Coastalwasteus
Member
- Joined
- Jul 5, 2018
- Messages
- 15
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
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