Sunday, May 31, 2015

More Period Beadmaking Experiments

Two weekends ago I went to Ysmay & Mael Eoin's house to make beads in their back yard using the coal and firebrick fireplace I first experimented with in early may . I was going to try to do this myself, but luckily Astrid stopped by to watch and her help ended up being invaluable. Some notes from our experiments are below.

1. More than one person is needed. Two or preferably three people work best. While, since I have the air mattress blower, I don't need someone to constantly work the bellows for me there is still a lot going on when making beads (tools get lost and are needed, and sometimes you want to change up how much air is being blown into the kiln). An assistant is necessary.

2. Having three people available, one to help with situation awareness (and take pictures) is also important. As they do on occasion, a small piece of charcoal popped out of the fireplace. It landed about 5 feet away, beyond our field of vision, so we did not catch it as early as I would have liked, and some of the mowed  grass still on the lawn started burning. It was quickly put out, but it reinforced the need for more eyes and an increased attention to safety when doing these experiments.

3. Continuing on the issue of safety a few other thoughts include:
--making sure there is no dry/dead grass around the area we are working.
--wetting down the area around the furnace
--having a very large bucked of water available (in addition to the fire extinguisher).
--making sure the work area around the furnace is clean and not to cluttered with tools

4. 120 COE glass is amazing. We tested 104 COE glass and the fireplace  was hot enough to melt it, but the 120 COE Satake lead glass I purchased worked *SO* much better. A higher COE means the glass is softer and easier to manipulate. We had beautiful coils of glass form when we wound the glass onto our mandrels. At this point, I can very generally document leaded glass in period using articles from scholar Julian Henderson, who writes a lot about ancient glass. I'll have to look into this a bit more before writing up formal documentation to figure out how leaded glass is different from regular soda-lime glass, and exactly where and when this glass was found in period.


5. I made a melon bead (which I also did in 104 COE, but it was easier with the 120 COE glass), and new for this experiment, I tried and successfully made a dot bead! I suspect this would be more difficult in the open fireplace using 104 COE, but I'll have to try it some time to see. As I pulled away from the base bead when making my dot, the little tail of glass got cool quickly, so I had to try wrapping it around my glass rod, and keeping it close to the fire so the little tail of glass would flame cut itself. (I think i need to take video of this sometime!)



6. I also successfully melted some of the 120 COE glass in an iron crucible (mimicking the iron pan found at Ribe), picked the glass up with a spare mandrel (called a punty), and used that to make a wound bead. This is a method that archaeologists (see articles by Torben Sode) believe was used to make beads. Interestingly, the glass also picked up some iron from the surface of crucible (perhaps the crucible needs to be cleaned out better before use). This was interesting because it slightly changed the color of the glass, turning the yellow a bit green when compared with the original yello color of the glass. You can see this in the pictures of some of the beads we made at the end of this post. The left most yellow bead is the one that reacted with the iron in the crucible.




7. Regarding the Fireplace: Making it one firebrick high (and not two like last time) seemed to work well. It took less charcoal to fill (although we still went through almost one bag during the several hours we were working). I did not mortar the bricks together, which allowed us to remove a brick and sweep out the coals when they got too ashy, and then we could use a coal or two to quickly restart the fire. I think were were back up and running in 20 minutes or so. Next time I might mortar three sides together (leaving the one open for ash removal). It was steady enough un-mortared, especially since we double layered the fire bricks, but i'd feel a bit better with it more secure. The copper pipe should definitely be mortared in place, as the hole we drilled was a bit to large for it to fit securely and it kept moving.


8. There was some interesting things happening on the bottom of the fireplace near where the copper pipe was. More so than last time, perhaps because the fireplace was smaller? I'm not quite sure what is going on here, but this may be similar to some vitrification near the blow hole described in a formally published experimental archaeology article (by Sode or Gam, I forget who). However, this was not something seen at Ribe, so it may point to a different furnace design. I will want to read up on this a bit more, and try to figure out what exactly is going on here. They did have some burned and darkened clay found on the hearths at ribe, so maybe this is the same thing?? The picture below is of the bottom of the furnace during mid-day when we cleaned it out.

The end of the copper pipe also started melting by the end of the day! Again, I don't remember this happening last time.



All in all, I learned a LOT from this day of experimenting!