No more BS about Pb

A bit of an "aside." I've had the unpleasant experience of listening to several heated discussions on Facebook about lead safety. I've had multiple intelligent friends speak to me about concerns about their glasswork and non-glass friends worried about my health and safety.

I am impressionable when it comes to medical matters, so a heated discussion on a wonderful Facebook group for glass artists left me a bit paranoid. At the time I spent a bit of money to build a better ventilation system, researched lead safety extensively, and discussed it with everyone I knew. I had been made to believe, however briefly, that my love of glass was killing all of my loved ones who set foot in my house.

Not happening. Today's post is going to cover some lead safety "Fact or Crap" items.

The big Fact: The significant threat is ingestion, not inhalation.

Think of lead much like water. Is ice contributing to the humidity of your air (are you inhaling it?) Yes, technically. A tiny portion of the ice can sublimate straight into water vapor. But it's so little it's insignificant. Is liquid water sitting in a glass adding to your humidity? Yes, very slowly. If you want to raise the humidity in a room, how do you do it? A pot of boiling water works much better. Lead is little different... actually, MORE difficult than water.

Lead melts at 621.43 (°F). At that point it's equivalent to liquid water (as far as our inhalation of it). Lead doesn't boil until 3180 °F. We are quickly melting it and it cools and resolidifies. You aren't at a risk of inhaling lead fumes unless you are smelting it. If you solder and you see fumes/smoke fly in the air that is not solder, that is flux. Flux is often resin based (check your bottle and your MSDS) and/or a chemical formula that will not poison you. You CAN irritate your sinuses and lungs, and cough for a day or two (at least the brand I use, Old Masters, can't poison me unless I confuse it's blue color for Romulan Ale and take a swig).

Now, as you work on it you get it all over your hands. That's why you must wash your hands immediately after working. You want to get lead poisoning, lick your fingers. I've cast lead into cames now, it didn't generate fumes (and incidentally my stovetop could barely melt the lead).

Some of us paint, and we use lead-based paints. Like a lampworker or glassblower using frit/powder, it is more of a concern. However, the powdered pigment isn't like flour and so on. It's a "heavy" powder, filled with glass fluxes and heavy minerals. While it is a powder, I've noticed minimal "floating dust" when I opened the sealed jar. I take a palette knife's worth and put on a palette with no noticeable cloud. Of course then we promptly mix it with binders and mediums and such and it's never again in dust form. I do own a mask that I can wear if I am concerned (and I use it for my silver stain mixes, which DO like to make dust clouds). Otherwise... as rare as I actually mix a fresh batch of paint... it's not a serious concern for me.

Now, for three "real world" arguments. The owner of the local glass shop, a woman who is as generous with her knowledge as she is skilled at a workbench, discussed lead safety with me a few months ago after a Facebook thread made me panicky and I bought ducting to build a ventilation rig. She informed me that in 30+ years of doing stained glass she has occasionally had a blood lead level test run, and it has never shown anything abnormal.

In the aforementioned FB thread, the owner of a professional studio mentioned she had an employee once who did test for elevated lead. Turned out he hadn't been changing out of his work clothes at work, and had been driving home in them after being around soldering and lead 8 hours a day. THAT lead to an "elevated" level of blood lead! Not lead poisoning.

So, in an effort to maybe put this to bed, both for others and for my own paranoia, I just went to the hardware store three hours ago and bought a big pack of lead tests. Instant Lead Testing ("If it's red, There's lead!" it says. "If it's red, you dead!" I thought) by Lead Check. A pack of plastic tubes with two ampules you crush to mix the solution. You then apply it to surfaces and If It's Red(tm) You're gonna have a bad time, mmkay?

Test 1 - My computer desk. I do my pattern work on my computer and have been known to absentmindedly click print while working on glass. Oh, I also eat here and spend 10-16 hours a day near this desk. You can imagine why it was site number 1. I dumped yellow testing liquid all over the desk, several important keys, and the left button of my mouse. Not a hint of red.

Test 2 - Other common surfaces in my house. After all, as some people keep trying to say to us, lead vapors are floating around to kill us and everyone we love. My couch? Nope. My dining room table? Nope. If you are unfamiliar with my home, it's an open floor plan, no walls. Couch armrest, kitchen counter, all ok.

Test 3 - What the heck, is this thing on? Solder and my (paint-encrusted) palette knife. Both came back brilliant dark red (oddly the solder took several seconds and the palette knife's droplets turned red practically as soon as I thought about applying). I guess they work!

Test 4 - My workbench. I tried the surface of my primary work bench. Yellow!
Test 5 - The plastic top of my lightbox. Tried several spots, all yellow!
Test 6 - The side of a plastic storage thing bordering my solder area. Yellow! This is about 1' from my soldering area.
Test 7 - The wall bordering my solder area. Permanent yellow staining of the paint, a foot from my soldering area.
Test 8 - The steel coil holder for my soldering iron, less than 1" away from the hot tip of the iron when it's on. YELLOW.
Test 9 - Dragging the thing through every cranny and coil above the soldering iron in that holder. FINALLY got some pink.... at the opening of the holder, which I hit every time I put the iron away without looking right at it. I guess that makes sense.


Edit: Test 10 - Tested the ceiling above my soldering area in several spots on a 2' line above the bench. YELLOW.

So, in short: Don't smelt lead from ore, don't lick your fingers, don't confuse your gin and tonic with your flux and wash your hands, kids!

A&S Day... something: Casting Cames

My last planned obstacle: casting lead cames to use. I've been trying to get a mold to work for a while now. Soapstone would be much easier, I think, but the documentation I have is after the period of my panel. The documentation I have from before it says the molds should be either iron or wood. There is no way I can forge an iron came mold, so wood it is.

A quick note on terminology, as I was taught and use. The two broader surfaces of the came's "H" that are visible are leaves. The lead portion connecting them, which is directly between the pieces of class and cannot be seen, is the heart. 

A less quick note on safety: Lead (and other heavy-metal) poisoning almost always happens because of ingestion, not inhalation. If you get a whiff of fumes while soldering and it irritates your nose or gives you a headache, it's because of the flux compounds (which generally are not serious, but check the MSDS for your flux). Think of lead like water. If you have a cup of water, is it billowing steam in your face? No, it's in liquid form. Even if you heat the water a bit, its warm or hot water. It is quite possible to heat lead and not generate lead fumes. If you are boiling the lead, then you have a problem! At the hottest setting of my stovetop I could barely melt the lead. Still, I ran the vent hood on high. I believe this process is very analogous to soldering (which is melting lead), and soldering is pretty safe for a hobbyist. I know professionals with decades of stained glass experience who do not have elevated blood lead levels. A little research indicates that the temperature at which lead generates fumes is 800-1000 degrees hotter than the melting temperature during casting. That being said, a hot plate outside will not do you wrong, either. Remember that any tool or container you use for working with lead is contaminated and must be washed. If, like me, you use a pan on the stove do not reuse the pan for food. I highly doubt you could get it clean enough.

I started with some wooden blocks that I believe are intended as part of crown molding. At the hardware store I verified they were relatively flush when squeezed together (such as by a clamp).

At first I tried free-hand carving the grooves. That sort of worked but I realized it was going to be impossible to keep them lined up the whole length without the leaf-grooves being wider than I wanted.

Going back to primary sources provided an answer. Soaking string in paint, laying them out, and then pressing the other board onto the first. This would create two sets of lines that should line up again. I found this to be fairly difficult, however, because I was trying to keep the lines a uniform distance, and the thick yarn made a fairly imprecise line to then follow. Not to mention it rolled a bit when I was trying to line up the edges of the block too (probably unnecessary).

 This view of the clamped mold shows the difficulty I had with the period method.

I ended up using a precise rule and measuring in an inch from the edge of the block. I made a line, moved over about 3/8" and made another line. The idea was to provide a common reference point (the block edge) and, if my measurements were accurate, everything should line up.

I then used a handsaw to "connect" the lines on either end. This ended up more difficult than I initially anticipated because of the wood I used. It has a slight curve, so sawing the ends was easy but it took some patience to get the grooves in the center.

The boards after the grooves were sawn.

Another view

I had a mold for the leaves, but I needed to remove a little of the wood between the two grooves to put the heart between them. I tried several tools and didn't find an "easy" one to make this painless. First I tried wood carving chisels, which did almost nothing (they are a cheap set). Then I tried the thin edge of a large file, with minimal results. I then wrapped sandpaper around that thin edge and tried again with some progress. The only sandpaper I had available was relatively fine, however, so I think that impacted it.

Finally I used a set of smaller files, where I could use the crosscut broad surfaces, and they worked better than anything. I sat during a Blackhawks game and filed away material until I could feel a distinct difference. A bright light provided a good test as well:

When my former protege-brother (he was elevated, there was no falling out) taught me to cast with lead-free pewter, he taught me to use an electric crucible popular with sportsmen for making lead sinks. Another protege-brother had said that a cast iron skillet works just as well in a pinch. I purchased a cast iron skillet with nice little pour spouts for this purpose (If anyone comes over for breakfast I promise not to reuse it!). I placed a bit of scrap came into it and fired it up. And waited. And waited. Eventually, with the fire turned up as high as it would go without the igniter clicking, it worked.

Now, note that what I'm using for this is scrap and cast-off cames, usually heavily oxidized. The piece above was clipped from my "good" spool. Lightly oxidized, it is silver and pretty. Once I saw it would work, I threw in my much dirtier scrap pile:

As soon as I tipped the pan a little a lot of the above lead pooled together. The impurities are fairly visible and many "colors" appeared as time went on.

I couldn't take pictures of the actual pouring because at this point I required speed, accuracy, and two hands.

The top of my mold with some over-flow. It took less lead to fill it than I anticipated.

The bottom of the mold. I had set it on a block of soapstone so as to protect the surface of my stove from molten lead. 

Prying the mold halves apart was often a bit of work, and the first time it required an implement or two to assist. The results were somewhat ugly, though identifiable to me. The pictures may be hard to see because of how shiny the came was. It washed out the "depth" I think.

I immediately remelted the lead and tried again. I know that slight alignment changes can have big effects.

Much more identifiable. The heart did not fill in near the top, but there was a usable portion from this casting. I figured the mold might "burn in" a little and remelted this again.

This was my third or fourth attempt. I need to call it a night, so I've stopped here for the moment. Each casting has turned out better results than the one before it. I kept the came above, there is a section about 2" long that is usable, and I have 1" square pieces that will gladly take this piece of came! It's not much, but it's a successfully cast came from a wooden mold.

2014 A&S Faire, "Day" 5

Well, the panel isn't going to be done in time for Midlands tomorrow. I am quite a bit saddened by that, but it's for the best. I spent 20 minutes looking for the documentation I needed for a shortcut I was going to take (and it is totally period, but it's still a shortcut) so I could save two kiln firings and try to make it happen. I decided it was best to not do it, make it the way I wanted, and HOPEFULLY send it with someone to Pentamere in a few weeks. That way I can still enter it at Kingdom.

Anyway, it's in the kiln firing right now. I've applied one layer of grey mat to the pieces, and removed the vines and ivy leaves:

After I fire them all I will repeat it with a second coating overall, so there is no clear glass and two tones of grey. I'm slightly tempted to pick out highlights again, and have three tones of grey, accept the deviation from the "co-geo-contemporaneous" panels. Three levels of shading is period, but I don't know that it was ever used for grisailles.

Using wine as a vehicle for the paint is fascinating. I am using a somewhat sweet white wine as a vintner friend suggested (specifically a moscato, very specifically the sparkling moscato from Cooper's Hawk Winery). The glass is sticky as a result. The paint is hard to scrub out; I'm not certain if that is because of the wine or if I inadvertently added more gum arabic than usual. I suspect the wine because Elskus mentions using table sugar as a binder. I imagine the sweetness of the wine could be introducing the additional grip. Because it's what was more local, I'm going to try a test batch of paint with cider instead of wine, though that isn't documented in any of the period sources. It makes sense and I can imagine a Norman glazier using it happily.

In order to scrub the pieces out I'm having to dip my hog bristle scrub into wine. It's really more like I'm rewetting the paint and removing it with a paper towel most of the time, where as with water I usually brush the dry dust off. If I remember correctly vinegar is described as giving a hard protective shell to the paint that can resist water (and save on firings). This seems to have a similar effect. I'm also glad it's a little cold for bugs, yet; I think plenty of them would be interested in the sugar. At Pennsic I will likely need to paint with vinegar (citable) or forego it for water. The third documentable item in Theophilus is urine, which I don't intend to try soon.

I'm somewhat relieved that I'm missing Midlands tomorrow; as I go I discovered a few pieces that were painted incorrectly. At least one, a corner, I was talked into leaving alone. Two pieces ended up with no ivy leaves, however, and they stand out when taken as a whole. After I get the shadings done I think I will go back over some of the pieces and strengthen lines, add in missing leaves, etc.

Pieces with highlights and some without (yet). Ignore the blotchiness, it's excess paint on the "table" and not actually blotchy paint on the glass

A close up of the pieces being fired right now

A&S Faire Project, post 4... and porphyry!

Finished cutting the glass for my panel, got the key lines painted on as well. The first half is firing right now. Unfortunately looking at the picture I see a problem and I'll have to redo one of the pieces heh.

Showing some of the blue pieces in place

Key lines painted in

I decided to try and freehand paint it all, which is weird for me. I ALWAYS trace. It was fun.

Today I got two books in and a new sample of porphyry. Fortunately this looks like "the right stuff!"

The original pieces I bought look like they were intended for countertops or something:

The surface was completely smooth and didn't grind very well.

The new stuff is more like the color of "Imperial porphyry" and it arrived in rough chunks that do grind quite well. 

Finally....carving molds is difficult!

Period Silver Stain Trials

Finally, an update on my silver stain research. I'm entering this into A&S, and have enough information and pictures to make a worthwhile blog post.

I'll skip the long train of how I found my sources, following reference to reference until I narrowed them down. I found seven recipes for silver stains. One ended up being a poor translation of another. One was incredibly complicated and is intended as a ceramics glaze; while the recipe would probably work on glass, I really can't call it a glass stain.

The recipes and my notes follow:

Mappae Clavicula
This is a compilation of recipes for a tremendous variety of crafts. The core of the text was compiled around 600 AD. Versions have been found from 800, 1130s, 1200s, and a variety of fragments of the text.

Amongst other recipes for colored glasses is this:

"For staining [glass] sapphire, silver and sulphur should be set on fire together; afterwards from 2 pounds of clear mosaic glass and 3 ounces of the above-mentioned sapphire cooked together, you will make jacinth stones."

I initially missed this when I read my copy of Mappae. I didn't want blue glass. It wasn't until I read "European Stained Glass Around 1300 - The Introduction of Silver Stain" in which Meredith Lillich explains that in period people knew "sapphires" to be both blue and orange varieties of the same stone. Although this appears to be a recipe for a pot metal orange she provides a compelling argument that it may have been used as a stain, and that the furnaces available at the time were capable of reaching the appropriate temperatures.

I purchased a few small vials of powdered silver for my experiments. I also bought 2 pounds of 99.5% pure sulfur prills (pellets), apparently used for livestock typically. I ground the sulfur to a powder in my mortar and pestle. In the absence of proportions, I mixed them equally.

I wasn't sure what "set on fire together" should mean precisely. I put them in a pan I was planning on throwing away anyway, and set them on low heat. Holy cow! The sulfur melted quickly and the whole thing became a black tar-like mess. I couldn't figure out precisely how I was to use it, and decided I would grind it back into a powder.

I believe the sulfur and silver are reacting to create silver sulfate. I'm not sure what reaction would happen alone that couldn't happen in the kiln, so I went ahead and made a second sample that would not be heated until in the kiln.

In my previous post I tested pure silver sulfate and the effects were apparent, but not this strong!

Slide 1: "cooked" MC formula. Slide 2: "raw" MC formula. Fired to 1000 degrees.

A closeup of the "raw" MC formula, 1000 degrees. 

This formula created a beautiful orange stain, exactly as the formula described and Lillich predicted. I believe the irregular coloring has more to do with my crude preparation than with the mix itself.

The Lapidario of Alponse the Wise (Alphonso X) of Spain

The Lapidario is the text by which Lillich (and Ken Leap, possibly from her research) speculate that silver stain truly became known in the West. It is a text describing stones and astrological properties. 

The stone "Ecce" is given it's own section. Lillich explains the text in depth. An English translation of the recipe:

"The treatise also describes a stone called ecce, which was used in glassmaking, saying that it was found in Spain, “in a mountain, not of great height, which overlooks the town of Arraca, and is called Secludes. And the stone is of an intense black colour, spotted with yellow drops. It is shiny and porous, brittle, and of light weight …; and if it be ground up with honey, and the glass be smeared with it and submitted to the fire, it dyes the glass of a beautiful gold colour, and makes it stronger than it was before, so that it does not melt so readily, or snap asunder with such ease.”

The Arts and Crafts of Older Spain, Volume II (of 3), by Leonard Williams

Lillich explains that the names given are incorrect and explains this is actually the city Guadalajara. She identifies the stone as silver antimony sulfide, or pyrargyrite (Ag3SbS3). This is known as red silver.

Further research on my part shows that this is not the exclusive mineral source. Proustite is a mineral that is visually indistinguishable from pyrarygyrite. They are isomorphous, meaning they have the same crystalline structure and essential composition. The difference is that where pyrargyrite has antimony, proustite has arsenic. The test needed to distinguish the two substances was not developed until 200 years post period. 

I purchased samples of both rocks. Further research and pleading from friends turned up that antimony is much safer to powder and heat up. Even though I was using tiny amounts of the mineral and it was VERY unlikely to be dangerous, I used proustite for my test.

I smashed the red crystals into what I initially thought was a sufficient amount of good size. The powder stained quite well, but my sample is very small and isn't visually impressive:

Slide 3: Lapidario formula featuring proustite, fired to 1000 degrees. 

The Marciana Manuscript

This painting text comes from the early to mid 1500s. The formula given is:

"If you wish to make a beautiful yellow colour which may penetrate into the glass, grind some silver leaf with a little honey and water, that it may hold together; then wash it in water with the fingers until it is well purified, in the same manner as powdered gold is treated. Distemper this silver with gum water made with soft water, dry it, then heat it in a furnace as before, and it will become very beautiful, &c"

I took silver leaf and tore it up a bit before starting to grind it in my mortar and pestle. My initial thought is that the honey is there to help give the leaf some body and grind it up. It makes sense that you would then wash it off. I used gum arabic and water to apply it to the slide.

This stain ended up being tricky, and I tried it three times. It's a known fact that stain takes differently with different glasses, and that you have to experiment with each glass you want to use. I also knew from Leap's book that pure silver requires higher temperatures than silver salts 

The initial slide with this formula, fired to 1000, came back clean. The silver did nothing.

Slide 4: Marciana formula, fired to 1000. Aka, clean slide!

I had similar difficulties with the last two slides, and decided to try again. I fired them to 1300 degrees.

Left slide: Marciana formula at 1300 degrees....

It definitely stained, you can see the pretty yellow color in the picture (that's pure silver leaf underneath, not gold leaf). Unfortunately at this temperature the silver leaf fused to the glass and I haven't been able to remove it. So, I tried again, at 1150 degrees. The silver didn't stain.

I may continue to try and get this to work with this glass. It MAY end up being that this glass gets soft at too low a temperature for any other result, however. I won't waste much more of my materials chasing it down with this particular glass, though. It appears when it works it will be a beautiful pale yellow.

Brussels

The Brussels manuscript is actually slightly post-period, from the early 1600s. It was very easy, however, so I included it:

""The yellow is made with silver, copper, and a little yellow ochre, the whole ground up together on a plate of copper.""

Hah. Easy. HAHAHA. Foolish glass geek.

This formula is the second slide in both of the two preceding pictures. You will notice it makes a beautiful color as well. Unfortunately the minerals fused to the glass in most of my samples. 

Bottom center: Brussels at 1150. Above it, Brussels at 1300.

Center/slide 5: Brussels at 1000. Clearly staining the edges!

This stain is proven to work, but I'm having difficulty getting the mineral residue to come off the glass. Lower temperatures for longer time makes sense, seems to be how it would have been done in period (they certainly didn't have an electronic controller on an electric kiln!) That should allow the stain to set in the glass without the glass getting to tack fusing temperatures.

Antonio da Pisa

I was able to try this recipe thanks to Mistress Kirsten allowing me to use her copy of the expensive and rare French translation (there is no English translation of the original Italian). My translation:

"The yellow color

To get the yellow color, take the fine filings of money, that is to say, the Venetian money and grind this on a chip of porphyry, until it is fluid like water, then when you begin to paint, apply it on the white glass where you want it to become yellow, and mix it in the least with the liquid egg tempera."

I collect ancient Roman coins. There are millions of them out there, they are very common. Many of them are little better than slugs, and if they hadn't been found with better samples you would not know they once had any value. They are also very cheap. On that basis I initially considered buying a Venetian coin and grinding it as described. Then I discovered Venetian coins are not as common as the Roman ones, and if I were to do as planned I would likely be destroying a valuable historical artifact. Instead I researched further and discovered that a common coin had a composition of 1 part silver to 6-to-9-parts copper. I mixed a batch of stain in those proportions, and gathered egg yolk for tempera. I've never worked with tempera before, it makes a wonderful paint/stain base:

A great many painters are smacking themselves and saying "Well, duh." 

Some Venetian coins had much higher ratios of silver. Because of that I doped the mix with more silver. In the picture above the top compound has considerably more silver than the one below. Knowing that the visual differences might not be as obvious after firing, I wrote an "L" ("lower") into the original mix.

Unfortunately, as with the preceding two, I had issues getting this to fire at a temperature that didn't fuse the metals to the glass. BUT, it DID stain!

Ignore the thermal shock cracks, I got impatient around 400 degrees.. Slide on the right, da Pisa at 1150

Questions/Lessons Learned

My six samples, drying before being fired.

All six of the period formulas worked as a silver stain. This particular glass made it difficult to show some of them in all of their glory, however. Interestingly, to me, the earlier formulas (Lapidario, Mappae) were the easiest. They make or use silver salts which, if I understand Leap correctly, fire at a lower temperature. The later period mixes (Marciana, Brussels, da Pisa) rely on actual metallic silver and are more complicated. However, I think they give a yellow color instead of the orange/ambers of the earlier mixes. 

Many glass recipes I see suggest a methodology of long slow cooking which would be impractical in my electric kiln but make sense in a clay and wood-fired oven. That may help the later period formulas. I would love to try some test slides if I ever have access to, or make, a period glass kiln. Something I am mildly considering at Pennsic this year.

For sake of discussion, the "mistaken" formula comes from Timothy Husband's book cited in my previous post on silver stain. It seems clear to me he is quoting a translation of the Lapidario, but identifies the wrong rock:

"antimony sulfide and silver in a liquid suspension, diluted 1 part to 6-10 parts by some form of clay (brick dust, ochres, etc)"

Antimony sulfide is called stibnite. I believe this has been confused with pyrargyrite, however Husband didn't cite that passage or explain the source. Later in the chapter, however, he cites a translation of the Lapidario, suggesting that might be the source of his recipe as well. Antimony sulfide and silver is, essentially, pyrargyrite. I purchased a sample of stibite initially, before I read Lillich's text on silver stain. I may still try "stibnite and silver" in the future.

It may be after A&S season, but I am going to continue to work on these formulas, probably with other glasses and temperatures and with finer grinding of some of the minerals. I am pleased to know, however, that I have an immediately workable orange stain that is BEAUTIFUL and that I can give out at my silver stain class at Pennsic this year. 

2014 A&S Faire, "Day 3"

Good progress on the panel. I hadn't realized last week was going to include three 18-hour days. Im way behind and may use a PTO day or two this week to catch up. Some thoughts:

Moving around the table
I've got my "table" on an actual table. It's a lot more difficult to get a good cutting/viewing angle when you can't manipulate the paper cartoon or walk around the table. Doing this on a freestanding table would be more interesting.

Also, glass shards get stuck in the wood. That was a delightful surprise! Brush away all you want, you're probably going to need tweezers.

Grozing
Using a grozing iron kicks up glass dust. My research (as a nonmedical professional!) indicates silicosis is only a factor after prolonged exposure to large amounts of dust. I still might get a cheapy medical mask, I felt like my nose was a bit irritated.

Hot dividing irons
When I'm done with my dividing iron for an extended period, I quench the end in the goblet of water on my bench. Then I set it on a chunk of framing stock scrap that serves as an excellent stand, protecting my table or the pattern table.

Be careful where you set the rod. You can see the burned spot on the table in the picture above where I underestimated "black hot" iron. Also, the burns near my right elbow....

Cleanliness of glass
A rather subjective observation, but it seems like this glass cuts so much cleaner. Harder to make shelves in it when cutting straight lines. Very nice to work with!

2014 A&S Faire: Day 2

Today I learned I was way off base about the use of the grozing iron. I'm a little embarrassed to write this, but this blog is a place for me to track my findings, sources, projects, etc. I know others read it, and I link others here when something I've found may help them... but at its core it's my own record keeping.  So, today I learned that the grozing iron is not grozing pliers in a different shape.

It wasn't just the name that led me to think this, but a slight underestimation of the tool's capabilities. I understand and understood that the dividing iron acted as a glass cutter and running pliers in one; it creates a score that runs pretty much simultaneously. I thought that the grozing iron must be there for lines that don't quite break, or for glass that is leftover on a breakline. I tested the tool that way, running a score and confirming that, yes, it breaks the score.

However, that's not what gives period glass it's distinctive chewed appearance, and not why the tool is described as nibbling glass. Tonight I cut a few pieces of my panel with the dividing iron and noticed I could only cut some general shapes out, not the exact pieces I planned. I reviewed some notes, sources, and reconstructions from a tourist attraction in the UK and suddenly it clicked.

You are literally chipping away little bits of glass with the grozing iron. It uses brute force to chew bites off the glass, a description that suddenly seems a lot more on the nose when you are looking at all these tiny semi-circles taken out of an edge. I was also surprised to find that the tool is quite versatile. I can tear off large chunks indiscriminately, and I can also scrape slivers off. 

So, today I cut most of one blue/gold border. According to the museum notes these panels were silver stained. It looks rather even and its the entire piece in all of these borders, so I assumed it would be pot metal yellow. I'm trusting the experts, however, that these were stained.

A grozed piece in place

The border, missing two pieces

The picture above shows a side effect of using a dividing iron; There is a lot of uncontrolled cutting and breakage. Unfortunately it is very difficult to get the blue GNA glass I'm using here, and the clear mouth blown is expensive. I don't think I'm going to be able to maintain my goal of extensive period cutting. I will use it whenever I can, but I'm already accepting the fact I will have to use my modern cutter in many places just to avoid wasting hundreds of dollars of glass, some of which I can't even replace if I have to.

I'm saving the little pieces on the corner of the table to potentially make a small batch of vitreous paint. I have a late period formula that calls for iron shavings, which I have on hand. It will make for a fun little experiment. I don't have to worry so much about incompatibility if I am using the same base glass... I hope!

A close up of a piece while I worked on it, showing the characteristic nibbles

All in all today I got a first true appreciation for the work of a medieval glazier. I am making a 1 square foot scaled down version of a segment that would have been 4 square feet. If I do the math, and if memory serves, the entire window would have been 36 square feet. It was one of 5 windows in that portion of the church. One of several dozen windows in that cathedral. 

And they made it with a hot iron rod and a bar with a notch in it, in essence.

Ho-ly { ..... }

The enormity of it boggles my mind. They could do so much with so little in the middle ages.