Gourds and Polymer Clay

How to Prevent Clay Breakage

Problems with Gourd Art? The Artful Crafter and its Readers May be Able to Help

[Photo credit: StockXchng/rishste]

Hi,

I was glad to find your page on Clay Crafting because I am having a really serious problem for which I haven't been able to get an answer!

I make Santa dolls with gourds and clay. Up till now the gourds have been totally covered with clay including Santa's face, hands, arms, clothing, etc. Most recently I have been sending some to ... a Santa dealer [in a more humid climate].

Suddenly we are finding a new problem with some of the larger ones. The clay is cracking open in almost all areas of the gourd base.

My question is what exactly is causing this problem? Is it clay shrinkage or is it the gourds' picking up the humidity of the area, swelling and causing the clay to literally "explode"?

I just baked one that I've had sitting here for a couple of months unfinished. I had a few cracks in the hat and fine ones in the beard but I'm thinking it was because it sat there for so long. On something like that I fill in the cracks with air dry clay, sand it or whatever, and do my finishing work over that.

No one could ever tell there was anything cracked. I may be wrong but I'm hoping if there are already little cracks and I fill them in like that, that will be the end to the cracking.

I am so at a loss as to what I can do to prevent the problem and I'm hoping you might have some experience with a situation like this. Other people use clay on gourds for various faces, decorations, and other things but don't seem to have this problem.

The difference is mine are completely molded over with the polymer clay.

Please if you have ANY ideas whatsoever, please pass them on. I am desperate at this point. I don't want to quit making these figures but I can't continue the way this is working out.

I appreciate any and all suggestions you might have. Thank you so much for your help.

Kathy

[Photo credit: StockXchng/13dede]

Your clay covered gourd figures are wonderful! It's difficult to diagnose a problem like this by mail. But I'm game if you are.

Gourd artists cover gourds with all sorts of material. As far as I've been able to find, all the media typically used (acrylic or oil paint, twine, wax, individual seed beads) have enough flex in the design even when dry to withstand the imperceptible swelling of the gourd that occurs when the container absorbs moisture from the atmosphere. The decorated gourds also frequently have openings which allow air to freely circulate so that moisture doesn't build to the breaking point.

Polymer clay is a terrific medium but it shrinks around 2% when baked and it becomes quite brittle with age. Both these properties make it more susceptible to cracking (than the other media I mentioned) if a gourd swells with moisture.

I found the following in The Complete Book of Gourd Craft by Ginger Summit and Jim Widess (Lark Books 1996).

"Clay can be used in many different ways to build up, cover, or otherwise extend the natural shape of a gourd. Many new kinds of clay are available in hobby and craft-supply stores today, but not all of them are suitable for adding to gourds. For instance, some clays need to be set with heat, and when the gourd is heated along with the clay its shell may become brittle and susceptible to cracking. Also, many kinds of clay shrink while drying and may crack or pull away from the gourd's shell. Therefore, look for clay that will harden slowly at room temperatures."

I think what you did with the paper clay to fill cracks is a good solution if you can keep the figurines around long enough and subject them to changes in humidity to induce (or test for) cracking. Cured paper clay has more flex than baked polymer. Some air dry clay brands claim less than 2% shrinkage. Creating openings in your design or in the base of each figure will help too.

If you want to experiment doing an entire gourd with paper or air dry clay, I have a couple of tips. Air dry clay dries from the edges in toward the middle; and thinner parts dry faster than thicker. Uneven drying can cause warping, stretching and even cracking - exactly what you are trying to avoid!

So large pieces need to be watched as they dry. You can mist areas that are drying too fast or cover such areas with plastic wrap to slow the process.

Did I tell you yet how much I love your gourd Santas? Best of luck in finding a solution, so you can continue making these delightful works of gourd art.

Debbie said ...

"I have had this problem with using clay directly on gourds as well. I now do my shaping and molding on the gourd but then remove it, bake it and the use glue to attach the face back on. I think it is because of what you said - the gourd swells and contracts due to moisture in the air. The glue seems to give with this shrinkage and expansion."

Barbara said...

"I myself am a gourd artist and the pieces that I use clay on I always use an air dry clay...preferably Amaco brand "Creative Paperclay". If you make sure your gourd is wet on the spot where you place your clay, you don't need any glue. If it is a heavy piece,(like a tail or beak)I fashion the piece, insert a piece of dowel and then drill a hole into the gourd, use a little crazy glue and insert the piece after it's dry. I don't have any problems as long as the clay has dried for at least 24-48 hours. If there are any hairline cracks I fill them with wet clay and wait again. Otherwise I paint or finish the clay and then seal it with Minwax polyacrylic waterbased sealer. It lasts and looks great. I hope this helps. Also make absolutely sure that your gourds are completely dried before you use them."

Hugs XX

Deb said ...

"Great advice as always Eileen! It's terrible to think of something she worked on so hard not holding up to time. I wonder if she puts a hole in the gourd like you mentioned?? I would think that would help and they do have that air dry clay. I hope we hear back from her if she tries any of your ideas ..."

Cyndi said ...

"I've seen gourds that have been covered by a very shiny almost plastic looking medium too. I don't know what it is, but I'm very curious."

Kim said ...

"This is a very interesting topic - I'm learning some new things here too - thanks Eileen!"