The clay is somewhat softer at ^06 than at ^04. It will typically absorb a little more glaze, be a bit more fragile and scratch easier. Most low-fire loads are bisqued at ^04 and then glazed at ^06. For mid-range (^5/^6) or high fire (^9/^10) it probably doesn't make much difference.
However, for low fire pieces you always want your bisque to be at least one cone hotter than your glaze. So if you're glazing to ^06 you should probably refire that load to at least ^05 before you glaze-fire it.
I am firing glaze to ^6. I always thought it was the norm to bisque at 04. Than when I started seeing people say they fire to 06, I was wondering what the difference was. So now that I have fired to 06, do I put the glaze on thicker? Will it affect the color?
Nope and nope! Just be a teeny bit more careful handling your pieces when you're dealing with handles or glazing the insides, because I have found that attachments are just slightly less secure, and large pieces with glaze on the inside are a little more fragile when they get wet. It's really hardly noticeable. If you're mid- or high-firing, anything between 06 and 02 is fine. I've done them all at various times.
Thanks. Most of what I'm doing is flat tiles. The other thing is a tunnel to put in my aquarium. Great to know I can use lower temp cones to bisque.
Another question, I'm doing an orange car and trying to figure out what would be a good background color. Don't really want to do black, the whole Halloween colors. The orange is a bright orange. Any suggestions would be greatly appreciated !!