Grade: Elementary

#3851. Keeping clay projects from drying too fast... Guru secrets s

Art, level: all
Posted Thu Dec 7 08:09:54 PST 2006 by Mike Strawn (
Everything the art teacher must know about clay and glaze defects, and firing
Art Teacher Ceramic Center, Asheville, NC USA
Materials Required: 2 plastic bags, 1 spray bottle for water
Concepts Taught: Tips for keeping clay workable over an extended period of time

The following discussion concerning how to keep clay projects in a moist and workable condition over an extended period of time is an excerpt from a more comprehensive interview recorded in November 2006 with author and master ceramic consultant Tim Reed of the Art Teacher Ceramic Center. I hope that you enjoy this segment as much as I have and think that you will find the information easy and most beneficial to integrate with your own clay work. It's my pleasure to welcome you now as we join this conversation already in progress..

MIKE: "... Tim, one of the biggest complains I hear around the clay studio, especially from beginners, is that they just can't seem to keep their clay work from drying out before it's finished. I know from personal experience how frustrating it can be when you are paying attention to one particular part of an elaborate piece for quite a while, only to realize too late that another part of it has already dried too much. Do you have any pointers as to how clay work can be kept workable over several days?"

TIM: "You bet I do. In fact, here's one of the best little tricks I know to keep things workable not only over a few days, but indefinitely! I've actually kept large works completely moist and workable over MONTHS using this technique. The beauty of it is that it's very simple and anyone can have success with it right away."

MIKE: "I love those simple little ideas that work so well! So, how does it work?"

TIM: "Well, I think the first thing that folks need to understand that, as far as the drying of clay work is concerned, WALL THICKNESS is really where it's at. Thicker walls, of course, tend to dry out more slowly than the thinner ones. So, the trick is to devise a way to keep a good moisture balance between ALL the thick and thin areas."

MIKE: "It's the shrinkage factor that really causes the trouble between two pieces of clay with difference moisture content, isn't it?"

TIM: "That's right, Mike. When the difference in moisture content between two areas of clay directly connected to each other becomes too great, the tension created can build to a point where they simply want to tear away from one another. I'd be willing to bet you that most people don't even realize that fully 40% of the TOTAL shrinkage that a clay body goes through occurs during the period between it's WET stage, and that of being LEATHER HARD. No kidding... and that's before it's even fired!"

MIKE: "There's no wonder why so much clay work ends up splitting seams and cracking even before the bisque fire!"

TIM: "You got that right! And MOST of the splitting and cracking of clay work coming OUT of the bisque happen because of those exact same tension-creating processes. The whole point here is that the WAY in which clay work is handled through the wet to leather hard stage, and then directed on through the subsequent drying process, will generally become the determining factor in that work's ultimate survivability. The firing process has its own set of precautions, indeed, but most clay-oriented defects can be traced back to the PRE-fire stage of creation."

"Of course, the inexperience of a beginning clay student doesn't help matters since they aren't used to just how fast exposed clay can dry out. The area that they are focusing on might be doing just fine, but at the same time another area NOT being paid attention to is moving quickly toward becoming leather hard. Tension can build up fast between adjacent clay parts and, before you know it, a whole network of virtually imperceptible stress fractures can be created. Sure, everything LOOKS all right going into the kiln, but the results of that stress ends up glaringly obvious when the piece comes out."

MIKE: "OK, so exactly what can a person do to make sure that their clay work stays happy and free from stress during its creation phase?"

TIM: "Well, to begin with, the obvious the rule of thumb is that you should always be mindful to keep those areas covered in plastic that aren't immediately being worked on. That's always going to be a GIVEN while you're actually working on it. But then, when you're ready to give it a rest for a while, I've got a neat little trick to not only keep an optimal level of moisture in the clay, but also to put moisture back into those parts that might have gone a little bit too far."

"First, you need to get yourself TWO plastic bags that will be big enough to easily cover the clay work with a little room to spare. Those standard tall kitchen garbage bags or even shopping bags well... you know, the ones that Wal-Mart LOVES to supply you with so much! You also need a spray bottle... the kind that you would use to sprits a plant or use spray cleaner with."

MIKE: "Wait a minute! You're not going to be spraying water directly on the clay surface now are you?"

TIM: "NO WAY... That's about the best way I know to SETUP a cracking problem! As you know, dry clay absorbs water like a sponge. The LAST thing you want to do is spray it with an uneven pattern so that a lot of water is going into one area, but not in another, and the uneven pattern from a sprayer can easily work against you before you even know what happened.

No, the idea here is to create a humid environment for the clay to INDIRECTLY and slowly absorb moisture from and, in the process, re-hydrate itself as needed. You see, rather than spritsing water directly on the CLAY, the safer way is to spray the inside of one of your plastic bags and place it loosely over the clay work. That alone would help to wrap the clay within a fairly protective cocoon. But then, by spraying the inside of the second bag as well, and using it to seal up the first cocoon you just made, the clay piece ends up tightly sealed within a cozy little controlled moisture environment."

"The system works so well because of the fact that different moisture levels of clay will absorb additional moisture at different rates. You could place clay work that has a WIDE variety of moisture levels through it, put it into a controlled humid environment, and the result will be an equalizing of moisture all through the piece. This works especially well where there are areas that are both too wet AND too dry on the same piece. In such a case, the clay that is too moist will gladly give its moisture to areas that don't have enough and the whole process revolves around a neat little give-and-take experience until everybody is satisfied. The clay essentially "self-regulates" the amount of re-hydration each part needs. Fact is, this little bag trick serves as a "humidor" of sorts that can equalize the moisture of a fairly large piece quite nicely... sometimes even overnight."

MIKE: "Yeah, but that bag is going to have to touch the clay work SOMEWHERE. Doesn't the wet bag transfer too much water onto the clay wherever they touch?"

TIM: "Nope. For one thing, water always beads when it gets on plastic, so the clay can only suck in the bead or two that it contacts at any given point. I have never had any trouble with that. Of course, you have to make sure that the bag isn't wrapped tight around the piece, but only draped over it."

MIKE: "I love it! Simple... cheap... effective. How long would you guess it would take to equalize a piece that had some significant moisture differences? I mean, do you think it's possible, this technique, to actually bring a piece back to a workably moist condition that would otherwise have been considered a goner?"

TIM: "Well, Mike, I generally think that ANYTHING is POSSIBLE, but to answer your question, Yes. In fact, I have done it myself. Of course, every piece will come with its own set of requirements for what it needs to self-regulate that moisture. Allowing it to do so within its OWN time frame will be the key there. Besides, you would just end up shooting yourself in the foot trying to push it beyond its natural capabilities. All I can advise you to do now is to simply keep checking it each day and keep spraying the inside of the bag to make sure the clay has amply moisture that it can draw from. Just allow the clay to tell you what it needs... besides, working WITH the clay instead of merely trying to dominate it will always produce the best results!"

MIKE: "The bag trick is perfect, and I think he idea of respecting the clay is something that more people would find beneficial in their own art experience. So, before we move on, is there any more you would like to add to this topic?"

TIM: "Well, there is more that could be said here, but I think most people will get pretty far down the road with what we've already covered. There are actually two more really neat variations to our little bag thing here that are really effective and target more specific needs. One is what I like to call "The "Bucket O' Stabilization". I love that one. You could stabilize a remarkably moisture-challenged piece with that one!"

MIKE: "Perhaps you would be gracious enough to tell us about it another time."

TIM: "I'd be delighted, but as you know I've already got a whole series available about that stuff... wait, can I talk about that?"

MIKE: "Sure, I don't mind giving YOU a shameless plug! What I don't get, though, is why you would put together such remarkable collection of tips and then practically GIVE it away! I don't know about you, but if I thought a particular product would be the answer to just ONE big problem, I'd gladly pay as much that you're asking for your whole SERIES of problem solvers."

TIM: "Yeah, well... teachers, and everybody else for that matter, simply don't have time anymore to be weeding through the jungle of technical information out there. So my deal is to offer all the most effective tips and info for those who don't really want to wait for good results anymore.
, distribute it all from ONE source, and then put it out there so that the price doesn't become a factor in them being able to get it... even if their school won't buy it FOR them.

I don't know, Mike... as far as cost is concerned, I guess we all wish that other folks would just be fair in the way they deal with US. Besides, I don't think you really loose anything when your gift is for the right reasons... I guess I look at my project's success in larger terms than mere money."

MIKE: "And that's why I'm telling everybody know about your project. I know it will be a big benefit to a lot of people."

TIM: "Thanks... so what shall we talk about now?...