Decoding Delamination
This is a bit of a technical post but this is also just me researching what’s happening in my own studio. If you have anything to add to the content please feel free to comment below!
See those bubbles? Those awful, terrible, no-good, pottery-ruining bubbles? That, my friends, is “delamination”. I spent many a frustrated afternoon battling this inconceivable nuisance of deterioration without knowing what it was called. Eventually I stumbled upon an article by Steven Hill that, ever so casually, described and gave a name to the very pox in my midst.
See: Electric Studio: Making and Firing
Some background information here: I throw thin. I try to get something that is delicate and light yet bold. I also like to dip my pots in slip and carve through it to the contrasting clay below. Plus my timing is terrible. What does this mean? It means that I tend to get distracted by other projects or parts of the process and forget about my leather-hard pots until they are dangerously dry! The result is slipping mostly, but not quite, bone dry pots. Each time I made this inevitable mistake I would watch as a ring of bubbles would bloom around my pot, mortification building in my eyes. Any attempts to smooth out these bubbles would result in something akin to this:
Yes, it looks like a cute a little heart! But there were so many holes in my pots and so many questions in my mind…
How in the world can a hole like that appear in a previously solid wall, you might ask? This, sweet reader, is a prime example of the wretched “Delamination”. As written by Steven Hill,
Delamination can occur as the water penetrates the wall from both sides after glazing and rehydrates the clay, causing it to expand. If the wall is too thin, the clay can rip apart, leaving a void in the center of the wall with a corresponding bump and sometimes a crack on the surface.
An excerpt from Glazes and Glazing: Finishing Techniques
While Steven is specifically talking about once-fired pottery, I found the effects and rules he outlined to be true for dipping a pot in slip as well. Things like a change in clay body or certain ingredients that prolong wetness in a glaze can change how your pot handles possible delamination. It also seems to be a huge problem for porcelain users. One thing is for sure, though, dipping a bone dry pot in glaze or slip WILL cause delamination! One question being explored, beyond the “how” or delimitation, is why the clay reacts this way in the first place? One thing I’ve read, which makes sense to me, is that it’s very hard to rehydrate bone dry clay evenly. What may end up happening is that the outside begins to expand when wet while the core of the wall is still dry, thus pulling the two sides away from each other and causing the bumps and cracks. Porcelain may be the biggest purveyor of delamination because it has a smaller particle size than stoneware typically does. It ends up getting saturated much more quickly thus making it harder to work with when throwing, for example.
I found a lot of super interesting information from this forum discussion at Clayart.
After reading about my little monstrous, wall-separating friend I’ve begun to understand and appreciate more the science of clay, its molecular make-up and what that can mean to me. There is validity and importance being someone who creates with clay, but I think there is truly something dedicated and passionate about the people who move beyond that to truly understand the medium. We all talk about clay being “tired” or “thirsty” even “sexy” gets thrown around a lot in the studio! Clay is more than mud and minerals it is something with personality that is more alive than any other medium I’ve worked in! And as something that is alive it is something that begs to be studied for it can only push what you do further.
Further reading on Steven Hill’s once-fired process and technical thoughts on delimitation can be found here.
*This is a re-post and edit from my old WordPress blog