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Paula Dahlskog och Linda
Mårtensson
Bäckedals folkhögskola (Backedals College)
http://www.forntidateknik.z.se/IFT/MNTarb/2000/glasparl/glasparl.htm
Translated from Swedish by Skadi of Three Trees (Kerstin Darsell-Peters)
Editor's note: This is a translation of an article posted on line at the above address. The original includes photos of the process that we did not include here to avoid copyright infringement. Please referr to the original for additional clarity.
PROLOGUE
We are both interested in the Viking era and gladly decorate ourselves with jewelry that is appropriate for that time. When we chose a project, we decided to make glass beads. This handicraft has interested us for a long time.
The goal of the project was to build an oven, make beads and to color glass. There was a trial to make glass beads in another project (MNT 98/99) but the result was not so good, so we started again with new contacts and other methods.
HISTORY
The oldest find of glass beads were dug up in Mesopotamia and are from approximately 2600 BC (Sode T, 1996).
In Scandinavia, glass beads became common during the Iron Age. Colored and uncolored pieces of glass and beads were imported from the south to the big ports where they were an important merchant item and could also be used as items of value. Local bead makers, who were wanderers or lived in the villages, used the glass pieces.
Based on grave finds, it appears that mostly women wore beads, often as a necklace or between the brooches on the woman’s dress during the Viking time. Beads were status symbols but could also have magical properties.
The Arab, Ibn Fadlan, mentions that the northerners valued the beads highly and paid well to give them as gifts to their women (http://viking.hgo.se, 99-01-02).
Throughout history glass beads have been highly valued. Even today one can see a beautiful bead necklace adorning a proud woman in the market square.
After reading about several glass bead projects (Andersson P, Grimble J, and Gjaerum H, 1999, Sode T 1996, Dybdal P, 2000) we figured out a building method that would suite us best.
The oven would have to be used many times and be easy to put away when it was not in use. We needed an internal support for the oven. K-G Lindblad welded four pieces of flat iron into a 35 x 34 cm rectangle (inside measure), sized to fit over a modern forge. On two sides we bent the flat iron that stuck out to big handles. These later turned out to be useful to shape the beads on. In the middle of every flat iron we welded round iron stock to serve as internal supports for the oven. We did not use birch or other wooden materials that would burn out when the oven was fired.
The next task was to select clay and sand. We used red and yellow “hojslev” clay, simply because there is a lot of it. We added beach sand to the clay in a 50:50 ratio to get a stable oven. The sand and clay were carefully mixed and formed to sausages about 8 cm in diameter and 25 cm long. Some of the mix we made into clay “glue”.
Now it was time to build the oven. The sausages were placed on the iron rectangular base and joined together. With the help of the “glue” we worked the clay around the round irons and rounded the bottom of the oven’s corners. When all clay sausages had been added, we had a 29 cm (outer measure) high oven with approx 5 cm (after firing) wide walls. On two of the sides we cut out windows: a bigger hole, about 13 x 11 cm (after firing) for putting in coal and working with the glass and a smaller hole for just working with the glass. We also built window ledges to put the glass on for heating it up. Using the Dybdal’s drawings we built a pocket on either side of the windows to cool the beads in. We also thought about building a cup on the top of the oven for the same use as the pockets, but decided that it would be difficult to use with the modern forge because of the low position of the out draft.
The oven was now ready to be fired. We lifted it onto the forge and filled it with charcoal up to the window ledge. The clay had not been dried at all, but according to Dybdal it would be fine to fire it if it was done over the forge. We used a weak air intake and lighted the forge. Big cracks occurred. We tried to mend them with clay “glue” without much success. After three hours the oven was almost dry.
We filled it with charcoal up to the top of the windows and increased the air intake. During the heating process the oven temperature was about 1150 degrees C. We did not measure the temperature again as the thermometer did not read above 1200 degrees C. The cracks became bigger but were now easy to mend. After another hour we closed the air intake and let the coal burn out. To fire an oven with our method took four hours plus the time it took for the coal to burn out. We did not allow the oven to dry, because this would have taken two weeks.
Next day we had an oven to make glass beads in. The cracks reoccurred and we had to fill them twice before we were satisfied. We can imagine that they fired glass beads ovens on a forge in medieval times too.
TOOLS
In order to make glass beads we first had to make the tools that we would need
later. We took two pieces of small-diameter round iron stock and forged a
smaller diameter end on each (tool 3 and 4). The idea was to be able to melt
glass on one tool and spin this glass into a bead on the other tool. To shape
the beads we used a piece of flat iron, about 70 cm long and 2 cm wide (tool 2).
We noticed during the work that one of the difficult moments was to get the bead off the tool. We made another tool for this. We started with a piece of round iron stock, about 50 cm long and 1 cm in diameter. One end was forged flat, split 1 cm and bent up 90 degrees (tool 5 and 6). That tool, it turned out, worked very well. Another tool we were using was an angle bar, which was forged into a spoon on one end (tool 1). We used it to melt glass when we added coloring to it.
We started by putting a piece of glass on the window ledge in order to heat it up slowly. If one moves the glass into the oven too fast, where it is 1300 degrees C, stress occurs in the glass and it may crack.. After a few minutes we put the glass into the oven using tongs. When it started to melt, we transferred the melted glass onto tool 3. The glass continued to melt on this tool until it was more viscous. Then we spun some glass onto tool 4. To make it easier to remove the glass beads later we dipped the tool in kaolin clay mixed with water in a 50:50 ratio. We got this idea from Fotevikens Museum where they made glass beads a couple of times. It was not that difficult to transfer the glass from one tool to the other and spin it evenly into a round bead.
After that it was time to shape the bead with the flat tool. You should work at or just inside the opening of the oven. If you remove the bead it will stiffen right away and if it is too warm it will stick on the flat tool. You have to try out what will be the right consistency to start shaping it. We got round beads when we rolled it on the flat tool, square or triangular beads when we pushed them against the flat tool. We also made beads that looked like a flower when we pushed the edge of the flat tool into different parts of the bead.
When we were satisfied with the shape of the bead it was time to take the bead from tool 4 using the forked-end tool. This is probably the most difficult task to learn. If you take the bead off too early it is too soft and the shape will be destroyed. If you wait too long it will be hard and gets stuck on the tool. You have to remove it at the right moment.
The beads have to cool very slowly so there won’t be stress in the glass or they will crack. The cooling is the most important task in the production. It should take 8-10 hours for the beads to get from about 400 degrees C to room air. We tried first to put the beads in the side pockets on the oven but this did not go as well as expected. Some of the beads cracked. Either the temperature was not high enough or we did not continue to fire the oven long enough. Instead we put the beads into small clay containers with lids and placed these on top of glowing charcoal. The beads cooled here. This method worked very well and the beads did not crack.
To make colored beads we bought colored glass. We also used crushed beer bottles and homemade colored glass.
The most interesting trial to color glass was with bone. Torben Sode mentions in his book that the calcium phosphate from bone ash makes a white color when light reflects from small crystals. He also mentions that the ash should be white. We scraped a bone to make a fine powder that we burnt with propane. No matter what we tried, the ash did not turn white. Instead, it had a dirty gray color. We used it anyway. In the spoon tool we put a pinch of bone ash with 1 tbsp glass. This was heated in the oven. When the glass melted, we stirred the mixture with a metal rod. The mass was transferred onto the rod and was taken out of the oven to cool slowly. The glass had an opaque bone-white color.
We also mixed copper oxide and iron oxide in the same way. Glass and two or three pinches of copper oxide made a beautiful dark green color. Glass and iron oxide became black with blue nuances. With smaller amount of iron oxide the color turned green with a little blue. Many beads got a greenish color where the glass had direct contact with some of the iron tools. Was there a discoloration reaction?
Using the different colors of glass, we made patterns on the beads. We tried three types. We melted different colored clumps of glass together and made beads with it. The result was stripes and unplanned patterns. In the second trial we took a one-color bead, heated it and turned melted colored glass onto it. A controlled pattern was made this way. The third trial we tried was to put a fine crushed glass on the window ledge. We rolled the heated bead in this. A controlled pattern was made this way too.
We made other small experiments too, with the motto: all ways are good except the bad ones.
CONCLUSION
The result of our two-week trial with glass bead making was successful. We built an oven that worked well and was practical. We made beads in this oven. Of about 150 beads, 15 turned out bad. After the trials the oven was in good condition for continued usage.
At the end of the two-week project, we had some time left over. So we tried different ways to make colored glass. We tried 3 colors. All were successful.
Satisfied and happy, we will continue with the glass bead making, with the wish not to use any modern techniques or tools.
BIBLIOGRAPHY
Andersson
Pernilla, Grimble Jannika, Gjaerum Helena. Glaspärletillverkning, MNT-
Projektarbete vår –99.
Dybdal Palle. Personligt brev, 2000.
Fotevikens museum. Muntliga råd, 2000.
Sode Torben. Anatolske glasperler. Forlaget Thot, Kobenhavn, 1996.
http://viking.hgo.se, 99-01-02
Copyright 2006 by Paula Dahlskog och Linda Mårtensson Translated from Swedish by Skadi of Three Trees mka (Kerstin Darsell-Peters) Posted Oct 2006
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