Get Ready to Build
Slab building can allow you to make pottery with very clean lines, including mugs, pitchers, and other items. Working with slabs is, as a whole, easier to master than throwing on the potter's wheel. There are some techniques you should know about before building:
For this project, you will need about a half to one pound of clay (preferably a mid-range or high fire stoneware), a potter's needle, a wooden trimming or modeling tool, and slurry or water. It is also helpful to have a jar or glass to act as a template, and a carpenter's square or a ruler.
Create the Floor of Your Mug
For a uniformly cylindrical mug, it is best to start with a circular floor. The easiest way to achieve this is to use a jar or glass as a template.
Remember that the wall will be attached to the top of the floor, so make the circle big enough to accommodate both the wall and the desired interior diameter of the floor. Your mug will be less likely to have problems with form and with cracking if you roll out the floor slab directly on a small cloth-covered board. In this way, you avoid stretching the wet clay, can easily move the mug around your workspace, and the cloth will help wick water away from the mug as it is drying.
Roll out your slab to an even thickness of about one-quarter of an inch. Place the jar in the middle area of the slab. Either cut directly around the jar or, to avoid losing the circular quality, gently impress the jar slightly into the clay.
Using the potter's needle of a fettling knife, cut out the circular floor. Gently peel away the excess clay. We are now ready to make the mug's wall.
Create and Attach the Mug's Wall
Roll out a slab of the same clay body to the same thickness as the wall slab. To determine the length needed, loop a piece of string around the floor to measure its circumference. This will be slightly longer than the slab needs to be, but it is much easier to trim excess clay away than stretch the clay to fit. Determine how tall you want the mug to be.
Use a ruler or a carpenter's square and cut a rectangle out of the middle of your slab. The long sides should equal the floor's circumference and the short sides should equal the mug's desired height.
If the clay is soft, allow the wall slab to stiffen a bit before doing anything else. You do not want it at leather hard, but you do need it to be able to support its own weight.
Once stiff enough, score and slip around the top edge of the floor and around one long side and both short sides of the wall. Attach the wall to the floor, then the sides to each other to create the cylindrical shape of the mug's body.
Weld all joints together, both on the exterior and the interior of the mug. If needed, add small coils. Welding the interior may work better if you lay the mug on its side and use your work surface to support the wall.
Create and Attach the Mug's Strap Handle
For a strap handle, roll out a slab that is the same thickness as the floor and the wall. Using a ruler, cut out a slab that is the desired length and width of your handle, taking shrinkage into account. Other possible types of handles include coiled and pulled handles.
Weld the Strap Handle to Your Mug
Once attached, weld the strap handle firmly to the mug's wall. Pottery is tough, but mug handles do take a great deal of stress. Make certain your joints are strong.
Once the form is complete, do any clean-up work needed. During this stage be sure to consider the mug's rim. Generally, slab-built rims need some rounding to be more comfortable against the user's lips.
Finish Your Slab-Built Mug
After your mug is completely bone dry, it is time to convert it from clay to ceramic in the bisque firing. Once bisqued, glaze it with food-safe glazes. The interior glaze should be glossy and the glaze on the rim should be thick enough to give a gently rounded, comfortable surface when the mug is used.
This mug was fired to cone 7 in an oxidation atmosphere.