Dung-Core Vessel Making: Explained

This week’s post is by Museum Explainer Anne Rich.

You know you’re an Explainer when you leap at the chance to spend a free afternoon shaping slightly aged animal poop. The afternoon in question occurred on Tuesday, May 22, when the Explainers were invited to a core-forming workshop hosted by The Studio’s Resident Adviser, Bill Gudenrath. An authority on ancient glassmaking techniques, Bill helped us recreate the process of core-making.

Bill explains the history of core-formed glass vessels.

For all the non ancient glassmaking experts out there, a core is a form attached to a rod on which glass is applied to make a non-blown vessel. A core needs to be made out of a heat resistant and relatively porous material, because after the glass vessel surrounding it has cooled, the core is scraped out to leave behind a hollow space. Historically, the core was made out of clay and, the part that manages to capture everyone’s attention, animal dung.

The animal dung

The dung was allegedly used because it contained undigested grass and straw, which burned away when fired. While the clay and dung covered the heat resistant requirement, the small holes left behind by the grass and straw covered the porous requirement.

When explaining the content of the Ancient Cart in the Glass Collection Galleries, someone always grabs the core from the cart, and says “What’s this?” All of the Explainers, past and present, understand the feeling you get when you have to explain that they’re holding fired poop on a stick.  For the Explainers, core-forming has served as a sort of inside joke as well as a crucial glassmaking technique that is taught to us from the very beginning of our training. You can only imagine my excitement when I got the news that Bill Gudenrath invited us to make some new cores for the Ancient Cart. Still away at college at the time, my roommate thought I was insane when I tried to explain what I was going to do the week I got home. My parents produced a similar reaction when I told them my plans for May 22nd.

The core forms

By the time everyone had arrived at the Mold Room at The Studio, so had the ingredients. On one side of the sink stood the clay, and on the other side lay an ominous looking bag of unopened horse dung. Certain resources revealed that our supply of dung had spent the past few hours in the back of a hot car. It wasn’t until the bag was opened that two things hit me…1. The smell, and 2. That this wasn’t going to be a fairytale tea-party (with interesting tidbits of glassmaking history). We were embarking on a truly hands-on experience, one in which we would spend half an hour kneading a poop-like play-dough a few inches away from each other’s faces.

A job well done!

This was a bit trickier than expected, and most of us Explainers spent a relatively long time fashioning our cores into neat and historically accurate shapes. After an inspection, they were ready to be dried for a few weeks. We Explainers were invited back on June 14 to file them into their final shapes before they were to be fired in the kiln. I thought that it was a big deal to have to work with wet dung, but then I spent time filing dried cores. Powdered poop filled the air in the Technician’s Room which hosted the second half of our core-making experience.

Filing the core forms

Glamorous, right? In a weird kind of way, I think it was. Don’t get me wrong here; I’m so grateful that I was able to attend the workshop and engage in a process that I’d so frequently explained yet never seen.  We Explainers laugh about making cores, but we made them basically the same way they were made as early as the 16th century B.C.E. Glassmaking, though sometimes unsavory, is a process marked by centuries of tradition, and is just a part of what makes glass so special.

For more information on Museum Explainers, visit http://www.cmog.org/dynamic.aspx?id=242.

2 comments
Tom Kies II
Tom Kies II 5pts

Just out of curiosity, were these to be dipped or wound? I know both can be done, and I know CMOG has a video up showing the crucible dip. I'm a part time lampworker, so I'm more interested in them being wound, but I suppose if you have access to the pots it's much quicker to just poke them in.

mkritzeck
mkritzeck 5pts

Thanks for asking, Tom! The rods that these cores are attached to would be too short to introduce into a furnace (they are only a foot long or so). The core forms were made for the Explainer carts that we have in the galleries to help show the different historical processes of glassmaking, which include the cores being dipped, wound, or coated with several layers of frit. However, these cores will only be used as teaching tools.