Nitric acid alternative for dissolving gold?

[Josh Bernbaum]

I was ordering some more sodium nitrate online today and ran across this page on their site claiming that this product can replace the Nitric Acid in an aqua regia process (still need HCl though I think). Any thoughts?:

https://www.ishor.com/mx3-dissolving-agent

[Pete VanderLaan]

I can certainly see that the sodium nitrate would make an acid which would be attached to a base. HnO3 would be the regular acid but I assume this would make up some sort of NO3 that would have inclusive sodium, not something I'm sure if I would want.

It is a pain to get the nitric delivered these days. Ultimately, I got it from Graingers.

But you go first...

[Josh Bernbaum]

When it was delivered, I had to sign some form for the Nitric I ordered a while back. No doubt I'm on some sort of list now that I've had that and CdS and K dichromate shipped to my house over the years. But since our EPA have been instructed to promote extra pollution these days, maybe I don't need to worry. That mostly full bottle of Nitric does make me nervous though..

[Bradley Howes]

There's always sodium cyanide...

[Will Robertson]

Originally Posted by Josh Bernbaum

When it was delivered, I had to sign some form for the Nitric I ordered a while back. No doubt I'm on some sort of list now that I've had that and CdS and K dichromate shipped to my house over the years. But since our EPA have been instructed to promote extra pollution these days, maybe I don't need to worry. That mostly full bottle of Nitric does make me nervous though..

I was thinking along similar lines to you. I can order concentrated nitric acid in a minimum batch of several 10s of kilos and having that sort of quantity around would make me uncomfortable as well so I was looking for a better way.

A mixture of concentrated H2SO4, KNO3 and NaCl would give fumes of HCl, Cl2 and nitrogen oxides - these may be able to react with gold from the gaseous phase in the same way as an H2SO4, HNO3, HCl mixture - the process would be inefficient in its use of these reagents but efficient in its use of gold so I think it might work in small quantities.

Another approach would be to use an electrochemical process.

Re.

Originally Posted by Bradley Howes

There's always sodium cyanide...

I think that might work. Cyanide is fairly toxic but it would be used in tiny quantities and my guess is that it would rapidly react with other components of the melt, decompose or boil off from the melt. A lot of plants manufacture cyanide-containing molecules to try to prevent animals like us eating them so it is a naturally occurring molecule.

[Pete VanderLaan]

This somehow reminds me of a line from "A Confederate General from Big Sur", in which the protagonist is trying to get frogs out of a pond and releases small alligators.

Silence:

And Lee Mellon says "That takes care of the frogs. "

Jesse replies "Yeah nothing in there now but alligators. "

Great book.

You don't want cyanide..

[Will Robertson]

Is the problem with cyanide its toxicity or the effect that it has on the glass making process? My guess is that it must act as a fairly strong reducing agent in glass batches and maybe have a tendency to boil off too early in the process but beyond that I've no idea.

Reckon best to abandon cyanide altogether and stick with the HCl HNO3 route?

Cyanide is present in many fruits and gets distilled over when we make schnapps - it's also present in significant amounts in several traditional European plant-based delicacies - including those made for children - so there's a fair amount of research in Europe about how much cyanide humans can be exposed to before it becomes harmful. The great thing about cyanide is that it's a naturally occurring molecule and one we've been exposed to most of our evolution so our bodies have ways of dealing with small amounts of it and it doesn't bio-accumulate in our bodies - it has high acute toxicity but low chronic toxicity.

[Greg Vriethoff]

This is beginning to remind me of the website from about ten years ago telling everyone to not worry about formaldehyde as an industrial pollutant. Turns out it was the Koch brothers. There was increasing concern in communities near plywood manufacturers; Koch Industries has many such facilities.

Tag line was: "Formaldehyde. It's just a molecule."

[Will Robertson]

I think I read once that gold colloids were thought to give a much stronger colour in Pb-SiO2 based matrices than in other glass matrices - with increasingly strict restrictions on the use of lead in Europe perhaps the problem with gold colloid colours now is the lead in the glass matrix rather than the ligand used to dissolve the gold.

What are folks thoughts on this? Can gold colloids give good colours in lead-free glasses?

[Josh Bernbaum]

Originally Posted by Will Robertson

What are folks thoughts on this? Can gold colloids give good colours in lead-free glasses?

Not in my couple tries I've done without. John Croucher and Dave Bross both told me they thought it might be possible without Pb but it sure is much more difficult and sounds like more gold would be needed. John's suggestion was extra barium, but not over 5%, and extra gold (which I tried). Dave's suggestion was pretty much as much strontium as you can fit in there (I've got a lot of strontium in my phosphates already but there's room to try more). There's one page in Weyl that mentions gold colors without lead, but if I remember correctly it sounded inconclusive as far as if it's truly possible to do or not.

[Will Robertson]

Originally Posted by Josh Bernbaum

Not in my couple tries I've done without.

I can post a scan of the page from Weyl if that would be any help?

[Pete VanderLaan]

Gold without lead will likely be a weak tea. Barium would be the metal of choice to substitute but I would again expect, weak tea.
It seems to me that the Thuringen recipes had one listing for it but it's not like you're pouring tons of lead into the mix. People certainly don't seem to be getting kept up all night by using the bulk of German or Kiwi/ American color rods all of which contain at least 24% lead.

I've been making my own color forever and I only use lead in the ruby and black glasses. Given the price of gold, I'll use lead.

I don't view strontium as being a cure all in glass formulation. It is clearly helpful getting phosphates away from creating Apatite stones but I don't see where the effectiveness in gold recipes would be.

John is fond of 24% lead rod. He does sell rod by the kilo after all.

[Josh Bernbaum]

Originally Posted by Pete VanderLaan

People certainly don't seem to be getting kept up all night by using the bulk of German or Kiwi/ American color rods all of which contain at least 24% lead.

But the lead is in solution at that point, right? Maybe not the arsenic as we have discussed and how it can continue to volatize. I imagine people using bars that contain lead probably would be more concerned, if they were mixing the actual batch and being exposed to the fumes coming off the pot during the initial melt. I certainly am. I have 300 lbs. of bisilicate just sitting around that I don't plan to use until either I get senile or when my kid is out of the house next door to the shop here (whichever comes first) and therefore maybe less nervous about this.

[Will Robertson]

Originally Posted by Pete VanderLaan

Gold without lead will likely be a weak tea. Barium would be the metal of choice to substitute but I would again expect, weak tea.

Thanks - in that case I'll abandon leadless gold ruby except as a curiosity.

Originally Posted by Pete VanderLaan

Thuringen recipes.

What are the Thuringen recipes? I only know Gillinder, Weyl, your recipes and a clutch of research papers and patents. I can read German if that's any help.

(I tried Googling "Thuringen recipes glass" but got "Thüringer Rostbratwurst" and "Liver Sausage Bread" - both known human carcinogens but allowed by EU regulators... )

Originally Posted by Pete VanderLaan

I've been making my own color forever and I only use lead in the ruby and black glasses. Given the price of gold, I'll use lead.

What are your reasons for using gold ruby instead of copper tin ruby?

Originally Posted by Pete VanderLaan

People certainly don't seem to be getting kept up all night by using the bulk of German or Kiwi/ American color rods all of which contain at least 24% lead.

My understanding is that lead coloured glass was outlawed in Germany a few years ago (I think by EU REACH regulations). Gaffer Glass's MSDS declarations show it still in use there in some recipies - long live the Kiwis! http://www.gafferglass.com/informati...s-information/

(As a side-note on environmental regulation - Wikipedia comments "Inco alone accounts for 20% of all of the arsenic emitted in North America, 13% of the lead and 30% of the nickel." - I think their Superstack in its heyday might have belched out more lead in an hour as the entire U.S. coloured glass industry will in my lifetime...)

Originally Posted by Pete VanderLaan

John is fond of 24% lead rod. He does sell rod by the kilo after all.

[Will Robertson]

Originally Posted by Josh Bernbaum

But the lead is in solution at that point, right? Maybe not the arsenic as we have discussed and how it can continue to volatize. I imagine people using bars that contain lead probably would be more concerned, if they were mixing the actual batch and being exposed to the fumes coming off the pot during the initial melt. I certainly am. I have 300 lbs. of bisilicate just sitting around that I don't plan to use until either I get senile or when my kid is out of the house next door to the shop here (whichever comes first) and therefore maybe less nervous about this.

I'm gonna stick myself out on a limb here... Any time you go to a swimming pool or anywhere that food is prepared you'll see pristine, gleaming stainless steel surfaces - the steel stays like that instead of going rusty because of large amounts of chrome in high quality corrosion resistant steels (Chromstahl in German) - any time this is welded to build kitchen or swimming pool equipment, very dangerous quantities of hexavalent chromium fumes are generated. Garages and welding shops have portable or fixed welding fume extractors with powerful fans and electrostatic precipitators that clean the fumes and discharge purified air.

The free cutting machine steels used for precision machining don't contain significant amounts of chrome but many do contain significant amounts of lead which would also be released when they're welded.

My guess would be that it would be fairly inexpensive to get a used welding fume extractor or electrostatic precipitator from a garage or welding shop and pass the fumes from your furnace through it after they come out of the heat exchanger but before they go to the stack. (An extra heat exchanger might be needed to make sure the fumes are cool enough.) An extra extractor like this could also be used above the opening of the furnace to catch any emissions escaping into the room instead of up the stack.

The manufacturers of the welding fume extractors should provide technical data sheets and compliance documents outlining how effective they are at cleaning heavy metal fumes.

For PPE, 3M make filters especially designed to protect the user from metal fumes which can be used with their reusable respirators - or - for extra comfort and expense - powered air systems.

[Pete VanderLaan]

I don't believe that either Kugler or Richenbach has been limited by the EU on lead additions to rod formula. If that was true, there would be no enamels or gold variants. If the belief is that lead is going to poison your kids , then don't do it but I'm unaware of substitutes that will give similar results. My two grew up and seem just fine at thirty. At 71, I'm slipping.

I make more copper ruby than I do gold tone reds but I vastly prefer the gold for a depth that the copper doesn't have. Copper, passing through the thermal transitions is a bunch of different colors. I don't see that with golds. I don't make much glass these days.

Making copper ruby with cullet is like tying both hands behind your back. True of gold too. At least, that's my experience.

The Thuringen recipes by Wilhelm Schmidt were translated from the German by Finn Lyngaard back around 1995. The original German text can be found in the Rakow but they don't lend it. Finn has been dead now over fifteen years and the book is long out of print. It does have translation errors. Copies can be found by the persistent.

A book worth buying while it can still be found ( expensive) is Volf "A chemical approach to glass." That will never be reprinted.

Will, if you're looking for basic Boro recipes, go to the 1915 patent from Corning. It hasn't hardly changed at all. Still 81% silica.

[Will Robertson]

Originally Posted by Pete VanderLaan

I don't believe that either Kugler or Richenbach has been limited by the EU on lead additions to rod formula. If that was true, there would be no enamels or gold variants. If the belief is that lead is going to poison your kids , then don't do it but I'm unaware of substitutes that will give similar results. My two grew up and seem just fine at thirty. At 71, I'm slipping.

I'll need to do a bit more digging on this to reply properly...

Glassworks Services http://www.glassworksservices.co.uk/ in the UK now nolonger supply materials for making lead-based glasses - http://www.glassworksservices.co.uk/rawmaterials.html and http://www.glassworksservices.co.uk/...erialstwo.html - but their sister company https://www.ctmpotterssupplies.co.uk does still stock one lead-based glaze.

Originally Posted by Pete VanderLaan

I make more copper ruby than I do gold tone reds but I vastly prefer the gold for a depth that the copper doesn't have. Copper, passing through the thermal transitions is a bunch of different colors. I don't see that with golds. I don't make much glass these days.

Thank you very much - in that case I'll bear in mind maybe making tiny pieces of lead gold ruby for very close friends.

Originally Posted by Pete VanderLaan

Making copper ruby with cullet is like tying both hands behind your back. True of gold too. At least, that's my experience.

Thank you very much - that's an enormous help - I've been ripping my hair out trying to do copper ruby with borosilicate and soda lime cutlet for a while now - I can only do it with fairly haphazard results - knowing the experience you've had I'll put it to one side and focus on making colloidal colours only from raw materials.

Originally Posted by Pete VanderLaan

The Thuringen recipes by Wilhelm Schmidt were translated from the German by Finn Lyngaard back around 1995. The original German text can be found in the Rakow but they don't lend it. Finn has been dead now over fifteen years and the book is long out of print. It does have translation errors. Copies can be found by the persistent.

If I could get a scan of the German original and the translation I could correct the translation errors if that would be of any help?

Originally Posted by Pete VanderLaan

A book worth buying while it can still be found ( expensive) is Volf "A chemical approach to glass." That will never be reprinted.

Thank you - I've been trying to get a copy of this for a while but I haven't been able to find a copy that I can afford. The high price and scant availability of books on coloured glass making is a major headache and an enormous obstacle for people in my generation trying to learn.

Originally Posted by Pete VanderLaan

Will, if you're looking for basic Boro recipes, go to the 1915 patent from Corning. It hasn't hardly changed at all. Still 81% silica.

Thank you very much. That's US Patent 1,304,623?

Are there many coloured boro recipes out there?

[Pete VanderLaan]

no colored boro recipes. The makers are secretive and mendacious.

Volf is expensive. I have one of 20 known hard bound copies. It's not very well bound and the paper is cheap. It will be unlikely to get it for less than $200. Then, it will really go up. Originals from 1981 go at about 2K.

I hate tiny batches. I never make a batch less than 20 lbs. The surface area in the pot is actually quite important. The smaller the batch, the greater the surface area. I dissolved my wedding ring for my first batch. Even now, I want 3000 grams of gold sands available for a batch. The recipe for gold sands is in the Thuringen book just to drive you crazier.

The mistakes in Thuringen presume you can read an entire formula and see what is wrong. It is not for the inexperienced.

About copper reds, think about getting all of the oxygen out of the batch, as much as possible. Most cullets are oxidized. At the least they need to be melted once and fritted to drive the O2 off. Even then, more weak tea. Use stannous oxide as a reducer, accept no substitutes. It's black, not white.

[Jordan Kube]

I've never seen an actual boro recipe posted. I made one and sold it to a boro color maker recently. Something that relates to above is he's making gold rubies with it. There isn't any lead in the boroslicate glass. The different chemistry will produce some interesting colors and effects not seen in soft glass. My advice for doing colored boro is start with the same colorants and ratios as soft glass and experiment. Pound the shit out of the batch in a ball mill. The biggest challenge with melting borosilicate glasses are the temperatures needed to achive good results and your consumables are consumed at a faster rate.

[Will Robertson]

Re. the smiley on here with dark glasses - are they Didymium glasses?

Originally Posted by Jordan Kube

I've never seen an actual boro recipe posted. I made one and sold it to a boro color maker recently. Something that relates to above is he's making gold rubies with it.

That's very interesting. I have been able to get patches of copper tin ruby from boro frit (source: broken preserving jars) but not reliably and not in any quantity yet.

I do ionic colours from boro frit but have found colloidal colours much more difficult. (I don't know if that's an accepted thing - roughly categorizing colours as ionic or colloidal/striking?)

Originally Posted by Jordan Kube

The biggest challenge with melting borosilicate glasses are the temperatures needed to achive good results and your consumables are consumed at a faster rate.

This is a big problem for me as well. Running my home-made furnace hot enough to melt commercial boro is expensive and uncomfortable. Was thinking about having a go at making a lower melting point boro from raw ingredients to see what that can give.

Originally Posted by Jordan Kube

and your consumables are consumed at a faster rate.

Are alumina crucibles OK for melting boro? My first experiments with boro frit were so gloopy that I'm still working out how to get them out of the crucibles 🙈

Originally Posted by Jordan Kube

The different chemistry will produce some interesting colors and effects not seen in soft glass. My advice for doing colored boro is start with the same colorants and ratios as soft glass and experiment.

Yup - it seems very interesting. One thing I was unsure about was how to work out the striking temperature and time for colloidal colours in boro - my guess was that it would be hotter than for soft glass but that was guesswork.

Originally Posted by Jordan Kube

Pound the shit out of the batch in a ball mill.

Thank you very much - I'd been wondering about that - I was planning to build a ball mill but I wasn't sure if it had to be a minimum size to work effectively for glass. I work in tiny batches of a few hundred grams total (!) but I noticed alumina ceramic media for ball mills from this company ranging in size from 13 to 40 mm diameter and I wasn't sure what size would be best for glass:

https://www.inoxia.co.uk/products/ball-mill

(I don't mind leaving the ball mill running for days at a time.)

[Will Robertson]

Originally Posted by Pete VanderLaan

no colored boro recipes. The makers are secretive and mendacious.

Surely not! Boro makers? Secretive? Mendacious?

Was able to find this 1949 US patent though:

"and likewise our invention may be used for making copper ruby glass having a borosilicate base"

https://patents.google.com/patent/US2233343A/en

Originally Posted by Pete VanderLaan

Volf is expensive. I have one of 20 known hard bound copies. It's not very well bound and the paper is cheap. It will be unlikely to get it for less than $200. Then, it will really go up. Originals from 1981 go at about 2K.

With your encouragement I'll intensify my fight to try and get a copy.

Originally Posted by Pete VanderLaan

I hate tiny batches. I never make a batch less than 20 lbs. The surface area in the pot is actually quite important. The smaller the batch, the greater the surface area.

I can only work in batches of a few hundred grams max. unfortunately. Ordered some little alumina crucibles with lids to try to reduce interaction between glass and furnace atmosphere. Might try to fill the whole furnace with an inert atmosphere but cautious about producing a reducing atmosphere in the furnace which may damage the FeCrAl heating elements.

Originally Posted by Pete VanderLaan

I dissolved my wedding ring for my first batch. Even now, I want 3000 grams of gold sands available for a batch.

That's an amazing story. Your commitment to your art and the depth of beauty in your work are phenomenal and deeply humbling.

Originally Posted by Pete VanderLaan

The recipe for gold sands is in the Thuringen book just to drive you crazier.

The mistakes in Thuringen presume you can read an entire formula and see what is wrong. It is not for the inexperienced.

I'm guessing that your gold sands recipe is a lot better than the Thuringen one?:

To make the gold sands: Take one of the little bottles of gold solution. I believe each bottle contains about 5gms gold chloride. Mix 1 cup (.24L) hydrochloric acid...

Roughly what date were the Thuringen recipes originally written?

Originally Posted by Pete VanderLaan

About copper reds, think about getting all of the oxygen out of the batch, as much as possible. Most cullets are oxidized. At the least they need to be melted once and fritted to drive the O2 off. Even then, more weak tea. Use stannous oxide as a reducer, accept no substitutes. It's black, not white.

👍 Thank you very much! I'd strongly suspected that the redox of the frit was a problem. Been trying to push the radox of the frit using sugar and charcoal as reducing agents along with black Tin(II) Oxide - based on what Jordan said it sounds like I haven't been grinding the frit nearly finely enough though.

A pottery expert also suggested using silicon (in the form of the element not a compound) as a reducing agent in Cu Sn ruby.

[Will Robertson]

Originally Posted by Pete VanderLaan

no colored boro recipes. The makers are secretive and mendacious.

Also got my paws on these two German patents filed by Schott in 2004 then allowed to expire which seem to give detailed recipes for a borosilicate Cu Sn ruby (this time without involving CN):

https://patents.google.com/patent/DE102004001729A1/en

https://patents.google.com/patent/DE102004001729B4/en

Perhaps we should work naming new colours for boro makers? Mendacious Green, Surreptitious Blue, Machiavellian Purple, etc...

[Pete VanderLaan]

Black tin is what you want.

The trouble with tiny batches is many fold. 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.

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.

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.

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.

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.

[Pete VanderLaan]

Originally Posted by Will Robertson

. Garages and welding shops have portable or fixed welding fume extractors with powerful fans and electrostatic precipitators that clean the fumes and discharge purified air.



My guess would be that it would be fairly inexpensive to get a used welding fume extractor or electrostatic precipitator from a garage or welding shop and pass the fumes from your furnace through it after they come out of the heat exchanger but before they go to the stack.

.

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

[Pete VanderLaan]

[quote=
A pottery expert also suggested using silicon (in the form of the element not a compound) as a reducing agent in Cu Sn ruby.[/QUOTE]
*********
Silicon will reduce indeed but will convert to Si02. It has no staying power, also a problem with sugar or SiC. Use Black tin.