So my cast iron forge pan gets reddish to high orange when I've got a big fire (like for welding) going? Would you all recommend claying it, or if I am careful can I go without clay? Would rammed pottery clay work?  Here's a couple pictures--the color balance is a little off as far as the color of the metal--it didn't get yellow. first picture with flash, 2 and 3 without

I would, any clay you can source should work.

There are a number of mixtures, of clay and sand and fired brick dust etc. on this site for claying a forge.  Will it hurt no.  The heat shown will happen anyway, The main reason to clay is to lessen the thermal shock the casting experiences.  I had a new firepot that was cast iron and never worried about it.

Okay, so the firepot isn't terribly close to burning up when it gets that hot? that is good to know. thanks for your help

If it's cast iron, clay it. Any clay will do. Clay from the backyard is better than nothing. Avoid too much water in the mix, it get's trapped between the clay and the forge and causes rust.

well terracotta clay can boil at smithing temps; but I always used what was in the creek or was used by locals for adobe.

Georgia red here, some sand added. Dug a trench to put electric out to my shed, and there's a nasty clay bed about 14" down by the house.  Took twice as long to go through as the last 15' as the rest of the dang trench. Saved some for later.

 I clayed my riveting forge years ago with clay from a dam on my farm, nothing special. I did let it dry for a few days, then started a small fire and heated it initially pretty slowly, then filled any cracks with more clay. It has worked fine.  In answer to your question, yes please clay it before it burns out the joints. 

 

Cheers 

 

Heelerau