Saggar firing is extremely unpredictable, but here are a few additives that can favor bright colors: Salt You can just throw some rocjk salt in the saggar, or you can get fancier and soak some absorbent materials, like strips of burlap, in a strong brine and let them dry, then wrap these on the pot. Miracle-Gro Sprinkle it in the saggar, or use sprinkle it on a banana peel and wrap that on the pot. Copper sulfate (Sold as a swimming pool additive at hardware stores) Again, sprinkle in the saggar or use something to hold it against the pot. Yields reds and (sometimes) greens. Ferric chloride (Sold as PCB etchant at Radio Shack) spray or brush onto pot before firing (it’s corrosive, so be careful). Favors oranges and pinks. Steel wool Used sparsely gives some nice reddish browns.