Feeds:
Posts
Comments

Posts Tagged ‘leonardo da vinci’

Bronze horse on display at Adonis Bronze in Alpine, Utah

Bronze horse on display at Adonis Bronze in Alpine, Utah

As part of my unit on the history of chemistry, I wanted my students to experience an ancient art. I have written before that, in my opinion, there were three major threads that led to modern chemistry: Greek Matter theories (more on that in my next post), Alchemy, and Artisans. Some of the art forms and technologies invented during Roman and Medieval times are still practiced today in essentially the same fashion, such as stained and blown glass, ceramics, sword making and blacksmithing, jewelry, weaving and fabric dyeing, and some types of metallurgy.

Hoop Dancer, a bronze statue on display at Adonis Bronze

Hoop Dancer, a bronze statue on display at Adonis Bronze

We have some newer tools and a better understanding of how matter works, but in many cases the old techniques haven’t changed much. For example, a glass blower from the Middle Ages would have no problem working in a modern workshop. We have better heating sources for the glory hole and annealing oven, can use a blowtorch to keep areas hot, and have substituted wet newsprint for the smelly leather they used to use. But that’s about all that’s changed.

Blacksmith statue at Adonis Bronze, made with the lost wax technique.

Blacksmith statue at Adonis Bronze, made with the lost wax technique.

I did some searching and found there were several workshops in our area that do bronze casting using the lost wax technique known from antiquity, with a few modern additions. I arranged for my chemistry and 3D modeling students to tour Adonis Bronze in Alpine on Friday, Nov. 7, 2014.

Sketches of horses by Leonarda Da Vinci in preparation for creating the bronze horse.

Sketches of horses by Leonarda Da Vinci in preparation for creating the bronze horse.

Students were prepared by discussing how the lost wax technique works and giving examples, such as Leonardo Da Vinci’s huge bronze horse for the Duke of Milan, Ludovico Sforza, that was never finished. He had devised a method for making the horse in a single bronze pour, and he drew extensive sketches. He even made a full-scale clay model of the horse which stood 24 feet high. He was collecting the bronze for it when war broke out; the French invaded northern Italy and attacked Milan in 1499. The Duke was forced to melt the collected bronze down into cannons, but the French still won. They used the clay horse model for target practice.

Da Vinci's sketch for how he would pour the bronze.

Da Vinci’s sketch for how he would pour the bronze.

A 1977 National Geographic article on Da Vinci included sketches of the lost horse, and a retired American airline pilot named Charles Dent dedicated his art collection to the project. A foundation was created and an artist named Nina Akamu was hired. She used Da Vinci’s original sketches to create a new plan for the horse. Billionaire Frederik Meijer helped to fund the project, and two full-sized horses were cast in 1999, 500 years after the original was supposed to be done. One is at an outdoor museum in Grand Rapids, Michigan and the other stands outside the racetrack in Milan. A smaller scale version is located in Allentown, PA, the home of Charles Dent.

Completed horse statue in Grand Rapids, MI

Completed horse statue in Grand Rapids, MI

We carpooled up to the foundry and began in their main exhibit hall. We divided up into groups, and I handed out cameras to each group so we could record everything and eventually make a video.

Adonis Bronze foundry in Alpine, Utah

Adonis Bronze foundry in Alpine, Utah

The modern version of the lost wax technique has quite a few steps. First, an original model is built out of oil-based clay over the top of an armature, or wire frame. For larger sculptures, a smaller model is created then scanned digitally into 3D. It is scaled up on the computer, then a physical version is cut out of foam using a 3D milling machine.

Yours Truly being attacked by a dragon. It was modeled in 3D on a computer and cut out of foam with a milling machine at Adonis Bronze

Yours Truly being attacked by a dragon. It was modeled in 3D on a computer and cut out of foam with a milling machine at Adonis Bronze

Sometimes the foam model is all that is needed. For example, at last summer’s Fantasy Con in Salt Lake City, a 30-foot tall dragon was built out of foam pieces and assembled and painted. The dragon was designed and cut here at Adonis Bronze. They also made large swords and shields and other display pieces, some of which were in the hallways here.

Foam milling machine used to cut the pieces for the dragon.

Foam milling machine used to cut the pieces for the dragon.

Once the original model is done, it is coated in a silicon rubber gel to make a negative mold. That gel, colored blue, is coated in plaster to reinforce it.

Clay sculptures used as original molds for the bronze statues.

Clay sculptures used as original molds for the bronze statues.

A reddish-brown colored wax is melted and kept bubbling in vats. It is scooped up with metal pitchers and poured carefully into the silicon mold to coat the inside and make a thin layer. The final bronze statues are usually not solid, as that would take too much bronze. They are usually less than ½ inch thick.

Balboa Bars - vanilla ice cream dipped in melted chocolate and dipped in nuts or sprinkles.

Balboa Bars – vanilla ice cream dipped in melted chocolate and dipped in nuts or sprinkles.

The flexible silicon is then pulled away from the wax positive. Any imperfections are fixed and wax cups and sprues (spouts or channels) are added to direct the flow of the bronze to all parts of the mold. The silicon molds are stored for future use in case extra copies of the statue are needed.

Clay model for Wingless Victory statue.

Clay model for Wingless Victory statue.

To create another negative mold that will hold the hot bronze, the wax positive is dipped into a thin ceramic slurry which coats the outside and inside of the hollow pieces. The slurry-coated wax is then dipped in sand. The sand pot has air blown up through it so that the ceramic slurry can be quickly inserted and coated.

Silicon rubber mold for Wingless Victory

Silicon rubber mold for Wingless Victory

It’s kind of like making a Balboa ice cream bar at Balboa Beach in southern California. There, a chocolate or vanilla ice cream bar (like the wax positive) is dipped in a chocolate coating, then immediately dipped into nuts or sprinkles while the chocolate is still liquid. Here, the wet slurry is dipped into sand, then dipped into liquid cement and allowed to dry. This ceramic/cement negative mold is hard enough to withstand the hot bronze without cracking. Vents are also added so that air can escape as the bronze is poured in.

Vats of melted wax ready to pour into silicon molds.

Vats of melted wax ready to pour into silicon molds.

The molds are placing upside down in an oven and heated to melt out the wax, which is collected and re-used. This leaves a hollow area for the bronze. The molds are then placed into a kiln and heated to the temperature of the molten bronze, about 2100 ° F (1200 ° C). The bronze is melted in a blast furnace inside a balanced crucible. The bronze casters wear thermally insulated suits and carefully pour the bronze into the heated ceramic/cement molds.

Pouring hot wax into the silicon rubber mold.

Pouring hot wax into the silicon rubber mold.

Once the bronze and molds cool, the mold is broken off and the bronze pieces are “chased” – the cups and sprues are cut off along with any extra bronze that might have leaked around the edges of the mold.

Removing the silicon rubber from the wax positive.

Removing the silicon rubber from the wax positive.

If the statue is large and made from separate pieces, the pieces are then assembled together using welding torches and metal staples. Sandblasters are used to smooth the seams and staples so the surface appears continuous.

Wax mold after chasing, with the halves of the mold combined and cup and sprues (distribution channels) added.

Wax mold after chasing, with the halves of the mold combined and cup and sprues (distribution channels) added.

To get the right finish and colors in the bronze, the statue is sent to a room where chemicals (acids, bases, finishes, etc.) are added to create a desired color. Sometimes the color is created by heat treating – the bronze, which is an alloy of copper and tin, will take on a range of purple and red hues simply by heating areas to just the right temperature with a blow torch. The final coloration is called a patina. The surface is then waxed to preserve it from oxidizing.

Coating the wax with a ceramic slurry to make a negative mold.

Coating the wax with a ceramic slurry to make a negative mold.

The final step is to add a base, usually of wood or marble, then prepare the statue for shipping and display.

Coating the slurry in sand. Air blown up through the sand to make it easy to coat the slurry.

Coating the slurry in sand. Air is blown up through the sand to make it easier to coat the slurry quickly.

It was a fascinating tour. I asked many questions, and got some great things on tape. They were not doing a bronze pour today, so at some point I need to get back to videotape that. They were nice enough to give me a packet of photos showing a statue of a woman going through the entire process. I scanned the photos and created a Powerpoint slideshow, which I am linking to here: Adonis Bronze slideshow-s

Cement-sand-clay slurry casts with wax inside. Notice the sprues that distribute the bronze once the wax is melted out.

Cement-sand-clay slurry casts with wax inside. Notice the sprues that distribute the bronze once the wax is melted out.

I am amazed at how many of these steps haven’t really changed from Da Vinci’s time (or earlier – some examples have been found in Israel that date to 3700 BCE). He did not have silicon rubber to make the negative mold from the clay, and so a direct technique was used. A core of clay was dipped in wax and the wax carved into a final shape.

Melting the wax out of the mold. This is the

Melting the wax out of the mold. This is the “lost wax” step. It leaves a hollow for the bronze to fill.

Sprues were added and the whole thing buried in a compacted sand pit with drains in the bottom. The wax was melted out by heating the sand from the sides or underneath, leaving a clay core supported by rods and a hollow negative space surrounded by hot sand. The bronze was then poured in, allowed to cool, and the whole statue dug out and filed and polished to its final shape. How Da Vinci would have accomplished this with a 24-foot high horse is beyond me.

Pouring the molten bronze into the pre-heated ceramic/cement molds.

Pouring the molten bronze into the pre-heated ceramic/cement molds.

At some point I hope to find a way to duplicate this process on a small scale using pewter or another alloy with a low melting point. I know small heated crucibles are available to melt pewter. Now all we need is a way to re-create the lost wax technique to make the molds.

Assembly of the Wingless Victory statue. Large pieces are welded and stapled together, then smoothed and sandblasted to remove seams.

Assembly of the Wingless Victory statue. Large pieces are welded and stapled together, then smoothed and sandblasted to remove seams.

Perhaps we can carve the sculptures out of wax and coat them with plaster-of-Paris, then melt out the wax. We would have to be careful to not dehydrate the plaster. Or perhaps the molds could be made with wet clay and fired, then filled with metal. It would be a challenging project. If anyone has done something like this, please let me know.

Acids, bases, metal salts, and heat are used to create different colored patinas on the surface.

Acids, bases, metal salts, and heat are used to create different colored patinas on the surface.

Wingless Victory on display in the showroom at Adonis Bronze

Wingless Victory on display in the showroom at Adonis Bronze

Feather dancers, a statue on display in the showroom of Adonis Bronze.

Feather dancers, a statue on display in the showroom of Adonis Bronze.

An elk and Mark Twain. Notice the differences in the patina colors on the elk.

An elk and Mark Twain. Notice the differences in the patina colors on the elk.

Other clay statues. They are built around a wire and metal rod armature.

Other clay statues. They are built around a wire and metal rod armature.

Read Full Post »

Self portrait of Leonardo da VInci

Self portrait of Leonardo da VInci

Ever wonder where ink comes from, how it was invented and how it is made? I do. Most of the ink we use today for printing newspapers or drawing is called “India” ink (although it was invented in China). It uses carbon black, or soot, for the pigment. But before this ink formula reached Europe, artists and scientists used a type of ink based on iron known as iron-gall ink.

Original drawing by Leonardo da Vinci using iron-gall ink

Original drawing by Leonardo da Vinci using iron-gall ink

In July, 1984, I had the opportunity to travel to Europe with my family. Among many works of Renaissance art, I saw a display of original drawings by Leonardo da Vinci in Florence. There were plans of statues he was commissioned to cast, sketches of human anatomy, and designs for fantastic devices. One thing that caught my eye was his artistic ability; how well he could draw directly using pen and ink. I remember wondering where he got his ink from, which had turned brown with age. Now I know the answer, and I’ve turned it into one of my favorite activities in chemistry.

Alchemical manuscript by Sir Isaac Newton, at the Chemical Heritage Foundation

Alchemical manuscript by Sir Isaac Newton, at the Chemical Heritage Foundation

Iron-gall ink was used for about 1400 years and only lost favor in the mid 1800s when India ink replaced it (because it was cheaper and easier to make and produced a more consistent, longer lasting black). But there’s something to be said for the artistic variety and richness of the shades of iron-gall ink and how it has oxidized with time. The manuscript shown here was written by Sir Isaac Newton with his own homemade ink. It is one page of 24 in the possession of the Chemical Heritage Foundation in Philadelphia and is a series of notes he made on his alchemical experiments (yes, Isaac Newton was an alchemist; in fact, he wrote far more pages on alchemy than he ever did on physics).

Isaac Newton's recipe for iron-gall ink

Isaac Newton’s recipe for iron-gall ink

Newton also left behind his own recipe for ink, as seen here. He started out by collecting galls off of oak trees. These galls are formed when a species of wasp lays an egg in an oak bud, which causes the oak to form a rounded ball or gall around the developing wasp larvae. As Newton’s recipe shows, he soaked the galls in strong ale or beer for a month along with solid gum Arabic. The rotting oak galls would produce tannic acid. The gum Arabic, which comes from the gum of acacia bushes in northern Africa, is used here as a binder to help the ink stick to the paper and keep the pigment in suspension, as well as make the ink have a better flow and consistency. Newton would then mix the tannic acid/gum solution with copperas. This is a chemical with a greenish-blue color that was mistakenly thought to contain copper (hence the name) but is really iron (II) sulfate. The mixture of the iron (II) ions with the tannic acid produced a rich dark brown-black suspension ideal as an ink pigment.

Chemistry students making ink

Chemistry students making ink

The question is how to make similar ink using modern equivalents. I’m not about to soak oak galls in ale for weeks; as it turns out, tannic acid is readily available from strong tea. The iron (II) ions can be produced from steel wool by boiling it in vinegar, filtering the solution through wet filter paper, then adding a small amount of 3% hydrogen peroxide. The trick is to not oxidize the iron too much, or you’ll get too much rust (iron (III) oxide) and your ink will be too brown. Getting a nice black color with just a hint of brown is ideal. If the ink is too thin, then it can be left out to evaporate and make it more viscous. A few drops of gum Arabic are added at the end. You can buy gum Arabic in most craft or art supply stores. If you add too much, the ink will be too glossy when it dries. I originally came across this procedure in ChemMatters magazine (“An Iron-Clad Recipe for Ancient Ink” ChemMatters, October, 2001) and have tinkered with it over the years.

Chemistry students drawing illustrations with their own homemade ink

Chemistry students drawing illustrations with their own homemade ink

So what is the ideal recipe to make the darkest ink? That’s the inquiry part of this lab. I have the students experiment with different formulations to see what the best ratios of steel wool, vinegar, hydrogen peroxide, and tea would be. They also change the time that the steel wool/vinegar mixture is allowed to boil. They begin by learning the old recipe using oak galls, then learn the modern equivalents. From that, they identify variables to test. These factors (or ingredients or procedures) can be listed on the board and divided into comparison groups. Small groups of 2-3 students are assigned to each possibility, such as one group testing the amount of steel wool and its gauge, another testing the strength and amount of the vinegar (kitchen strength or glacial acetic acid) and how long to cook it, another group can test the hydrogen peroxide amount, and another the strength and amount of the tea to add. All of these results can be compiled and compared to create the ideal recipe for making the darkest ink.

Using a traditional drawing pen with homemade ink

Using a traditional drawing pen with homemade ink

The procedure outlined in the ChemMatters article calls for students to boil 200 mL of water, then soak two tea bags in it for five minutes. Meanwhile, a steel wool pad is placed in a beaker with 100 mL of vinegar and boiled for seven minutes. The solution is filtered and cooled to room temperature, then 1 mL of 3% hydrogen peroxide is added. The grayish solution turns a reddish brown as the some of the iron (II) is converted to iron (III) ions (during our Intersession class, I had students use 10 mL of the hydrogen peroxide by mistake and their ink turned too brown). The iron solution and the tea are both added to small cups or vials in equal amounts and stirred together. A few drops of gum Arabic are added. My experience using this recipe produced rather anemic gray ink. As you can see from the illustration of Cai Lun (the inventor of paper) by Evan, with some experimentation you can achieve a very nice dark ink which compares favorably with India ink.

Cai Lun, the inventor of paper. Notice how rich and dark the ink is.

Cai Lun, the inventor of paper. Notice how rich and dark the ink is.

Of course, what my students have done deliberately in one class period took people during the Middle Ages centuries of trial and error to develop, and even by Newton’s time, everyone still had their own recipe. As you can see from the manuscript page, his was a good formula and made dark brown-black ink that has held up well for almost 400 years.

Zach practices daring Elvish calligraphy using homemade ink

Zach practices daring Elvish calligraphy using homemade ink

Once my students create good ink, they go farther and use traditional drawing pens to create illustrations related to the history of chemistry. They pick a material to research, such as glass or steel or armor or stained glass or paper, write up its history and manufacturing, and create their own illustrations with the iron-gall ink. I am showing some of these in this blog. We’ve tried different formulas. In the Intersession Science and Art class I taught in March, we cooked the steel wool for too long in the vinegar and got too much iron (III) ions, or added too much strong tea. The result was sepia colored ink instead of dark black, as shown in the ladybug drawing.

Illustration of armor by Sebastian using iron-gall ink

Illustration of armor by Sebastian using iron-gall ink

Try it out for yourselves! Make sure to use uncoated steel wool. You can get it easily at a hardware store. The other chemicals are household strength and readily found, except for the gum Arabic. Most art supply stores do have bottles of this. It is a bit pricey but a little bit is all that is needed. Two bottles should be enough for a class of 30 students. You will also need some bottles or phials to store the ink (it will last a long time and can be reconstituted with water if it dries out), drawing pens and Bristol board illustration paper, which will be the largest expense of your lab.

Illustrations from my Intersession class where the iron was overly oxidized and turned a sepia color.

Illustrations from my Intersession class where the iron was overly oxidized and turned a sepia color.

As an initial demonstration and “hook”, I use a traditional quill pen and some parchment paper to show how it used to be done. I also demonstrate writing Chinese characters (tsz) using ink sticks, inkwells, traditional maubi (drawing brushes), and rice paper. I’m not very good at drawing tsz, but at least I can show how to hold a maubi and use ink sticks (which are not iron-gall ink – they are “India” ink based on carbon black bound together in stick form, then rubbed with water in an ink well). The “love” character shown was drawn by Miyuki, a Japanese exchange student, on parchment.

Illustration of plate glass making by Nicole

Illustration of plate glass making by Nicole

Drawing of Aristotle using iron-gall ink. I did this as a demonstration project for the chemistry students.

Drawing of Aristotle using iron-gall ink. I did this as a demonstration project for the chemistry students.

Illustration of Chinese fireworks by Richard, made with iron-gall ink

Illustration of Chinese fireworks by Richard, made with iron-gall ink

Alec's Anime drawing. Behind it are pigments we made for watercolors. Stay tuned for that post!

Alec’s Anime drawing. Behind it are pigments we made for watercolors. Stay tuned for that post!

Read Full Post »