As part of an effort to launch a small home-based business, I'm in the process of designing and building a themed drink coaster. I've identified specific needs for the base of this coaster and I'm considering using ceramic to meet those needs. As I have no experience working with ceramics or clay, I was hoping to describe what I want to accomplish and solicit your advice.
Each coaster will consist of two primary components- a thin concrete upper portion and a (potentially) thin ceramic base, with a piece of cork glued under the ceramic for tabletop protection. I've been working on the concrete part of this for several weeks and have about got that where I want it, so now I'm considering the base. I considered cork for the entire base but it's not really as sturdy as I want, and could potentially come apart in chunks, and wood is going to react poorly to repeated exposure to dripping condensation from mugs/cans/bottles, etc.
The outline of the ceramic would mimic (and be larger than) the outline of the concrete piece; think of the outline of letters that form a word, so it won't be a simple square or circle.
In addition, there would be a recessed area in the ceramic for the concrete top to set into. This 'nesting' will help support a somewhat brittle concrete shape. The thick outer portion of the ceramic would be 1/4" thick and the recessed inner area would be ~ 1/8" thick.
I want a material for the base that will be rigid, absorbent, dark gray / black (to provide contrast to the light color of the concrete) and something I can work with in my basement without requiring space for a bunch of new equipment. The pieces would be kiln-fired by some local vendor.
I'm supposing this would be similar to creating a flat tile, so it seems like it should work. Some of the questions on my mind are:
What would be the advantages / disadvantages to using pressed clay vs slip poured into an open mold?
What are the steps to making an absorbent ceramic? Is it just leaving out the glaze / firing process at the end? Is there a particular type of clay thay would work best for this?
What's the best way to get the desired dark color?
The recessed area in the finished ceramic piece needs to be exactly the same shape as the concrete piece that sets into it, so how do I factor in clay shrinkage to get to that point?
Any information you can offer to assist me in my endeavor is greatly appreciated!