Hi Rob, I spent twentyfive years making highfired stoneware and porcelain, my kilns fired 1250-1320 centigrade. 1000F will 'just about' fire soft terracotta garden pots!Only the lowest melting RAKU glazes and Egyptian paste will melt at 900-1000 farenheit. You may be confusing farenheit and centigrade. Most pottery kilns will easily fire over 1150 centigrade, (high fired earthenware temps) The soft firebrick used in the forges is ideal and works as you know, be careful of kaowool once it is heated it will shed ultra fine fibres especially if you bump it or have a strong airflow. This is VERY BAD STUFF to get into your lungs or eyes, silicosis and a grim death eventually. You can paint it with a ceramic slurry to stabilise it and I would recommend you do. If you want to check, shine a bright light across forge with a dark background ( eg at night )you will see millions of tiny bright fibres floating about.
I once took part in a big craft/art fair and had lots of fun with the ironwork and glass guys, we collaborated and built a glass lehr using combined skills and materials. It worked a treat and they 'taught' me to blow glass! The Danish glassblowers told me I was making 'Viking glass'. A polite way to say it was ok if crude!!
chrisg