Silver purity in hand poured bars, Sigma & XRF testing, Fine Silver Shot vs. Bullion for melt, (AKA a few questions/discussion from someone newer to pouring)

[WeekendJail]

Hello, everyone, 

This is my first post here aside from my introduction post, so if this is in the wrong section please let me know. 

I am in the U.S., IDK how relevant this is, but yeah. 

Anyways, myself and a buddy of mine have been making our own hand poured bars and rounds for a couple months now (on and off)-- and it's turned from a hobby into a bit of a small business, primarily making custom bars for friends. For example a bar with a custom stamped message for an anniversary gift, that kind of stuff. 

i was curious for those who either make their own hand-pours or collect a lot of hand-pours about purity and testing.

When I had first looked into this I was pretty shocked that people on various other places (subreddits, etc) say they have poured and sold many pieces without ever getting anything tested. Is that common, or am I just getting a weird sample? 

So-- short story:
When we had first started pouring bars (high density graphite crucibles, and molds) I had taken a few to an LCS along with a few hand poured bars from pretty well known companies. 
I got readings all over the place from sigma machines (I do not own a sigma machine, myself, as I am what you would call "working poor")-- one LCS said they were fine silver, one said they were not even .925, after a post-sigma "fail" acid test which was done out of my line of sight which I knew could not be the case; so I feel like the second place was just trying to get me out of there as they were extremely busy, and the guy had an attitude for the the first moment. (Keep in mind I brought in a handful of bars from different companies as well, so giving them the benefit of the doubt, maybe their machine was not calibrated correctly and/or the acid had gone bad as I had tested it with acid myself and all good on my end). 
So I went to a pawn shop with a sigma machine and had the same thing happen to me (minus the "bad" acid test.. they did one but it came up as "at least .925"), this includes the other bars tat I did not make. 

So I took all of the stuff to a huge pawn shop a bit out of the way that I knew had an XRF machine and everything tested as it should (.999 fine or higher), as well as a guy doing a favor for me and sending one off in his batch to get assayed, as I do not have the volume for local refineries to work with me, and that bar came back as being fine silver. 
*story over* 

So I thought this was all sort of odd. 
I looked a bit more into how sigma machines actually work and found some anecdotal evidence that they can be finicky with hand poured silver. 

Was wondering if any of you guys have had similar experiences with sigma machines? 

the main worry here is if I sell someone something, they take it to a sigma and it doesn't test right. So, obviously not a good thing to happen, but I'm not sure how common this kind of mismatch is with testing, or if the guys just wanted me out of the shop for some reason, etc.

I was very much taken back when the guy told me the sigma was not reading it as fine silver as I know I had melted down fine silver from a reputable dealer, no other metals in the crucible or molds-- but then taking the exact pieces to get XRF tested and they come up as fine silver (plus the bar that was drilled and assayed coming up as fine silver)... it's just odd to me. 

I guess subject number 2-- as far as melting down silver shot/grain vs bullion bars/rounds. 
I've bought some silver shot from two different reputable sources, and I have also melted down "bargain bin" silver rounds-- both test at least .999 on the XRF test. 

I was curious what those who pour generally use or prefer, and why? 
I see most shot is labeled "999+" which I gather is at least .999 fine, but could be more fine. Is that pretty much the gist of things? 
I can generally get 999+ shot for a bit cheaper than melting down rounds, though it's not a huge difference in price. 
Does it really make a difference? 

I guess I'm just interested to hear any input about the stuff with the Sigma and XRF tests, as well as with the Silver Shot versus Silver bars/round for melting. 

P.S. Sorry if this sounded like a bit of a ramble or a bit disjointed, for some reason wording this was a bit hard to keep concise. 
Any input/discussion on these topics would be greatly appreciated. 

 

 

[CANV]

Backyard Bullion  has a you tube back catalogue of excellent videos, he may have something on this .. I know he sends his stuff off for hallmarking In Edinburgh in think?

adds to costs but looks great and gives the customer the security they want 

[WeekendJail]

11 hours ago, CANV said:

Backyard Bullion  has a you tube back catalogue of excellent videos, he may have something on this .. I know he sends his stuff off for hallmarking In Edinburgh in think?

adds to costs but looks great and gives the customer the security they want 

Thank you for taking the time to respond. 

I remember seeing that video on YouTube about hallmarking from BB awhile back (before I started doing m own pours)-- but I am in the United States and as far as I can tell we don't have the same type of system that I know of. 
I've called refineries & assayers which do something similar but their minimum amounts for assaying are all around 15 to 20 kilograms of silver (at least the ones in my State). 
Which I do not have that kind of volume, maybe if I wanted to use my entire stack, but that would probably come to just under the minimum. 

It would be great to find a place here that deals with lower volumes of silver. 

[ArgentSmith]

It could be you have used a fake or contaminated coin/item in your melt or a pre 2013 Britannia which weren't 999 Ag. Potentially a contaminated crucible, of even small amount of iron from tools or fillings. Possibly surface contamination from a rusty anvil.

The first silver I poured was .925 all from British hallmarked items. None of that batch tested good on the sigma. With hindsight I believe it was either contaminated with solder or a steel pin or hinge found its way into the pot.

 

Edited April 27, 2023 by ArgentSmith

[Arganto]

Lots of Simga users on here, hopefully they will offer their experiences. As far as I understand it XRF scanners are a more 'thorough' test of composition, giving you the percentage amounts of each element contained in an item within a range of accuracy. If a patient XRF operator (there is a minimum time required for an accurate scan I believe) has analysed your items and recorded high purity silver it does infer that the Sigma operators made mistakes or used out of calibration machines. The acid test performed should have been more accurate than the ~7% margin of error also. 

How thick are your poured bars?

[WeekendJail]

On 27/04/2023 at 04:39, Arganto said:

Lots of Simga users on here, hopefully they will offer their experiences. As far as I understand it XRF scanners are a more 'thorough' test of composition, giving you the percentage amounts of each element contained in an item within a range of accuracy. If a patient XRF operator (there is a minimum time required for an accurate scan I believe) has analysed your items and recorded high purity silver it does infer that the Sigma operators made mistakes or used out of calibration machines. The acid test performed should have been more accurate than the ~7% margin of error also. 

How thick are your poured bars?

They are, up to this point, less than 1 inch thick. I'd say most are somewhere between 10mm and 15mm in thickness. 

[WeekendJail]

On 27/04/2023 at 00:41, ArgentSmith said:

It could be you have used a fake or contaminated coin/item in your melt or a pre 2013 Britannia which weren't 999 Ag. Potentially a contaminated crucible, of even small amount of iron from tools or fillings. Possibly surface contamination from a rusty anvil.

The first silver I poured was .925 all from British hallmarked items. None of that batch tested good on the sigma. With hindsight I believe it was either contaminated with solder or a steel pin or hinge found its way into the pot.

 

The only thing I could think of was some sort of carbon contamination from the graphite? Then again sigma is the only test these pieces failed.  
I'm going to be pouring another batch in a few days (I've since cleaned up a bunch of dirty tools and whatnot... it seems that the stamps and anvil were quite dirty). 
I now have a tumbler, steel shot, burnishing solution for polishing so that should hopefully take off any surface contamination. 

Been using high density graphite crucibles in a propane furnace, so I don't know what kind of contamination might have taken place there, HOWEVER...  

...all tests aside from the sigma came up good (i.e. 999 fine or more pure by various different testers)-- XRF, assay, acid, specific gravity (home test, which is enough to know it's silver but with just water, string, and a scale I think there's too much of a margin or error in the home specific gravity test to tell the difference between 999 fine and 997 fine). 

This whole situation with the sigma tests was a few weeks ago-- so with the new pours that will be done in a few days we shall see.

The initial bars were make out of some fine Silver Shot (labeled 999+), aside from two made out bullion which were melted down (one 999 fine, one 9999 fine). 
This makes it extra odd, because if the sigma is correct (and the XRF & others, including one other sigma test; are not correct somehow) the bars being tested were made from 3 separate batches of materials... so it would be unlikely that the silver itself from 3 separate places were all contaminated.  

I guess we shall see, but it seems (especially with how many people are panic buying silver lately here) that the shops are super busy and are not taking their time to see if the machines are calibrated correctly, I don't know if they even changed the settings on the machine from my point of view. Everything was done very quickly. 

Also-- with some of the shot being labeled 999+, let's say it comes out to being 9992 fine... will a sigma just not read that? 

IDK-- I have far more questions than answers with this whole situation. 

but like I said-- going to be doing some more pours soon, and most are going to be some 999 rounds from the same manufacturer and I suppose I'll separate those bars from whatever other fine silver I'll be melting down, get them XRF tested again and see if I can find a place with a sigma that will give me the time of day.