheap and quick and allows you to know that you are been treated fairly by your buyer, not all lower results are due to the buyer but sometimes are due to errors on our own part and an assay allows the truth to be evident as to where the errors are.


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## benign01 (Dec 11, 2011)

I didn't think you were blaming me. I melt and sell around £1 million per quarter of gold. I know what I melt, I know its cost and I know what I sell it for. I have dealt with all the big "refiners in the JQ" and I know who does what. There are honest ones and there are less than honest ones. However recently I have had some very odd results on low-gold content bars and hence I return to the beginning of this topic
The maths I have used to calculate the gold yield must be incorrect but the fact is I have had inconsistent results on the last few low-gold bars I have produced and it doesnt add up. I know what I put in, I know what the first few results yielded so why are the results now dropping. Indeed in one case the refiner zapped the bar, got 7.8%, redid it for no apparent reason and got 5.6% and then had an assay done and it came back 5%. The bar, based on previous results should have been 8% gold.

But as you say an assay will sort it out prior to selling, so problem solved


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## nickvc (Dec 11, 2011)

From your last post I can now understand your worries. To be fair an xrf reading from a gun that's been set for carat scrap buying means your bars at around 8% will not in my opinion get a decent result. If your source of material is the same each time and is identical I too would be extremely dubious of lowering results and if as I said the material is identical I would have individual pieces assayed as well to check it is exactly the same material been melted unless your paying on results.
If you leave a gap to be taken then maybe you will be hence as I said get assays and if you want to really be certain your been had get dip samples but don't say anything until you get the results from the buyer....could be interesting.
Ps if you need some glass rods to do this let me know and I'll see if I can scounge a few for free for you.


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## jimdoc (Dec 11, 2011)

I can't see how you could melt gold filled items into a bar in a way to get a consistent reading.
You are better off just refining it first.

Jim


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## nickvc (Dec 11, 2011)

It might not be gold filled he's melting but if he's using a purchased furnace it's almost certain to be an induction furnace and even if it's not with good temperature,fluxing and stirring he should have little problem achieving a good mix on every melt. 
Some don't want to refine as it takes time and a lot more labour, here in the UK as I have said many times assays are cheap and quick so it can be worth just melting assaying and trading.


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## benign01 (Dec 11, 2011)

Thanks for your offer, I have a few already though. You are right about getting each bar assayed beforehand though. Its just that the refiner I use doesn't rate the Assay office's results,which i find slightly odd. They prefer to use the company mentioned earlier,


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## benign01 (Dec 11, 2011)

jimdoc said:


> I can't see how you could melt gold filled items into a bar in a way to get a consistent reading.
> You are better off just refining it first.
> 
> Jim




Gold filled stuff doesnt give 8%. The stuff I have is now more like 1-2% No its a mixture of 9 carat scrap and gold-filed


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## qst42know (Dec 11, 2011)

Is it out of the question to do at least a nitric leach to up grade this a bit?

As it was explained to me 9k responds reasonably well to nitric as does gold filled.


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## Harold_V (Dec 12, 2011)

nickvc said:


> it's almost certain to be an induction furnace


If that be the case, stirring is a non-issue. The eddy currents developed in induction furnaces provide stirring that borders on being violent. 

Harold


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## nickvc (Dec 12, 2011)

I didn't phrase that as well as I could have Harold, thank you for putting into plain language what I was trying to say, that without an induction furnace good stirring would be highly recommended but with an induction furnace this would be done by the furnace itself.

If this material was mine I'd melt the gold filled as is and have an assay done on it and if the terms are low on this material simply grain it and add it in known quantities to karat melts to keep the charges down.


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## benign01 (Dec 12, 2011)

Stirring! Yes I stir and I stir and I stir, but only maybe twice for 30 seconds or so over the whole melt period! Can i ask Is that sufficient? Clockwise15 seconds then counter -clockwise. for the same period, two or three times prior to pouring. I don't have a fancy induction machine and nothing stirs if I don't stir it Done many melts!


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## nickvc (Dec 12, 2011)

With melting it's as much an art as a science, I find that the melts take on a very liquid look, almost like staring into a pond when the metals are all molten...that's the time to stir and feel what's occurring in the melt if you feel solids you need more time and more heat if on the other hand you feel the whole swirl then it's done but a good melt requires attention to detail and as I said any lumps in your melt means it isn't right and will require more stirring or heat...eventually you just know when it's time to pour the bar and if it's right it's like pouring water from a jug,smooth and silky and no lumps and the surface is clear and bright with heat rings been generated across the surface...I have always enjoyed watching molten metal it's almost alive and highly dangerous if not treated with thought and care.


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## DarkspARCS (Jun 28, 2012)

here's another thing to consider:



> The annalist was astounded by the amount of sulfer in the sample lol, which prompted him to reveal a lil device flaw the Xsort has, which is that the elements Iron and sulfer have the unfortunate affect of masking the actual ppm count for gold and pgm.


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## NobleMetalWorks (Jun 28, 2012)

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


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## Dan Dement (Jun 29, 2012)

benign01 said:


> I refer to my original question and add another
> Does an xrf analyser test differently if the gold content is relatively low eg 2%... What I mean is does the accuracy vary with lower amounts?
> 
> Any takers?



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


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## Lobby (Aug 1, 2012)

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.


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## Pauleames (Jan 23, 2013)

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.


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## fasTTcar (Jan 23, 2013)

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.


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## Dan Dement (Jan 23, 2013)

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


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## 4metals (Jul 1, 2015)

The moderators would like to thank all of the members that contributed to the original thread upon which this thread was based, as well as those that asked questions showing what was missing. Because of the extra length and interest in this thread we have created the above consolidated version making for an easier read. We encourage all members to read, comment, and ask questions in the original thread, The XRF Mystery.

The Library threads should not be considered to constitute a complete education. Instead, they're more like reading a single book on the subject of recovery and refining. There is so much more information on the forum, and it is impossible to include it all in these condensed threads. Members are strongly encouraged to read the rest of the forum to round out their education.


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