In the website photos, the blue glaze stops partway down the cup, leaving a band of bare dark clay. When your cup arrives, though, the blue may have travelled a little further, even leaving a rounded drop of glaze on the exposed clay.
It’s natural to wonder: did something go wrong in the firing?
As shipments gradually picked up again in late September, some customers asked us about this. We understand the reaction. Before we got into pottery, we used to see this as a defect too. Only after we began firing cups ourselves did we slowly come to understand how that drop formed. During glaze tests, we even tried to make it happen again.
That didn’t go quite as smoothly as we’d imagined.
We call these teardrop-like runs of glaze, set in place on the cup, “glaze tears”. They can be a distinctive part of a cup’s appearance. But where the drop stops, whether it has touched the kiln shelf, and whether the finished cup is damaged are separate questions. Looking at those details before deciding whether you like it tells you more than the words “handmade” alone.
That drop on the dark clay shows where the glaze has flowed
The upper part of a Sharing Cup carries the glaze colour, while the lower part keeps the texture of the bare dark clay body. In photographs, the boundary between them can look like a line that has already been drawn. In practice, the edge you see after glazing is not yet the edge you’ll see when the cup comes out of the kiln.
During glaze firing, the glaze materials react and gradually form a melt that can flow. On an upright cup wall, gravity can draw it downwards. As the cup cools, the shape left by that movement becomes fixed. Digitalfire’s explanation of glaze melting and fluidity goes into more detail.
So that blue drop comes from the glaze layer above it; the dark clay underneath has not melted.
How far it travels depends on the glaze composition, how thickly it is applied, and the firing temperature and duration. With a glaze that flows readily, a slightly thicker patch can push an otherwise neat boundary further down. A photograph alone, though, cannot tell you that a particular cup was definitely glazed too thickly or overfired. These are among the factors that makers need to adjust through repeated trials, as the technical guidance on runny glazes explains.
Stopping just in time and flowing a little further leave different results
One of the small cups this time has a glaze drop that stopped on the bare dark clay, with a rounded tip, without running all the way to the base. Pick it up and that little raised bead really does look like a tear hanging from the cup.
Another close-up shows glaze that has travelled further. According to our production records for this piece, the white area at the tip is a mark left where the glaze touched the kiln shelf.
A kiln shelf is the refractory shelf that supports the cups inside the kiln. If glaze flows onto it, the cup can stick to it; removing the cup can leave material attached or cause damage. Ceramic author John Britt’s article on protective kiln wash addresses situations such as running glaze. A kiln equipment supplier also explains how glaze can stick to a kiln shelf.
Put the two photographs together and the difference becomes easier to see: one shows the shape of glaze that has stopped flowing, while the other also involves what happened after contact with the kiln shelf. Calling both “glaze tears” doesn’t explain that difference.
If you’re holding your cup and wondering whether to contact us, start by identifying which situation applies:
- There’s simply an extra drop of glaze and you’d like to know what it is: take a photograph of the whole cup and a close-up of the drop so we can look at its position and shape together.
- The glaze drop has sharp, loose or flaking parts, the cup is cracked or leaking, or its base won’t sit flat: stop using it, leave it as it is and contact us. Don’t try to knock off or grind down the glaze yourself.
- None of those issues is present, but you just don’t like the way the glaze has run: you can tell us that too. You don’t have to prove something is a defect for your preference to deserve a hearing.
Photographs help us discuss appearance, but they cannot establish food-contact safety on their own. If there are concerns about a particular finished cup, its physical condition still needs to be checked.
If we like it, why not put a drop on every cup?
We’ve thought about that too.
During glaze tests, we tried to recreate that rounded tip. But a little extra glaze often didn’t make the same drop look better. It made the glaze run further and eventually stick to the kiln shelf. Sometimes, that extra distance is all that separates the small drop we want to keep from a glaze run we need to deal with.
The difficulty is that we can adjust how much glaze we apply before the cup goes into the kiln. Once it is firing at high temperature, we can’t treat it like a painting and wipe away the excess as soon as we see it running too far. Nor can we open a hot kiln just to rescue one drop of glaze. At that point, it would be the cup maker who needed rescuing.
So we have to wait for the next glaze test and adjust our approach. Our attempts to reproduce the effect are still continuing.
In our experience of opening the kiln, drops as round as the one on this small cup, stopping just where they do, are unusual. We haven’t counted their occurrence cup by cup, though, and being unusual doesn’t automatically make a cup better than the others. Part of what makes you look twice is that even the maker can’t arrange for the glaze to stop in the same place every time.
You can understand glaze tears and still prefer a cup without them
Honestly, we preferred the versions without glaze tears at first too. The glaze and the bare dark clay each stayed in their own area, with a neat boundary that was pleasing to look at. It was only after seeing more of the variations that came out of the kiln that we began to appreciate those less obedient edges.
Preferences can change. They can also stay exactly as they are.
Some customers particularly like the texture of running glaze; others prefer the whole area of bare dark clay to remain clear. Both preferences are natural. If your Sharing Cup arrives and the glaze tears aren’t to your taste, contact us to arrange an exchange for a version without them.
At the time of writing this production record, we don’t offer glaze tears for an extra charge or a service for requesting a particular glaze-drop shape. If you’d like a cup with an identical teardrop, the photograph cannot currently be treated as a custom design we can reproduce every time.
We’re sharing these photographs so you can become a little more familiar with the ways a cup might look before yours arrives. To follow a cup’s journey from liquid clay to the opening of the kiln, read our Sharing Cup production record. When choosing a cup, you can also tell us what sort of finish you like, then browse the Sharing Cup range for a shape that suits you.
We only meant to share a few photographs for an easy evening post, and somehow it turned into all this. The glaze-tear experiments can wait for the next firing. Tomorrow, there are still cups to trim.
