1. Decide on Your Design
Unless you are painting your knobs all one color, you may want to sketch a few different designs on a piece of paper before you begin your project. Ideally, you will want to use a compass and get a good estimate of the size of the area you will be working with. It is best to draw designs to scale so that you know what kind of detail is possible.
2. Draw Your Design on Your Knob
The great thing about unglazed ready-to-fire ceramic knobs is that you can draw your design right onto the knob. Make sure and use a pencil. If you make a mistake you can just erase it with a regular eraser. In my opinion it would be best to use a 0.5 mechanical pencil. Here I used a 0.7 mechanical pencil and the lines are a little thicker than ideal. In addition, there is more smudging when you erase with thicker lead; however it still will work fine for my purposes.
In order to be consistent, I used a ruler to make my design. This may be time consuming, but in the end it is worth it because you will have clean lines and if you are doing more than one, then they will all be same. Another great bonus of drawing your design directly on your knob is that you do not have to erase them once you're done drawing. Just make sure to paint along the lines and cover them with paint, it also helps to draw lightly.
When you choose your colors keep in mind the overall look of the finished product. You will most likely want to use complimentary colors and keep the general color scheme consistent - using only warm colors (e.g. reds and yellows) or cool colors (e.g. blues and greens). On the other hand, depending on what look you are going for you can use your knobs as accenting tools and use opposite colors to give some interesting contrast. Opposite colors are those that are 180 degrees apart on the color wheel; common examples of opposite color pairs are: blue and orange, green and red, purple and yellow.
Once you have picked your colors, get your work station ready. Get an old cup for rinsing your brushes, some paper or plastic to cover your working area, a palette (or a paper plate will do) and keep a lightly moistened paper towel nearby so as to dab away any mistakes. While you paint use hard, flat, brushes for straight lines. As you can see the color gets much lighter as it dries; in addition the color of the paint will change pretty dramatically once it is fired - most noticeably it will be much richer. You should put 2-3 coats of underglaze. Make sure that each coat is completely dried before applying the next or else some of the not-fully-dried paint may "stick" to the fresh paint and expose the clay.
You can choose to paint the whole knob with a base coat first and then draw your design and paint it. However if you do this and make a mistake drawing, then when you erase it you have to be careful because you could easily erase some of the base coat. This may not be an issue if you are painting that area of a different color, but if not then it may end up being a noticeable "spot" on your knob. When you are done with the underglaze, you may wish to put a clear overglaze as a final coat. This is not necessary, but makes your knobs shiny and also helps a bit to make your work last.
Whether or not you should put clear overglaze is more of a style decision - would some glisten on your knob look better on the finished product or not? Here is a piece that uses the contrast the different look and shine the overglaze gives the final product. On the left the overlaze was used while on the right it was not.
4. Firing Your Knobs
Once you have finished painting the last step is firing your piece. As mentioned in the Introductory blog, if you do not have a kiln many local artists or ceramics shops are willing to fire pieces for free or a minimal fee. These knobs should be fired at Cone 06.