Jeffrey Landis wrote at 2013-01-11 12:01:49
As an artist, myself who is forever tying to find ways to replicate a technique I admire without the actual expense or work/talent required, (a.k.a. "the hard way"), I believe the questioner is attempting to achieve the effect of crackled porcelain on a concrete form.
I actually bought a vase like that at a discount pottery and textiles place here in Ohio that is exactly that. Virtually everything sold in this particular place are close-outs from places like Pier One most comes from India whose peoples are masters at creating things that look old.
Unless you are planning to develop a process to produce many pieces, you might just visit the craft center or paint store and purchase some crackle medium. There are many brands and you can get a wide range of effects simply by how you apply it. They can be used with any type of paint (indoor, outdoor, enamel, latex, etc.)
They are easiest to apply to a smooth surface, but a little experimenting may yield some interesting looks.
If you use outdoor paint intended for masonry and still have concerns about it lasting, you can over-coat it with some clear masonry sealer.
A nice plus, is that if you don't like it, you can paint over it. You can't do that with ceramic glaze.
Keep in mind that concrete is naturally porous and the vase I have is purely decorative, as the water seeps through from inside. So it would be a good idea to seal it with a couple coats of concrete driveway sealer anyway, if it's going to be exposed to the elements.
Another idea would be to apply a heavy epoxy resin to the areas you want to "GLAZE" to create a smoother and impervious surface to paint on. Epoxies are clear and tintable, so you could achieve the look of a heavy base glaze with it.
With that said, It IS possible to apply or bond ceramic glazes to masonry. The vase I have is very heavy, thick walled concrete with a substantial layer of white porcelain covering 3/4 of the exterior and red glazed decoration on top of that.
But it may prove expensive and complicated with no guarantee of a predictable result.
As the answerer indicated, however, it is likely a process requiring high heat (1100º F) and sophisticated (or at least, large) kilns.
This effect was perfected by the Chinese (See RU WARE) DURING THE SONG DYNASTY and replicating the process has been attempted by potteries around the world with varying levels of success ever since. Some of these attempts, however, have yielded new styles (see RAKU).
These techniques take a lifetime to master and ARE VERY DANGEROUS!
In the early days of pottery making, CRACKLED GLAZE was considered a flaw. It happens when the pots are cooled too quickly, just as ice cubes crack when dropped in a warm glass of lemonade. The glaze cracks-not the pot-since it cools much faster than the clay.
Chinese potters saw the beauty of this reaction on glazes and learned to control and force it by REMOVING THE POTTERY WHILE STILL HOT DIRECTLY FROM THE KILN.
THEY ALSO LEARNED THAT BY PLACING THEM IN A COMBUSTIBLE MATERIAL SUCH AS STRAW, ANIMAL HAIR OR WOOD SHAVINGS THE OXIDIZATION OF THE VARIOUS MATERIALS IGNITING CAUSED A DESIRABLE AND SPONTANEOUS PERMANENT DISTORTION OF COLOR.
Modern technologies have made the process safer, but much more expensive and complex with the development of THE REDUCTION KILN.
However, the old method still is practiced and preferred by many potters around the world.
Hope that helps.