# Dental Scrap Techniques



## Coastalwasteus (Jul 7, 2018)

Hello all,

A little background:

I have been smelting (Induction melting) dental scrap for over 10 years, sometimes 14k Au and higher as well as mixed lower grade material such as dental PFMs and bridges which are a white/gray material and do vary widely in their content. I have years worth of assay data on the white/gray dental scrap. 

Recently I began refining my gold crowns with good success. The gold assaying around 99.89 % with a simple 2 step wash. This seems to be a pretty straight forward process to precipitate the gold and any Pd. Pt is usually in smaller amounts on the gold crowns and I usually just hold over the fluid in my stockpot since I have had little success. Note that even though I have had success with gold crowns, I have a lot to learn and I am sure I will stumble here and there.

I have read so many of the different items covered on dental scrap. I have read post after post and there is so much great information. I am still at a little loss on the best methods and procedures for refining white/grey dental scrap with mixed metals. AR? or Nitric acid boil first to remove base metals, then AR? I am concerned with a Nitric Acid boil to remove base metals as it may dissolve my PMGs, especially Pd. So far I am having some success in using AR 1:4 ratio Nitric Acid to HCL. Yes, all my base metals go into solution, but filter, filter, filter to a clear solution has shown good results in small tests. No larger tests have been conducted yet. I hope to have some done next week. Waiting on DMG, additional filters and so forth. 

I generally, even when I smelt, separate the dental scrap in three piles. 1) Gold Crowns, 2) PFM and Bridges that are white / grey and have flexibility and 3) Scrap that looks to be of no or very low value that is rigid or breaks when hammered. Again, while I am still learning and have much more to learn, I am getting proficient on the gold crowns for Au and Pd. 

I am trying to see if refining the white/grey dental is worth the time and effort over just smelting them. Understand that dental scrap varies all over, however I know my averages in each metal group when smelting in lots of 100g each and these average are very consistent for my region, so I will know once I refine them properly if it is worth the time and effort. The gold crowns are definitely worth the time, I get about 10% better return if I refine them to at least 99.9%.

Here is what I have done and I am going to repeat my small experiments and document them.

I have taken individual crowns and dissolved them in AR 1:4 ratio Nitric to HCL. That experiment itself validated how the dental scrap can look the same but is certainly of varying degrees of metal. (I have seen many posts with attachments that show the varying types of dental crowns and implants and the varying high Nobel and low Nobel metals.

A quick look at what I saw from individual crowns in AR 1:4 ratio Nitric to HCL

A) Gold Crown - Nice yellow solution. Clear. Test with Stannous solution showed nice black/purple for Au and showed Pd in a green with a little Yellow for Pt.

B) Small bridge - Clear green solution. Test with Stannous solution showed green Pd and some black/purple for Au.

C) Procelain Fused Metal (PFM) #1 (Picked at random). Showed again clear green solution with same results as B above.

D) Porcelain Fused Metal (PFM) #2 (Picked from Test E below). I picked this PFM because I knew it was different since it did not dissolve to any degree in Nitric acid.Got lucky and this tested with a red/orange clear solution. Test with Stannous showed dark purple Au and also dark green that from my experience would be Pd.

E) I ran one additional test as there are many here who say to rid this lower grade dental scrap of base metals by placing in Nitric acid. I placed a dental bridge and several PFMs into the straight Nitric. The acid went to work right away on the dental bridge and 2 of the 3 PFMs. One PFM was not getting any reaction. I waited until there was no more reaction. The one PFM had remained fully intact. The other two PFMs and the dental bridge dissolved almost completely with very small pieces remaining on the bottom of the beaker and some black powder. The fluid was a clear light blue solution. I must say I did not take good notes and need to run this test again as I do not know what the Stannous solution test showed.

I have a lot of tests before I start to try and drop anything from the solutions I have completed. I have several solutions that have come from several lots of dental scrap all of lower grade dental that I have dissolved with medium heat (145-154 F) in AR 1:4 Nitric to HCL. I have reduced all of it with medium heat (Approx. 145 F) to syrup and added HCL two times. I still have them concentrated and have not added any additional water. Each solution is varying in metals. Some show high Pd with low Au, others high Au with medium Pd. All show small hints of Pt. This is inline with what my assays show over the years.

I would love the opportunity to work with someone direct here that has experience in these type metals. Even some direction or guidance on information contained in this forum. I am happy to read as I have already read so many posts here and I am very familiar with Hoke. 

As you can see, I am in testing phase and no hurry to rush into dropping metals. I have been now working for 2 month straight on reading, testing and documenting low grade dental scrap. Sometimes I get tired and forget to document, but I will re-run those tests to have the results. I have read and used Hoke for my gold crowns which are 14K and above Au with Pd. I have very little problems there. This has helped tremendously in teaching me to read, run tests, validate and then once you gain knowledge and prove the theory, then and only then move on to larger lots. I am very well aware that this type of dental scrap is tough to process, but know with the right direction and performing small experiments to prove theory, that I will get this done properly. 

BTW. Kuddos to all of you who have put this site together. There is a wealth of information and great advice. I made the mistake a couple months back of working with an online company that sells proprietary branded powders that are alternatives to Nitric acid and also have their own precipitants. While it worked well with the high Karat Au, they have no experience in dental and not knowing what their chemicals were it was hard to research where things were going wrong on the low grade dental. I asked them about Hoke and the practically laughed saying it was old technology. That was the last straw for me. I knew where my problem was....them. Hoke is a MUST! It teaches you so much in the basics and then hands on tests and results that each beginner needs to see and experience for themselves. If you read and read again and again until you feel comfortable to perform some of the outlined tests, you will find that you will have most of your answers when you run into problems based on the tests you did.

Thank you all in advance for your assistance.

DC


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## Coastalwasteus (Jul 7, 2018)

I thought I would add some pics from Test D

I like to do both a clear spoon for the AR sample and white filter paper. Both help provide more information on what may be in your AR.

So this was from what is known in dental as high Nobel PFM (Porcelain Fused Metal). You really can't tell when buying them which is which because they are really all a dull gray metal. Most will not return this type of result.

I also did a test with a few Copperas in a drop of AR on the clear spoon. Gold precipitated immediately out and left a nice small amount of gold on the spoon. 

I will try to drop all the gold tomorrow in this solution and then retest with Stannous Chloride to see what remains. I expect Pd and some Pt. I think the gold will drop without issue.

I am wondering if I should leave the solution condensed or add water before adding Copperas tomorrow? Thoughts?

Thanks again.

DC


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## Coastalwasteus (Jul 7, 2018)

Last picture did not fit. Side-by-Side picture of the direct drop of AR on white filter paper and the drop from the clear spoon, both with Stannous Chloride. Notice the difference, that is why I always do both.

If you watch when you first put a drop of Stannous Chloride on the sample from the clear spoon you will see the different colors immediately and then they blend together quickly into one color. The white filter paper really helps show the several metals.

DC


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## snoman701 (Jul 7, 2018)

Your post leaves me with more questions than answers. 

You have said that you are smelting dental. 

Are you willing to share exactly how you've been "smelting"? 

Are you melting your Pd porcelain crowns? 

Are you directly dissolving a crown in AR, or melting it in to an alloy with copper first? 

What are you then using to precipitate your gold from the aqua regia? 

What kind of quantity are you selling at a time? 

What are your goals for processing yourself? 

What I can tell you is that most of the answers are on this site, but you will have to dig a little. If you study the platinum group metals forum, you'll find that there are posters there that are very knowledgeable. 

Of course, safety....platinosis...do your reading and please practice excellent housekeeping and keep in mind that any visitor to your lab is potentially exposing themselves to platinum salts. If you have been processing platinum alloys in acid for ten years, you may be ok, but they may not be so lucky. But more than platinosis, how are you handling the latent mercury threat that exists with all dental? Hope your ventilation is top notch, and your waste disposal is ongoing and monitored.


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## Coastalwasteus (Jul 7, 2018)

Hi Snoman701,

Thanks for your reply. I tightened up some of my wording on the original post.

Maybe I am not using the right terminology. If so, I apologize for the confusion. When I say smelting I mean melting the dental scrap with borax into a bar. I hear many people define this as refining, however I believe refining is the process that this forum is all about. Bringing the metals to their pure form via chemical separation. This is not my primary business, yet I am well versed in dental scrap from a smelting (melting) standpoint. I am also fairly proficient in refining gold crowns in AR which tend to yield 62% Au or higher.

When smelting I do separate the dental into three categories - Gold crowns, PFMs & Bridges and scrap that looks to be of low value. This takes experience in knowing what scrap is good and what is not, yet still not the best way. A hand held XRF machine is best.


I do not like to use copper when smelting to homogenize the bar. It lowers the Au% and you get paid less when selling on the market because of the low percentage gold. You also won't get paid on Pt as it lowers all precious metals. Gold crowns always melt together without any other dental scrap. 

I actually moved to dissolving the crowns in AR 1:4 ratio of Nitric to HCL and precipitate the Au with Copperas and the Pd with Sodium Chlorate. I find that I get a better return on gold crowns with Refining over smelting. If smelting I always hammer off the ceramic from the dental scrap prior to a melt. Less borax is used and you also get a sense of what type of scrap it is. Brittle is a key that it is very low grade. Super hard could mean Pt/Pd but not always as there are so many metal like Chromium, Nickel or cobalt. Generally three categories of metals used. High Nobel, Nobel and Non-Nobel. Of course you want High Nobel.

I just started to conduct tests on the other two types of dental scrap which are both lower grade metals. Pd normally runs the highest in this type of scrap. Still learning so I have little to offer besides my tests which I began posting. 

Hoping others who have been down this path can assist. While I am fairly new to refining I do read a lot and conduct small tests prior to performing it on any larger batches. So far things have been coming out good but would love to hear from those that have travelled this path. My primary business is Medical Waste and Hazardous Waste, so I tend to error on the side of caution. Not to say that I won't step into doo doo but I definately will minimize my exposure.

My goals are to analyze the refining process of Nobel dental scrap which is the second category of dental scrap (i.e. what many call white or gray dental scrap). I want to process (refine) some small batches of this lower grade dental scrap and do the math on the returns vs just smelting and selling it. It may turn out that it is best to just smelt and sell, but I want to see that for myself.


Thanks for the heads up on the Platinosis! I am well ventilated. The 10 years smelting has been done in a professional setting with a proper hood and exhaust ventilation. I am doing the refining in a smaller shop with no exhaust or hood but good ventilation. I will read more on the subject and be careful. Thank you. 

On the subject of mercury, yes anyone who does not know or understand dental scrap places themselves at risk with mercury as well. The only mercury used in the dental industry is in the form of amalgam. Amalgam contains silver and tin but also has mercury and is used in fillings. If you are processing extracted teeth with amalgam fillings, non-contact or contact amalgam, amalgam waste or dental traps (filters) which do contain all dental metals from a dentist office and are used to collect material when a dentist is removing filling, teeth, crowns, implants and so forth, I would recommend taking caution as it does contain mercury and the mercury needs to be retorted prior to working with the metals. PFMs, Onlays, Inlays Crowns and bridges do not have amalgam, not even in the cement they use to secure it. Make sure you clean your dental scrap well before working with them. Either soak in bleach or I use Cavacide1 which kills many infectious diseases. Note taken though and great advise. Know what you are working with if you choose to refine.

In my refining, I may cement out the PMGs with a copper bar after I precipitate the gold with Copperas as I have heard from others that this is a safer method, yet I have not heard what percentage copper cementing yields? 

Hope that helps. DC


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## Palladium (Jul 8, 2018)

Welcome to the forum!

Smelting is what is done to raw ore. Melting is what we do.


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## nickvc (Jul 8, 2018)

Dave.
As I posted on your welcome in thread refining PGMs is not something to be taken lightly.
Without a hood and proper extraction your are taking serious risks as platinosis has no upper or lower dosage limits to cause permenant and extremely serious health issues any inhalation or skin contact can begin the process that is irreversible. 
I’m not saying you can’t do this as I think you can with reading and study you can but take note of the health warnings and install a hood and extractor and use good gloves when handling any solutions or solid salts.


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## Coastalwasteus (Jul 8, 2018)

Hey Nickvc,

I will definitely take your advice and read more about PGM salts, solutions and Platinosis. My experiments have been very small, less than 5 dwt of dental scrap. The solutions I have processed to a syrup have been done in complete open air environments. I do appreciate your concern and will read more on this subject. 

I will go back and search the forum to see what has been posted and see what has been listed in the safety and chemical sections as well as google information. Your warning is heard clearly and I thank you!

DC


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## nickvc (Jul 8, 2018)

Dave with your attitude I’m even more sure you can do this but you do need the proper lab set up and to fully understand the risks, the rewards could well be worth the cost and effort, there were several threads many years ago covering a member who was processing this material who built a closed system and atomized the material to make dissolution easy and without using nitric, I believe 4metals was involved in the thread with his usual incite and clever thinking, if you can find it it may help you.


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## Coastalwasteus (Jul 8, 2018)

Thanks again Nick,

I have been reading a lot and certainly Platinosis is not something you want to get. I do have about 20g of red salts that are wrapped in a paper towel and in an air tight container that I precipitated in the full outdoors. Today I did a little experiment with Ammonium Chloride on a solution I was confident had Pt based on Stannous Chloride tests. I had already reduced it and added a small amount of HCL. The Pt drop was successful on a very small sample. I was wearing gloves and the Pt salts were wet and very small amount. I think I may head the copper cementing way as I learn more.

From what I have found and read so far, the PGM salts are the biggest concern. I would think any AR or Nitric solution containing PMGs would give exposure with both fumes and skin contact. 

Personally I do not have a need to precipitate in the form of PGM salts, either Pt or Pd. I would be happy with a metallic form. So, if I drop my Au from the AR and then cement out the PGMs with a copper bar, it will cement out in a black powder that I can melt to a PGM bar? I don't mind it is Pt and Pd combined.

Thanks again for giving me a heads up. So much reading on process, chemical exposures, chemical reactions that you sometimes forget about the salts themselves that you are producing. I appreciate anyone pointing out something of concern in a persons procedures.

DC


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## snoman701 (Jul 8, 2018)

Smelting generally refers to a technique in which you concentrate one material by chemically changing another. So in the case of mined ore, you concentrate say, copper, by oxidizing tin, lead, iron, etc into the slags. 

Smelting dental can be done, and it has it's place. 

The mercury threat is not only from the traps. Often, if your dentist is a little careless, they can leave a small piece of amalgam filling on a tooth prior to installing the crown on it. It's not something that happens all the time, but it's frequent enough that you should be aware of it.

Platinosis is a tricky disease. When you are first exposed to the Pt+4 ion, your body reacts to Pt+4 ion to form a specific protein that is seen by the body as an antigen. The exposure to this antigen triggers the body to create antibodies. From here on out, it acts like a bee sting allergy...each exposure has an ever increasing response. The problem is, the exposure is to residue as well as the bulk chemical. Lets say you are working in your lab and normal handling of the platinum salts transfers minute amounts of residue to your clothes. Then you go home, without changing, and you transfer it. Now you have contaminated not only your lab, but your home. You will never clean the residue from your home. So now you have an environment that is always triggering your disease, and you can't escape. 

The good thing, not everybody who is exposed to platinum will develop platinosis. The bad thing, you have to be exposed in order for your body to start making the antibodies...and after that, you are already hooked on refining.


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## Coastalwasteus (Jul 8, 2018)

Thanks Snoman.

I appreciate the additional feedback.

DC


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## snoman701 (Jul 8, 2018)

You said you are seeing an increase of up to 10%, and I just don't understand those numbers....that is, unless you have someone who's paying you over spot! If not, you need a better outlet for your gold. You should be able to sell your gold crowns and bridges on a 4 metal basis for 98% of spot on the gold, and 85% of spot on the other three.


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## Coastalwasteus (Jul 8, 2018)

Snoman,

Don't take this personally, but I really don't want to debate profits and losses with you. If you want to add value with refining on safety, procedures or anything related to refining, please do. Other than that you are just adding more text people have to read that is not relevant to this forum. 

I have read so many threads and cannot believe the responses people give that are of no value to refining. This is a great site. Stick to the forum.

I am happy to take critique in my safety, my procedures or any advice that helps me, but rambling on off subject helps nowhere. 

Dc


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## Palladium (Jul 8, 2018)

Not everything you consider rambling is such. The value of even the smallest tidbit can be invaluable to some.
That's kind of like restricting speech to what is viewed as only relevant to a select group. Folks are more than welcome to ramble as long as it's related to the forum purpose. Yes it gets off topic, but theirs value in open discussion and even constructive debate. With that said why would you not think prices would be a topic of discussion? I only seen him trying to offer advice freely. You seemed overly offended about that.


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## Coastalwasteus (Jul 8, 2018)

Thanks Palladium. I have nothing to add. Besides safety, which I thank Snoman.. he has given no advice on dental scrap.

This is not a business forum and frankly I don't have the time to debate him about my profits

I apologize, but I came here to learn about refining. The posts about safety are very welcome..but all this debate off subject don't help and give way to so many threads that don't train on refining. 

I belong to other forums on topics that are not refining. The moderators quickly delete off topic responses. It helps keep the forum clean on the subject people come to the forum for.


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## FrugalRefiner (Jul 8, 2018)

Dave, you might want to spend more than a few days here before you tell people what they can and can't post. Members give their advice freely here. If you don't find a reply helpful after you read it, just move on. If you criticize replies, you will soon find that you won't get any.

Dave


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## Coastalwasteus (Jul 8, 2018)

Fair enough and well said. I will take that advice.


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## snoman701 (Jul 8, 2018)

I ask about your sales and quantity because it's a very material question. If you are trying to process gold bridges and crowns to increase their value, it's a losing proposition, especially if it's only a hobby. Sell it direct to metalor or midstate. You'll get fair payment on all four metals, with 98%+ on gold. I've seen the mess created when people think they know what they are doing trying to process the pgm's without appropriate housekeeping and without appropriate safety. 

If you had replied and told me that you are selling 50 oz of high noble dental a month, I would have sent you a private message telling you who to contact to get you set up. 

As it is, I'm still not sure if you even have a closed ventilated lab safe from cross contamination that causes exposure to kids and the like, or if you are doing this on a picnic table outside in a public park. 

Since you are crying that I'm not giving you enough information about refining...

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?t=11599

Now you have reading material. Go read it. I'll tell you that I've read a lot of the forum, the gems are hidden. The above thread is a gem.


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## Coastalwasteus (Jul 9, 2018)

Thanks Snoman, 

This is the kind of stuff that helps. Not trying to be hard on you, just so much to read, learn and work with others that I don't have time to go off subject..

Btw.. not a hobbiest. I appreciate your feedback on just selling to a refiner, but I would like to see the results for myself. I will do small lots and the numbers will tell me everything I need to know.

Thanks again 


Dc


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## Coastalwasteus (Jul 9, 2018)

Snoman,

I read the link and I can tell you that I am not equipped or want to be equipped to go that far with PGMs.

I will look into cementing the PGMs with a copper bar. Any thoughts on that?

All I really care about is getting rid of the majority of base metals and separating gold from PGMs. So pure gold and a separate mixed PGM bar is fine with me. Even if the PGM drop has some base metals.

You may already know the answer, but I want to lab test it and see it for myself. Will my returns be better if I drop Au and separately drop PGMs, vs just induction heating the low grade dental scrap.

I may not even continue once I see my results. But I will get these tests done to validate. It has always been on my mind.

Thank you


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## anachronism (Jul 9, 2018)

Let's be blunt here. 

Amazingly experienced PGM refiners even on this forum have DIED. Yes you read that correctly. Dead- no going back from that. An old friend of mine who is on this forum and is 70 laid it out hard and fast to me. He said "I deal in gold and silver and my friends who refined PGMs were all dead by 60."

Think about that long and hard when you suggest people are rambling. 

All my PGMS- and I do quite a lot per year, go to specialised refineries, because to use the base language- I am going nowhere near that sh*t.

Take the advice or leave it that's your choice. There are ways to get PGMs out in metallic form and send them for further processing without messing with salts. 

The idiots who do these in a home environment think they are clever. They are not.


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## snoman701 (Jul 9, 2018)

Coastalwasteus said:


> Thanks Snoman,
> 
> This is the kind of stuff that helps. Not trying to be hard on you, just so much to read, learn and work with others that I don't have time to go off subject..
> 
> ...



The thing about the reading is that if you try to focus on one aspect, you'll miss another that has the very real possibility of influencing the results. 

Have you considered sending off a sample to someone like Lou who can tell you exactly what's there, without the danger of exposing yourself to the PGM's? The cost isn't that expensive in comparison to the time you'll invest.


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## Coastalwasteus (Jul 11, 2018)

Anachronism,

No debate on your post. I have already posted that I will be cementing the PGMs in metallic form. Even if I changed my hood at the office to accommodate refining the PGMs, I just don't need the PGMs pure and don't need the additional safety issues.

I agreed with all that have posted the safety issues with PGMs, there has been no debate from me there. The earlier reference to rambling had nothing to do with PGMs, safety or refining. 

It's all good.

Appreciate everyone's concern.


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## nickvc (Jul 11, 2018)

Remember when you dissolve any PGMs with acids you produce salts so even the solutions are toxic even if you cement so bear that in mind before processing any scrap and take appropriate safety measures, the real danger of platinosis is its cumulative and you won’t know you have a problem until you do :shock: :twisted:


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## Dr. A (Jan 31, 2022)

I’m not refining yet by any means, but saving certain scrap to do so. I have not refined dental scrap, BUT I have turned in A LOT over the years as a dentist. Yellow dental scrap is desired, of course. But don’t underestimate the value of the PFM (porcelain fused to metal) scrap. I send mine to Garfield Refiners (5% processing fee, that’s it), they melt and assay the lot. The majority I turn in is PFM and I’m surprised at the Au and Pd values and there’s always a little Ag and Pt too.
There is high noble white metal that is minimum of 60% high noble metals with a minimum 40% Au. There is noble metal alloys which can be 40% of any high noble metal, usually quite a bit of Pd, which used to be very cheap 20+ years ago. Then there is base metal crowns which can have some precious metals (0%-40%), but are mostly Ni, Co, Cr, etc.
Anyways, until I get into refining, these are a great source for extra cash, or they send me bullion or coins in return.

Dr . A


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