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

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.

benign01 · Dec 7, 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.

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???

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?

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

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.

benign01 · Dec 8, 2011

qst42know said:
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.

I give up!! i didn't want advice i wanted answers...never mind!!!!!

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.

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?

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.

benign01 · Dec 8, 2011

Thanks Nickvc.

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?

shaftsinkerawc · Dec 8, 2011

Send me an XRF handheld and I'll run some tests for you. If you have a university near you they would probably be able to help.

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.

benign01 · Dec 8, 2011

bryantch said:
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.

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%??

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.

benign01 · Dec 9, 2011

nickvc said:
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.

.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?

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.

benign01 · Dec 9, 2011

4metals said:
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.

Very very useful, many thanks

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?

:?:

The xrf Mystery

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