Ken Adams

A conventional casting slip (liquid clay used for casting objects in plaster molds) does not lend itself well to balloon casting: in my experience, the clay simply runs off the balloon. What is needed is something similar: a highly concentrated slip (containing as little water, and as much clay as possible), but one that also has gell-like properties that will allow the clay to cling to the latex. In other words, a 'bad', or 'failed' casting slip!

Creating a slip that adheres to a latex balloon is only one desired quality. The problem with a pure porcelain slip, is that it is very brittle when dry, which means that any vessel formed using balloon casting is very hard to preserve intact when the balloon is removed (or even deflated): thin areas of slip are too fragile. I cannot tell you exactly how many times I watched a beautifully textured vessel simply crumble before my eyes - but there were far, far too many occasions!

One solution I came up with was to treat the surface of the balloon in some way, to make it easier to remove it from dry vessels without causing terrible damage. For example, by spraying with silicone, or sprinkling and then spreading talc over a balloon's surface before applying slip. But neither approach is 100% reliable. In fact, care must be taken with silicone: there are ingredients in certain silicone sprays that 'attack' latex. Test your silicone first, otherwise you will find yourself with a facefull of clay as the balloon spontaneousy bursts ten minutes into your casting session!

The solution I have found is to modity the slip itself. I do this by adding what I call a matrix comprising a mixture of Elmer's Glue and Glycerine (in 80:20 proportions). The greater the percentage of this matrix in the resulting slip, the more flexible and strong it is going to be when dry. BUT, this comes at the expense of post-fired vessel strength, so in the ideal world one should add as little matrix as possible.

Armed with this special slip, and also aided by other tricks (such as adding paper or silk fibres to the clay), it is possible to extract balloons from even the most ridiculously structurally 'compromised' vessels!

Go on, GIVE IT A GO!