Nitric acid alternative for dissolving gold?

[Will Robertson]

Originally Posted by Pete VanderLaan

Both Arsenic and Antimony flip valences on the outer ring at differing temperatures but make both very useful in squeezing glass melts. Arsenic is not used so much now since it was more useful in lead based glass

Are there any other elements or species that change valencies at different temperatures in glass melts?

Originally Posted by Pete VanderLaan

Go to Monterrey Mexico and you'll find a very slick lead glass factory.

Is that related or not to the site in Tijuana, Mexico where Oceanside shifted Uroboros production after shutting down Uroboros in Portland?

[Josh Bernbaum]

Originally Posted by Will Robertson

Are there any other elements or species that change valencies at different temperatures in glass melts?

Chromium, maybe Selenium too?

[Pete VanderLaan]

Antimony and arsenic are ( to the best of my understanding) the only metals that will switch valence but not color the glass. Otherwise. there's lots.

[Will Robertson]

Originally Posted by Pete VanderLaan

Antimony and arsenic are ( to the best of my understanding) the only metals that will switch valence but not color the glass. Otherwise. there's lots.

Would I be right in guessing that that valence switching behaviour allowed the old arsenic recipes to be oxidising at high temperatures which helped metal oxides to dissolve more easily in the melt then - almost by magic - flip to being slightly reducing at lower temperatures which encouraged colloid formation?

[Pete VanderLaan]

No. No not at all.

[Will Robertson]

Originally Posted by Pete VanderLaan

No. No not at all.

What changes does the valence change of As and Sb on cooling cause to the melt? It will cause a corresponding opposite change to other metal ions - contributing or removing an electron to/from their outer shells?

That alone would be expected to change the colour of coloured ions but in some cases would it also change the shape of the outer shells, changing how/where they fit in to the glass matrix?

[Pete VanderLaan]

Take a gather of a good hot clear glass that is bubble free sometime and shoot a stream of compressed air at the gather for about thirty seconds. Then stop the air and what do you see happen? It's a multi step observation.

In glass, all these metals are affixed to an oxygen atom Si isn't Si, It's SiO or Si02. Add up all of those oxygen atoms in any formula They begin to add up to a real weight portion of the glass, 10 to 15% would not be out of the question but the glass is clear. Where are they?

They're in solution in the glass and you need to ask yourself how that can be? After all, the glass was a frothy mess when it was being melted. Did they really all rise out of the mess?

That compressed air will tell you where they are and examining valence switches and the temperatures they switch back and forth at are equally telling.

As I said, spend more time with the stew, the goop whatever you choose to call it. When I teach I don't like thinking about stuff which my eyes can't see. I want people to use their senses and to use the brain they were given. I don't know of any single book that assumes you know nothing and that it will teach all. The books I refer to are for engineers in studios. The term engineer in our world is known as the shop tech and that person fixes all the problems that used to be handled by the students before the insurance industry swept in. we learn in degrees. One solution leads to another problem which leads to another solution.

The reason the archives are so valuable here is that that is exactly what they do. Threads start in one place and wind up unexpectedly in another. There are years of experience here in those archives. Over 100,000 posts. I haven't seen a question from you yet that the archives has not broached. All of the books that are out there are all missing puzzle pieces or are puzzles with some missing stuff. There' is no "Book".

What Henry put together is a compendium of issues that others knew way better than Henry. The fourth Edition is the apex of that but the early ones were godsent . Some of us went into casting, some to blown ware, some to the basic chemistry itself. All these directions. Henry with his compendium brought us together in a concentrate.

You're right in a sense that things have changed mightily in pursuing success with this stuff. When I wrote the section on Batch glasses Henry said I was the only one willing to share knowledge who knew anything. That's not wildly inaccurate but I find the world much changed from when I wrote that chapter for him. I wanted ten times the space but so did everyone else. Now, Buying those chemicals can be very difficult. All the original sources I had are pretty much gone. Retired, dead, indifferent but not available. When he asked me to do an update I responded that the world was much changed and I could not explain the "how to" easily at all. .

All those verboten colors are still being melted I note but sourcing materials has become more secretive. It can still be done. I do it. I see people on this board doing it but they aren't going to offer up the moon to you, especially if it makes things harder for them. The archives and the books mentioned are all there to read.

Now you need to figure out what is happening with that compressed air.

[Will Robertson]

Originally Posted by Pete VanderLaan

Now you need to figure out what is happening with that compressed air.

I don't have an air compressor - just use the compressed air line in friends workshops whenever its needed - there's not much space up here.

Hopefully the high temperature refractory bricks and materials to make high quality Zn- Ba SiO2 glass will be here in a few weeks - until then it's just recycled window or packaging glass (a semi-pet woodmouse is playing in my basin of ground-up glass at the moment).

I can try to work out in my mind what will happen - independent of the batch chemistry, the glass on the outside will cool and contract fast, squeezing the still-liquid glass on the inside - after that the glass on the inside will begin to cool and contract as well - as it all goes rapidly below the annealing point the internal stresses set up as the glass continues to contract but cannot flex may cause the glass to crack and take on a crazed appearance?

[Will Robertson]

Originally Posted by Pete VanderLaan

Antimony and arsenic are ( to the best of my understanding) the only metals that will switch valence but not color the glass. Otherwise. there's lots.

What about tin in colloidal colours? Sn is colourless but Weyl seemed to reckon that the transition from Sn(II) to Sn(III) was critical to the formation of copper and possibly gold rubies.

As Cu(II) gains an electron or two to become the Cu(I) or Cu that form the ruby colloid something has to donate that electron - tin changing from Sn(II) to Sn(III) would donate that electron.

What about lead? We've talked a lot on the forums about whether Pb is critical to the formation of gold rubies - could the transition from Pb(II) to Pb(IV) play any role in this? The Pb(II) to Pb(IV) transition is more difficult than the Sn(II) to Sn(III) transition - maybe this could help to explain why seems to be able to do some things that other metals can't? Perhaps this may be a role of Pb in the Au(I) to Au transition in gold ruby formation?

(The above re. Sn is an oversimplification - there appears to be research suggesting that Sn also plays a more subtle role in formation of nucleation centres around which Cu and Au nanoparticles form.)

[Pete VanderLaan]

It seems to me that this approach tends to cause intimidation for anyone wanting to make a copper ruby. The simple reality is that Sn0 ( black tin) is extremely effective in reducing ( taking an oxygen) another material in the melt. In the small studio, it's really what you need to know.

Keeping materials that drag along excess oxygen into the goop just cause trouble. It's where, Potassium is extremely desirable in making a good color in the ruby is best gotten from Potassium hydroxide ( KOH), not potassium carbonate (K2 C03), The simple point being, keep the O2 to a minimum, use red copper Cu20) . and you'll likely get a nice red. Weyl is a tough read and I think it makes understanding what to do more confusing in many instances, not less.

You still need to get that compressed air on the hot glass. Look for terms like "Reboil" OR "Squeeze".

[Will Robertson]

Originally Posted by Pete VanderLaan

Keeping materials that drag along excess oxygen into the goop just cause trouble. It's where, Potassium is extremely desirable in making a good color in the ruby is best gotten from Potassium hydroxide ( KOH), not potassium carbonate (K2 C03)

Thank you very much. I think I'd read somewhere that the excess oxygen in carbonates just bubbles off as CO2 - doing more study based on your words I realize now that that is not the case - in alkali glasses it stays as carbonate in the glass and in silicate glasses it forms CO2 molecules which can form a supersaturated solution in the glass and may be released as bubbles only slowly... 🙈🙈🙈 Using KOH sounds a very good way of avoiding both these complicated and undesirable situations.

Would I be right in thinking that instead of the Na2CO3 and K2CO3 in the 2013 Guadalupe Unoxidised Clear and Guadalupe Zinc Base you'd now prefer NaOH and KOH?

Originally Posted by Pete VanderLaan

The simple point being, keep the O2 to a minimum, use red copper Cu20) . and you'll likely get a nice red.

Thank you very much. When I started out I somehow got the idea that a glass was either reducing or oxidising and that I could be fairly ham-fisted with oxidizing and reducing agents - am I right in thinking now that the redox state of glass is very sensitive and something that I need to carefully protect - even additions of oxidising or reducing agents on the order of 1% can upset the balance?

Originally Posted by Pete VanderLaan

Weyl is a tough read and I think it makes understanding what to do more confusing in many instances, not less.

Weyl is great for anyone who wants to study the history of glass chemistry but for anyone who just wants to understand glass chemistry and not the history of glass chemistry it can be hard going...

Originally Posted by Pete VanderLaan

You still need to get that compressed air on the hot glass. Look for terms like "Reboil" OR "Squeeze".

Is it a commercial soda lime silicate glass (which I'd expect to be chemically fairly dirty - containing substantial Fe contamination from Fe in the sand, chemicals added to reduce the visual appearance of this Fe and fining agents including probably sulphates 🤢 ) or is it a high quality art glass which I'd expect to be much cleaners - made with high quality low-iron sand, no addition of sulphates, roughly equal amounts of K and Na (and perhaps Zn and Ba in lead-free crystals)?

Was away climbing over the weekend and realized that during my training in chemistry I learned to talk in riddles - when a chemist says that an ion has been "oxidised" they mean that it's lost one or more electrons - oxygen may be involved - as it is in glass - or may not be involved at all. That must make it insanely confusing for any non-chemist who hears a chemist talking about "oxidation", "reduction" or "oxidation states"... We learned it at school as OIL RIG - Oxidation Is Loss of an electron, Reduction Is Gain of an electron. Hopefully that helps any non-chemist who's reading this and is understandably confused 🤪.

[Pete VanderLaan]

Jeez, go melt a few thousand pounds of glass.. get back to me then but not before please..

[Will Robertson]

Originally Posted by Pete VanderLaan

Jeez, go melt a few thousand pounds of glass.. get back to me then but not before please..

Given that I live on a mountainside where everything has to be carried in and out up a fairly steep track on my back I don't think that's ever gonna happen.

It's important to get these things right and get your views on things because there are a lot of books, "conventional wisdom" and other sources out there that are either confusing or misleading.

What are your thoughts on Introduction to Glass Science and Technology by James E Shelby? To me some isolated parts seem of use but overall very theoretical and not particularly relevant to what we're doing?

[Jordan Kube]

Do you have the 4th edition of Glass Notes? Pete wrote a whole section on glass melting. It's available for download.

You're up on a mountainside, so I'm guessing you're not going to really want a pot that holds more than 15-30 pounds. At lest that's all I'd want to carry at one time. Dave Bross has some decent clear recipes posted here. The point Pete is trying to make is you can talk about swimming all you want but at some point you're going to have to jump in the water. Believe it or not the glass making is the easiest part of this whole thing.

[Pete VanderLaan]

The utility bills are the hard part.

[Will Robertson]

Originally Posted by Jordan Kube

Do you have the 4th edition of Glass Notes? Pete wrote a whole section on glass melting. It's available for download.

Got 4th edition of Glass Notes but Pete's section in it was very short relative to the size of the topic (a much bigger topic now than it used to be because of modern environmental regulation) - the book that Pete was working on writing himself a few years ago sounds like it would be enormously valuable!

Originally Posted by Jordan Kube

You're up on a mountainside, so I'm guessing you're not going to really want a pot that holds more than 15-30 pounds. At lest that's all I'd want to carry at one time. Dave Bross has some decent clear recipes posted here. The point Pete is trying to make is you can talk about swimming all you want but at some point you're going to have to jump in the water.

I wrote a fairly long and careful reply but unfortunately Firefox glitched and lost it all (I've lost a few posts on here that way - the longer I spend writing them the more likely it seems that something glitches and looses them - does anyone have any suggestions on how to avoid that or how to get them back?).

I'll try to summarize:

Pete, Josh and Scott have been an enormous help by telling me that I need to aim to run my furnace at c. 1260 to 1280 °C to make Zn Ba SiO2. (There seems to be a lot of well-intentioned but misleading information out there from folk who only remelt glass rather than making it.)

Thanks for mentioning Dave Bross - been reading his posts and replying to some of them - craftweb only found 30 posts by him when I searched but I'm guessing from what you said and the depth of some of his posts that he must have posted a lot more that craftweb doesn't seem to be finding?

Found suppliers in Europe for refractory and materials -

https://www.lohnerziegelei.ch/

http://www.glassworksservices.co.uk/

https://www.ctmpotterssupplies.co.uk/

The FeCrAl electric striking / annealing / fusing oven is already built (using home-made ceramic insulation because it's all I had at the time) and running beautifully under computer control (gotta do some tests on temperature homogeneity but initial results are encouraging).

Got to work out how to heat the melting furnace now - options seem to be:

FrCrAl - I know that people have been successful in remelting but not making glass with FeCrAl furnaces but I may be able to overcome some of the limitations by very careful refractory design and computer control.

SiC - SiC heating elements can change in resistance by 10 x depending on age and temperature but I may be able to overcome this using careful electronic design and computer control.

MoSi2 - Very fragile so may not survive European postal system and my clumsiness. I think I may be able to overcome the need for large, expensive transformers for both MoSi2 and SiC by using modern power electronics.

SiC as a microwave susceptor - what I used when I was starting out with glass - used on a large scale to vitrify high level nuclear waste into inert glasses - has anyone in the art glass community had success with this?

All have advantages and disadvantages and I'm just learning about some of them.

I have to move up from tiny batches to larger batches as Pete recommended.

Emissions control is a work-in-progress - will take a while for parts to arrive...

Originally Posted by Jordan Kube

Believe it or not the glass making is the easiest part of this whole thing.

Uh...oh - what comes next?

Right - I haven't been able to re-type all of this message but gonna hit "Submit Reply" before it gets lost - again...

[Will Robertson]

Originally Posted by Pete VanderLaan

The utility bills are the hard part.

Electricity here is 29 Cents per kWh during the day and 21 Cents per kWh overnight - propane in tanks is is 4.45 to 6.67 USD per litre. 😔

[Will Robertson]

Originally Posted by Jordan Kube

Do you have the 4th edition of Glass Notes? Pete wrote a whole section on glass melting. It's available for download.

Yup - though I reckon that the book (the thread on here is archived so I can't reply to it) that Pete mentioned he was working on a few years back will be much better.

Originally Posted by Jordan Kube

You're up on a mountainside, so I'm guessing you're not going to really want a pot that holds more than 15-30 pounds.
At lest that's all I'd want to carry at one time.

Yup - our rule-of-thumb from armed forces was not to try to lift anything over 20kg single-handed.

Also I'm thinking a lot about moving from here to a more accepting culture - if I did that I'd have to re-build everything from scratch when I move - so trying to keep things small.

Originally Posted by Jordan Kube

Dave Bross has some decent clear recipes posted here.

Thank you very much!

I've found that the search function on Craftweb sometimes doesn't seem to work the way I expect it to (like when I searched for "oil" and didn't get any results 🙈 ) so I tried googling "craftweb Dave Bross" - I'm also reading through all his craftweb posts now (thought there are only 30 posts listed and I suspect from what you said that he must have posted much more than that)

https://www.google.com/search?q=craftweb+Dave+Bross

Originally Posted by Jordan Kube

The point Pete is trying to make is you can talk about swimming all you want but at some point you're going to have to jump in the water.

Thanks to Pete, Josh and Scott, I now know that for making Zn Ba SiO2 glass I need to run my furnace at 1260 to 1280 °C - that alone is an enormous help (the low temperatures quoted by remelters and the high temperatures quoted by boro makers had confused the wits out of me).

The computer controlled striking / annealing furnace is already built using home-made refractory materials and working very well.

http://www.glassworksservices.co.uk/ have been an enormous help in glass chemistry and supplying pure materials.

https://www.lohnerziegelei.ch/ are able to supply some high temperature refractory materials which they don't mention in their catalogue - you have to ask them about them.

Pete pointed out that small volumes of glass would be interfered with by oxygen from the air and the walls of the crucible partly dissolving.

I have to work out now how to get a large enough batch up to 1260 to 1280 °C - propane is easiest but expensive and difficult to get here - oil doesn't seem practical at smaller-than-industrial scales and may not be available 10 or 20 years into the future - that leaves me with FeCrAl, SiC and MoS2 heating elements and microwaves with a SiC susceptor.

FeCrAl - As far as I know, nobody here has been able to make glass using and FeCrAl furnace - only re-melt it - but I may be able to achieve this by very careful refractory and electronic design and computerized control (fairly capable computers are available for 50 to 60 USD now).

SiC - Resistance changes by a factor of up to 10 with temperature and age - but I reckon that I can maybe overcome this with carefully designed control electronics.

MoS2 - Widely used but it may be far too fragile to survive the European postal system and my clumsiness.

Originally Posted by Jordan Kube

Believe it or not the glass making is the easiest part of this whole thing.

SiC Microwave Furnace - I don't know anyone who's made glass this way (except low-melting-temperature glasses) but I think it may be possible.

Uh-oh - what comes next? I was expecting to just crawl into hibernation after pulling the first piece of Cu or Au ruby out of the striking furnace.

[Rich Samuel]

Originally Posted by Will Robertson

I wrote a fairly long and careful reply but unfortunately Firefox glitched and lost it all (I've lost a few posts on here that way - the longer I spend writing them the more likely it seems that something glitches and looses them - does anyone have any suggestions on how to avoid that or how to get them back?)

I'll take the easy one: Type your long posts into Word, or whatever you use for documents, and cut-and-paste it onto the board.