Nitric acid alternative for dissolving gold?

[Josh Bernbaum]

Originally Posted by Pete VanderLaan

It is certainly true that the gold rubies and purples are being made well in Boro with no lead.

So is the network somehow different in a boro melt that allows for the gold to disperse evenly without lead? And is lead problematic in a boro mix for some reason?

[Pete VanderLaan]

I don't .spend time on boro and its makers so I can't comment and they won't tell you the truth.
I do think that if you start in on making a variety of borosilicate glasses that you will run into either mismatch or thermal shock issues PDQ, or the melt will look like shit.

I don't know enough to subscribe to your theory of gold dispersement. I tend to think that color showing is as much based on valence as anything else. It certainly seems the case in soda limes as to what network stabilizer gets chosen. Ex: calcium vs strontium or zinc. They all yield differing results. That's the case for the modifiers as well but is limited to sodium, potassium and Lithium. That's a boatload of variety. Now consider lead and barium. Staring at the periodic table really is helpful ( but it hurts your head). Then of course you can go bonkers with titanium and phosphates.

[Will Robertson]

Originally Posted by Pete VanderLaan

Silicon will reduce indeed but will convert to Si02. It has no staying power, also a problem with sugar or SiC. Use Black tin.

Yes - definitely agree - I think some source of Tin - particularly Sn(II) from Black Tin Oxide SnO is critical - I call the colour "Copper Tin Ruby" or "Cu Sn Ruby" - I think I remember reading some research done with highly purified chemicals that showed that it was difficult or impossible to get a good copper ruby colour without some Tin being present.

[Pete VanderLaan]

I make specific base glasses for colloidal color work. High in potassium, no nitrates at all. That is a neutral glass and hard to fine out. Adding zinc and tin set the process in motion for stringy little molecules that are the darling of opalescent seekers. Gold needs lead. I think that pursuit of non leaded rubies using gold to be unlikely at best. It's feasible but not worth the effort. We always seem to want what we can't get.

Glassblowers are simply not dying from metal poisoning. Alcohol and Tobacco are the demons.

[Will Robertson]

Originally Posted by Pete VanderLaan

I make specific base glasses for colloidal color work. High in potassium, no nitrates at all. That is a neutral glass and hard to fine out.

Is that your Guadalupe Zinc Base 2013 recipe? (I wasn't sure whether to type the recipe here or whether you'd prefer to keep it confidential.)

I was planning to use your recipe or some of the expired patents (Schott, Corning and a fairly detailed European patent for a Zinc Barium Silicate glass by an Austrian glass maker) as the basis for making colloidal/striking colours.

I don't mind fining problems - contrary to accepted practice, I actually like bubbles in the glass because I feel that they add artistic interest.

I had a question about recipes using your VDL CS Fluorine Opal Base "Millenium White" - they say "Melt very lean throughout." - I wasn't sure what "lean" meant in that context?

Originally Posted by Pete VanderLaan

Adding zinc and tin set the process in motion for stringy little molecules that are the darling of opalescent seekers.

Thank you very much - that's interesting - I do a sort-of semi-opalescent-semi-clear partially iridescent silver colloid glass and this knowledge might be a big help for making it more reliably.

Originally Posted by Pete VanderLaan

Gold needs lead. I think that pursuit of non leaded rubies using gold to be unlikely at best. It's feasible but not worth the effort. We always seem to want what we can't get.

Thanks - I'll put any thoughts of non-lead gold rubies to one side until there's more time, more money and more research available (probably at least several years from now...).

Originally Posted by Pete VanderLaan

Glassblowers are simply not dying from metal poisoning. Alcohol and Tobacco are the demons.

Yes. Modern PPE has become very efficient and most heavy metals can easily be detected in urine samples so people can easily be screened for exposure. There are even very cheap and simple test strips available now which can detect any lead contamination in tiny concentrations. There are other things which seem vastly more likely to kill us sadly.

[Will Robertson]

Originally Posted by Pete VanderLaan

Torit filters on Donaldson units. Really expensive actually. The only thing that will give you clean air. Ask Bullseye.

Yup - I studied everything I could find about Bullseye's experiences - gained a lot of information from their disclosures.

I'll ask a friend who's a professional welder what systems he uses - he creates hazardous amounts of hexavalent chromium and other heavy metal fumes whenever he welds stainless steels - the measures for controlling these are strictly regulated but not prohibitively expensive in the welding industry - I train with him and he's a very good fighter - nothing wrong with his health at all!

[Pete VanderLaan]

Guadalupe Zinc Base 2013 recipe
***
Where did you get that? I can't recall publishing that anywhere except for my students at the time. John Croucher usually refers to any of my formulations under title VDL when he is looking at them but that's another matter..

Golds need lead as does moss green need lead from copper

[Will Robertson]

Originally Posted by Pete VanderLaan

Guadalupe Zinc Base 2013 recipe
***
Where did you get that? I can't recall publishing that anywhere except for my students at the time. John Croucher usually refers to any of my formulations under title VDL when he is looking at them but that's another matter..

I was hunting for patents, research papers and anything else I could find about coloured zinc barium silicate glasses when I found a scan of spreadsheets with glass recipes - I realized that whoever had written them had a very deep understanding of what they were doing so tracked you down.

Originally Posted by Pete VanderLaan

Golds need lead as does moss green need lead from copper

Is moss green a green where the lead glass matrix causes the Cu(II) ions to appear green instead of blue-green?

[Will Robertson]

Originally Posted by Pete VanderLaan

The trouble with tiny batches is many fold.

Another problem with tiny batches is that convection currents don't mix them in the same way as they do larger batches. The only way I've found to overcome this so-far is to stick in an alumina rod and stir them manually - which isn't ideal...

Originally Posted by Pete VanderLaan

The first I run into is the law of significant figures. If you are trying to get (Example), 1/10th f one percent red copper into 65 grams of your formulation, , 10 percent would be 6.5 grams. 1 percent would be .65 grams and 1/10th would be .065 grams. That's not a large number and the scales need to be better than what I own to get there and my scales are good.

Then, take your .065 grams of copper and try to mix it evenly in the original batch. Good luck.

I've got a chemical balance that can weigh down to 0.01 g (10 mg). The trick used by the pharmaceutical industry is to thoroughly mix a small amount of active ingredient with a larger amount of a carrier (e.g. for glass: anhydrous borax or sodium carbonate) - this makes measuring easier.

Originally Posted by Pete VanderLaan

Then, put it in a pot with a 4 inch surface area. I imagine 65 grams to be a bit more than two large spoons in volume, so the glass will pretty much sit on the floor of the pot. It will be exposed to the atmosphere of the kiln which I imagine to be wire element , so it's oxidizing which is the last thing reds need. If you accept the notion that a glass is largely affected by it's internal atmospheric conditions with the exception of the top 1/2 inch of the melt being affected by the kiln itself, you now have an irreconcilable problem. It's why I don't rely or results from small batches.

Yes - this is a significant problem. My largest crucible is 3 inch diameter and the others are smaller - on this tiny scale the exchange of oxygen between furnace atmosphere and melt is a much bigger problem than in commercial batches.

The only ways that I can think of handling this are:

Keep crucible covered with a lid as much as possible.

A slow flow of inert gas into the furnace to keep oxygen out.

Build oil fired furnace which can be pushed into reducing conditions without having to worry about wrecking oxide layer on FeCrAl wires.

Bigger batches (not possible at the moment).

Originally Posted by Pete VanderLaan

I don't use auric vials for my gold. I did have to use them in Shanghai. They are profoundly expensive and you get far better bang for your buck making your own gold chloride solutions and then adding them to silica. Croucher just dumps it in the batch but I have my methods. They are indeed outlined in the Lyngaard publication but I don't think they were part of the Schmidt document.

Think I've worked out how to get gold leaf into solution without involving HNO3 - I don't have any gold to try it with at the moment unfortunately.

Originally Posted by Pete VanderLaan

If you can't find black tin, Stannous chloride is an almost satisfactory substitute. Copper rublies perform far better in a high potash and zinc base. Sodium is really a junk material.

Thanks!

(I'm on the hunt for Stannous chloride for something else at the moment but it seems to be difficult to get over here unfortunately.)

Originally Posted by Pete VanderLaan

It is certainly true that the gold rubies and purples are being made well in Boro with no lead. The Asheville bunch is doing great bubble free stuff. It's all from raw batch but melted nearer to 2700F. As to lowering the melt temp on Boro, good luck. That would change the viscosity if nothing else and then we'd have two glass type groups bitching about mismatch. 33 is such a nice not round number.

Thanks - 2700°F is beyond what my FeCrAl furnaces can safely do - might build a better Silicon Carbide (SiC) microwave susceptor furnace and see if it can get up to this sort of temperature - guessing that for melting the exact temperature doesn't need to be carefully controlled in the way that it has to be for striking?

[Pete VanderLaan]

I don't know why the chromophore do what they do in the green. It's simply not a color I ever used in my work but it's beautiful. Much like a British Racing Green if you liked Jackie Stewart.

I use a zinc potassium base for my cad sel reds. I find it to be really difficult to get a good red without at least two percent zinc. I simply found the name interesting.
The VDL CS stands for VanderLaan/ Chuck Savoie. Millenium White was our base fluorine white in the Flying Color days. It had its issues.

2700F is a nasty temperature and everything lasts way less time up there. My Friend Scott says that getting anything in the UK is a major obstacle.

[Will Robertson]

Originally Posted by Pete VanderLaan

I use a zinc potassium base for my cad sel reds. I find it to be really difficult to get a good red without at least two percent zinc. I simply found the name interesting.
The VDL CS stands for VanderLaan/ Chuck Savoie. Millenium White was our base fluorine white in the Flying Color days. It had its issues.

👍 Cd seems to be effectively banned in Europe now so I may have to stick to other reds.

Originally Posted by Pete VanderLaan

2700F is a nasty temperature and everything lasts way less time up there.

I'll fight away with it and see where I can get. At the moment I can make cobalt blue borosilicate, copper blue borosilicate, leaf green borosilicate and a leaf green aventurine borosilicate (all from frit). Amber and colloidal borosilicates have been much more difficult though and I can't make them reliably yet.

Originally Posted by Pete VanderLaan

My Friend Scott says that getting anything in the UK is a major obstacle.

I can help him with that - battled with that for a long time - for glass making materials, colouring oxides and refractory materials:

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

and their sister company

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

for refractories:

http://swpuk.com/swp-refractories/

[Pete VanderLaan]

Scott is in N. Ireland and knows where to not be able to find stuff.

For your boro opaques, think zircon, lots of it. most of those guys are not melting scrap above 2380F and running through elements. They mostly use 90% alumina pots and run through them as well.

I have a lifetime supply of cadmium. Eveline brings selenium in her Easter bunny basket. What would be nice would be a lifetime supply of gold. My neighbor found 7lbs of it in his father's barn. No kidding.

[Will Robertson]

Originally Posted by Pete VanderLaan

Scott is in N. Ireland and knows where to not be able to find stuff.

Put him in touch! I've got some techniques for finding hard-to-find stuff.

Originally Posted by Pete VanderLaan

For your boro opaques, think zircon, lots of it.

Zirconium in glass is something that I haven't been able to find much about - though I know it's used in high temperature refractories. Does it have any uses apart from as an opacifying agent? (I'm speaking from a purely selfish perspective here - I'm much more interested in clear and opalescent glasses than opaque.)

Originally Posted by Pete VanderLaan

What would be nice would be a lifetime supply of gold.

I'm fairly confident that I can work out a way of dissolving gold on a small scale without a supply of HNO3 and HCl - the gold itself is more tricky.

[Josh Bernbaum]

Will, I'm curious what limitations you've found in melting the colors you've done in an electric melter. Have you tried copper rubies yet? I haven't myself (I still prefer the look of the toxic reds unfortunately..) but I was under the thinking that a reducing atmosphere would be important, even in addition to the reducing agent(s) in the batch. Pete has said that atmospheric conditions might only effect the top 1/2 inch of the melt but to me that sounds like every gather would probably get some of that top layer scooped up. Unless maybe the surface could be 'raked' back immediately before gathering which would be much harder to do in a tiny pot I imagine. You can't do fluorines of course, but maybe that's just fine with you. And depending on how hot you're able to get your wire melter, I envision potential issues with properly melting chrome-containing glasses or phosphates which I've so far found benefit from higher melt temps.

Also wondering what you do with the tiny amount of hot glass you are able to pull out of 3 inch pots.

[Pete VanderLaan]

The issue with the top 1/2 inch is based around the percentage of the melt that is in the top 1/2 inch. If the pot has any depth at all, it's not relevant. If it has no depth, it is relevant.

In my mind, tiny batches are not going to give quality results and I've already stated why. If you can weigh a chemical at six milligrams how are you going to get it in the frit ( not batch) evenly? Even then, now the top half inch comes into play in a 65 gram melt. I don't know anyone who expects meaningful results doing that. At the least, a furnace with neutral atmosphere would be a good idea.
It's probably better pursued elsewhere as this forum doesn't really deal in boro issues.

[Will Robertson]

Originally Posted by Pete VanderLaan

The issue with the top 1/2 inch is based around the percentage of the melt that is in the top 1/2 inch. If the pot has any depth at all, it's not relevant. If it has no depth, it is relevant.

In my mind, tiny batches are not going to give quality results and I've already stated why. If you can weigh a chemical at six milligrams how are you going to get it in the frit ( not batch) evenly? Even then, now the top half inch comes into play in a 65 gram melt. I don't know anyone who expects meaningful results doing that. At the least, a furnace with neutral atmosphere would be a good idea.
It's probably better pursued elsewhere as this forum doesn't really deal in boro issues.

That's a very important point. The cost of time consumed trying to interpret potentially misleading results from a small test melt might end up being much more than the cost of ingredients and fuel for a much larger test melt.

Thinking over what you said in detail, I can see that having that top 1/2 inch layer in an unknown redox state could make the results from small batches very misleading and trying to interpret them could result in a lot of wasted time.

I'm Scottish and perhaps my efforts to minimise costs by doing small test melts are a bit too Scottish...

I ordered some 50 ml alumina crucibles with lids a few weeks back - larger crucibles with lids seem hard to find so I might try just using a sheet of alumina as a lid so that I can upgrade to larger crucibles. I'll also try to purge the furnace with an unreactive atmosphere.

[Will Robertson]

Originally Posted by Josh Bernbaum

Also wondering what you do with the tiny amount of hot glass you are able to pull out of 3 inch pots.

Plan is to pour it out, cool and anneal into discs of mostly clear glass with some areas of colour. Another option would be to grind the glass to frit then fuse together again into discs like the above. These would then be given to friends to hang in their windows.

May also try to blow the glass into Christmas bobbles at a later stage.

All of that sounds fairly unambitious but had to learn everything from scratch and design and build the furnaces from scratch so kept me out of trouble.

Originally Posted by Josh Bernbaum

Will, I'm curious what limitations you've found in melting the colors you've done in an electric melter.

Built one furnace with FeCrAl heating elements that I use for striking and annealing - I can control the temperature of that very accurately (K and J type thermocouples) but it's limited to c. 1100 °C. Got another microwave furnace with silicon carbide (SiC) susceptor - that can go to high temperatures but no way of controlling the temperature accurately (as far as I can work out, optical pyrometers working at high temperatures get expensive).

Have been able to get the ionic colours starting from scrap soda lime and borosilicate but finding the colloidal colours more difficult.

Originally Posted by Josh Bernbaum

Have you tried copper rubies yet?

I've been able to get patches of haphazard copper tin ruby in borosilicate frit but I need to get a more reliable way of doing it.

Originally Posted by Josh Bernbaum

I haven't myself (I still prefer the look of the toxic reds unfortunately..)

Are those Cadmium Selenium (Cd Se) reds? (We're not allowed cadmium over here unfortunately...)

Originally Posted by Josh Bernbaum

but I was under the thinking that a reducing atmosphere would be important, even in addition to the reducing agent(s) in the batch.

A reducing atmosphere is important for Cu Sn ruby in pottery glazes where the ratio of surface area to volume is much higher than for glasses. I think it should be achievable in glasses using an inert rather than reducing atmosphere.

This guy's PhD thesis studies copper ruby reds manufactured in small batches (link to download the full PDF is at top-right):

http://kth.diva-portal.org/smash/rec...81&dswid=-9439

Reducing atmospheres tend to reduce the lifetime of FrCrAl heating elements so if they are necessary would probably be better done in a microwave or oil fired furnace.

Originally Posted by Josh Bernbaum

Pete has said that atmospheric conditions might only effect the top 1/2 inch of the melt but to me that sounds like every gather would probably get some of that top layer scooped up. Unless maybe the surface could be 'raked' back immediately before gathering which would be much harder to do in a tiny pot I imagine.

Yup - based on what Pete said I'm moving away from the idea of tiny batches. Some materials evaporating from the surface and traces of the crucible dissolving in the glass and altering the composition would also be a problem in tiny batches.

I'm becoming more and more doubtful about using cutlet - with cutlet I don't know the batch redox and I don't know what decolourizing chemicals may have been added to it during manufacture - or even whether chemicals which may inhibit colloid formation may have been added during manufacture.

This guy was able to make photochromic glasses in tiny batches but using a lower melting point glass (he based it on an aluminium calcium borate glass):

https://www.youtube.com/watch?v=mUcUy7SqdS0

Originally Posted by Josh Bernbaum

You can't do fluorines of course, but maybe that's just fine with you.

I'm guessing that fluorines are mainly opaque glasses? I'm fine without any opaque glasses.

Originally Posted by Josh Bernbaum

And depending on how hot you're able to get your wire melter, I envision potential issues with properly melting chrome-containing glasses or phosphates which I've so far found benefit from higher melt temps.

I've been able to get chrome leaf greens but I haven't tried any phosphates yet. It's not possible to buy a copy of Chemical Approach To Glass in Europe now so I'm working from Weyl and a heap of research papers and patents which makes progress fairly slow and difficult

[Pete VanderLaan]

you list yourself as being from multiple countries including the USA. It is indeed possible to buy, it's just expensive. It indeed is worth owning.

When you refer to pours with partial color and some clear, it's exactly what I'm talking about with inadequate mixing. It screams that the chemicals added didn't go into solution easily. That in turn implies that there's too much by calculation in some parts and too little in others.

Most of the colors you are achieving are solution based. They require no other circumstances to create a color. That's pretty straight forward and doesn't need sophistication. Sophistication is where the colloids start to walk on stage. Then again, there are way worse problems than colloids.

Copper blue in cullet is easy. copper ruby in cullet isn't.

[Will Robertson]

Originally Posted by Pete VanderLaan

you list yourself as being from multiple countries including the USA. It is indeed possible to buy, it's just expensive. It indeed is worth owning.

I'm from Scotland and living on a mountainside on the Northern flank of the Swiss Alps at the moment - hoping to travel over to US and Canada more once COVID-19 travel restrictions ease. Unfortunately the folk on Amazon selling Volf won't post a copy outside the USA and the nearest library copy seems to be several hundred km away in Germany.

Originally Posted by Pete VanderLaan

When you refer to pours with partial color and some clear, it's exactly what I'm talking about with inadequate mixing. It screams that the chemicals added didn't go into solution easily. That in turn implies that there's too much by calculation in some parts and too little in others.

Yup - this is exactly the effect I'm looking for. I don't like large areas of uniformly coloured glass - I see glass as a clear 3 dimensional space within which colours can exist - I've also got very unconventional views on bubbles - I regard large bubbles as being mirrors which reflect an internal perspective on this space to the observer.

I'm also working on introducing changes in refractive index within the glass to give even more non-uniformity.

To me, there's an enormous energy in home-made colours that is not present in more controllable media. They provide a direct link from the world of human observation to the world of quantum mechanics that no other media can supply. They express the ligand field in which the ions exist and the nonlinear optics of nanoparticle colloids. They provide the ability for colours to exist independent of surfaces which no other medium can supply.

Originally Posted by Pete VanderLaan

Most of the colors you are achieving are solution based. They require no other circumstances to create a color. That's pretty straight forward and doesn't need sophistication. Sophistication is where the colloids start to walk on stage. Then again, there are way worse problems than colloids.

Copper blue in cullet is easy. copper ruby in cullet isn't.

Yes - the solution/ionic colours are relatively easy - the colloid colours much more difficult. Modern XRF spectrometers can measure everything heavier than beryllium but without an XRF spectrometer the task of working out the chemistry and batch redox of cutlet seems very difficult.

What are the worse problems than colloids?

[Greg Vriethoff]

Originally Posted by Pete VanderLaan

I dissolved my wedding ring for my first batch.

Just out of curiosity (I haven't worked with aqua regia, etc.), how much do gold alloys affect the results? It's was most likely 14k (maybe 18). I'm assuming the purity of the gold needs to be taken into consideration.

[Pete VanderLaan]

The ring was 24 carat. I have never attempted to use any alloy. I can say that in making silver nitrate, I have frequently used American coinage as well as fine silver. It makes a difference in the colors. Copper added to silver based colors tend towrds striking peaches but in unreliable ways.

In pots, if the pot is not essentially new, the slightest amount of silver presence in a gold ruby will tend to develop a color more like brand new motor oil. Not what I want. I work the gold for purples more than anything else although the wine reds are beautiful. I don't do it much anymore although Mary Beth and Eveline are making noise about wanting ruby tubing.

[Greg Vriethoff]

Thank you. Just wanted to clarify. 24k gold jewelry is unusual, but not unheard of.

Silver for coinage can be all over the map. I have a bunch of roosevelt and mercury dimes that have no value to collectors, so I will be melting them down to make jewelry. I also have ten 1oz fine silver coins from the late eighties that I may use to make .925

[Will Robertson]

Originally Posted by Pete VanderLaan

The ring was 24 carat. I have never attempted to use any alloy.

Would gold leaf be suitable? (I'd read that gold leaf was c. 91.7% pure (22-karat) so I wasn't sure.)

I've been thinking more about how to help people with no access to HNO3 and HCl and worked out 3 methods of making gold chloride without HNO3 and HCl - I don't have any gold but initial tests with Cu seem encouraging and hoping to maybe get a small amount of gold within the coming months.

Originally Posted by Pete VanderLaan

I can say that in making silver nitrate, I have frequently used American coinage as well as fine silver. It makes a difference in the colors. Copper added to silver based colors tend towards striking peaches but in unreliable ways.

Thank you very much. We don't have much silver coinage in Europe unfortunately (apart from a silver commemorative coin that I was given to mark an anniversary in the fire service).

Originally Posted by Pete VanderLaan

In pots, if the pot is not essentially new, the slightest amount of silver presence in a gold ruby will tend to develop a color more like brand new motor oil. Not what I want. I work the gold for purples more than anything else although the wine reds are beautiful. I don't do it much anymore although Mary Beth and Eveline are making noise about wanting ruby tubing.

Thank you very much. That's probably saved me a fairly substantial headache and a lot of confusion down the line from now.

I was thinking more about what you said re. supply of gold. I'm enormously grateful for everything you've done to help me and I'd be happy to make contact with some galleries and shops in Zürich and talk about your work with them (I speak fairly fluent Swiss German and Zürich is about 2 hours by train from my mountainside). Your work is highly sophisticated and has enormous energy and beauty - it may be that the right galleries and shops in Zürich, Zug or Luzern could achieve a very good price for it (I'm just a forestry worker but there are others in Switzerland with vastly higher disposable income).

[Kenny Pieper]

Will,
I think that gold leaf will certainly work but is very expensive for the weight. Most people that I know making gold colors buy 24KY casting grains. Any jewelry supply store will have it.

[Greg Vriethoff]

I haven't found a better local source, so my go-to is Rio Grande. Spot price for gold is 1,901USD (geeze). I don't know if you'll have any issues shipping to the EU.

https://www.riogrande.com/product/24...g-grain/608700