I use liquid clay but not straight out of the bottle. I'm concerned that the translucent quality of the liquid clay would show as fine lines that don't match in color. what I started doing was to take a small little bit of the same color clay that's in the area of the crack. Put a couple drops of kato poly clay liquid and mix it. I use a small paddle tool. It looks very similar to that little dental mirror the dentist sticks in your mouth only really tiny. But any firm tool would work. I mash the liq clay and the colored clay over and over until well mixed. It should be soft like paste or pudding. Scoop some on your tool and press into the crack. Keep doing this until the crack is completely full. Then smooth over the surface and re-bake. After baking, the crack is no longer noticeable.
If the crack is large enough, try well conditioned clay of the same color straight without the liquid clay added. Smooth the surface around the edges of the crack with your fingers or a soft bristled paint brush.
If the crack is really fine, too fine for the first method thin out the mix with a little more liquid clay.
The great thing about any of the above methods is that you are always using the same color as the surrounding clay which really helps disguise the crack entirely.
