Reduction Finishes
 

I've been interested in the metal components of glass formulations for quite some time. The glasses that reduce to give us such nice metallic finishes are of particular interest to me so I've looked into it a bit when the opportunity has allowed. Encasing will immobilize any reduced metal but a metallic surface exposes the reduced metal to wear. Below is an example of an exposed surface.

These are a few images of Rubino, aka Gold Ruby or Ruby Gold - all three have the same catalog number. These are paddles of the glass formed and reduced on the ends of rods. You can see that there are some color differences between the batches and there is a nice metallic sheen on the reduced ends.


These were taken with a scanning electron microscope (SEM) operating in backscatter mode. This means that areas of higher atomic number will appear to be brighter than lower atomic number areas. The first image is a reduced surface at an original magnification of 500X. The scale bar in the corner is 20 microns.


The second SEM image is the same glass as seen at 10,000 X, the scale bar is 1 micron. Each bright spot is a tiny bit of reduced metal on/in the surface of the glass - they're around 250 nm in diameter. For comparison, Staphylococcus bacteria on your skin are about 4 times bigger.



This is the X-ray spectrum taken from the area of the little square box in the first SEM image. The big peak marked Pb represents lead. There may well be some gold chloride in the glass for color, but most of the metal on the reduced surface appears to be lead.


It is a minute amount of lead, fair enough, but in light of the recent issues with the CPSC and lead content in products I'm not sure you would want to discount it totally. It is a surface coating, even if it's pretty thin (about 1 micron, more or less). I don't see it as a major health hazard but at the same time it pays to be informed about materials that you use. This is why I keep telling people to be sure that the name of a glass truly indicates the content or it it's a description of the color that it turns. Silver (*.*) and gold (*.*) may or may not be real elemental silver and real elemental gold.

Robert

Thank you Robert. It would be interesting to see just how much lead is in the glass itself. I doubt the lead contained in the matrix posses a health risk from handling... but working it and reducing these glasses may be more dangerous than I had realized myself. I personally would not have guessed lead was the material on the surface of reduced rubino. I was under the impression that gold was the main metal content for this color.

I'll add other glasses to this thread as I have time to look at them if there is interest.

I suspect that the lead based flux is necessary to get this glass to behave properly. It's my impression that traditionally gold ruby glasses have started out with a 'lead crystal' base, though in this use 'crystal' is a misnomer. The bulk glass probably has no more lead in it than your average fine crystal glassware, so I wouldn't worry about it from that point of view. The reduced surface may be another issue all together for some folks.

R

Very interesting post! I'm envious of the equipment and your access to it. I'd love to see more, if you're inclined to do further testing.

Linda

Ditto what Linda said,
I'd like to see more as well as you get to study the different glasses.

Robert, I am curious about the Bullseye lustres and would send some samples for testing.

Robert, thanks so much for posting this. You know of my interest in glass content, and with the CPSC it makes it necessary that we be even more aware of what is likely exposed on the surfact of our glass. Thanks again for all the time you have put into this.

And yes, we want MORE!

This is very interesting. i would like to see the same study done on different glass rods.


How and where did you get an x-ray spectrum test of the glass? Just curious.

I run electron microscopes for a living. I can occasionally get a little time to look at samples that are of interest to me if I buy time on the system.

Robert

very coooool. So...a bit off subject, what's the wierdest thing you've looked at under that microscope?

Weird is, as I have discovered, very much in the eye of the beholder. I'm primarily a biologist so I see all sorts of strange (and often fascinating) stuff. Failure analysis of materials gets pretty interesting, too. I'd have a hard time picking out the all-time strange sample.

robert

Robert,
Thanks so much for your work on this. It is nice to have the proof so that people can make informed decisions.

Ohhh yes lead is much more prevalent that you think and I have wondered about this for some time now - thanks for being so thorough in your investigation RSimmons. We need to know everything we can ~ I wonder even more so about the China made glasses i.e. messy.... it makes sense they may have more than we are used to having, and since they are so shiny and vibrant, there must be a reason ! Keep us posted please & Thanks again R Simmons ...you rock !

Dark Turquoise
 

Just to show it's not all about lead content I ran up a sample of Dark Turquoise. Here it is strongly reduced to show the coppery red color that develops. There is a little bit of a silvery grey surface on less reduced areas. Some people like this color and develop it by heating the glass in a high fuel/low oxygen (reducing) flame.


Low magnification SEM of the edge of a strongly reduced area.


Higher magnification image of a strongly reduced area of the glass. Metals tend to form particle clusters on the surface.



X-ray spectrum of a strongly reduced area shows a concentration of copper on the surface. The potassium and calcium are probably flux components and there is a small amount of zinc present as well.


Robert

That's interesting. Definatly not as worrisome as lead.
If you are inclined and get an opportunity maybe try one of the gold looking reduction glasses like kuglar 218. I wonder what that is? Can't be gold. If you have are interested in testing anything that you don't have on hand, I am sure one of us who does would be more than willing to send you a chunk.

Thank you for keeping us posted on your findings.

=D>Well this is just so interesting!!!!!!Now Im dyeing to see more.

Karen
Volkano Exotik

I got some K215 last week and will have a look when I get the chance.

Thanks,
Robert

Robert, thanks again. You are so wonderful for providing us with this information.

This is very, very interesting.
Thank you for your time.
We are all watching!

How about some Boro colors, like Amber purple, and silver beach? they're not reduction colors but it would be interesting to see which metals cause the haze that we burn off.

I may have some of those somewhere in the studio. Not much boro around, but there is some here and there.

R

I took a look at some K215 Gold Brown that someone gave me. As before, I made a paddle on the end of the rod and reduced it to a metallic sheen.

There are similarities to structures that we've seen before with the formation of small 'beads' that are similar in structure to the lead that we've seen in other glass.


The spectrum from the bright 'beaded' area shows a high lead signal as well as the presence of silver


The spectrum from the darker areas of the image shows lower levels of both metals.


It appears that the bright metallic surface of this glass when it is reduced is due to the condensation of both lead and silver in a thin layer. Lead is a commonly used flux component in many glasses and K215 is NOT listed as a lead free color.

R

Thanks again, Robert. Have you tested any of the "silver" colors? Do you expect those will have the lead content?

I think probably what we are missing on some of these glasses is whether they are lead free or not. I know BE lists whether a glass contains lead, but I haven't seen this for other glasses.

I've got a few of the 'silver colors' on my list of things to look at as time and $$ allow. It doesn't look like there is a lot of information about the actual components of the various glasses out there. BE has a good list and Kugler has a separate "Lead Free Color' section as, I believe, does Satake. I expect that in the future more of the manufacturers are going to want to disclose lead content even if they keep their other color components a close secret. More on the silver colors soon, I hope.

R

Thanks again.

I think I will keep the reduction finishes for ormaments and vases and such that won't be worn next to the skin or handled very much.

Thanks for this, Robert. I found it fascinating and informative! And I won't be sucking on my beads anytime soon! :)

Very Interesting!!
Thanks.
Paula

Thank you for doing this! I hope you can test more glasses. This is very interesting.

Or just encase them.:idea:
Thank you for the info Robert.