I have a old 100lb propane bottle that I cut in half and I am waiting to make it into a propane forge whats everyone's thoughts 

Way too big.

-Can you do it, yes.  Should you do it, no.  Because of the larger diameter you will end up with a gas hog and something too large than what is needed for almost all projects.  The shell is the most basic and cheapest part of a propane forge.  Don't use something too large just because you happen to have it.  You will burn up what you save in additional propane usage very quickly.   I suggest something smaller, e.g. a 20# propane tank.

"By hammer and hand all arts do stand."

What they said.

Double ditto, WAY too large. Save it to hold propane.

Frosty The Lucky.

Dogpile on "too big".  Now why do you think you need one that large?  What do you want to use it for?

 Any forge that large should be a brick pile type. That way, you can reconfigure it after you have paid your fuel bill a time or two.

You can probably buy enough K-26 insulating fire bricks to do it for what enough Kaowool to line a 100lb. propane tank forge would cost. Seeing as you already cut the tank in half disregard my previous suggestion to store propane in it and turn it into a BBQ. 

When I finally got my shop closed in I built what I thought would be a very versatile shop forge. It's roughly 24" square with a lid mounted on a scissor jack so I can lift the lid and arrange the IFBs that partition sections and shape. It's heated by four 3/4" T burners. In the 20 years I've had the thing I've only fired up all 4 burners a couple times. First for pics and to cure the refractory. After that a couple times when I had enough guys over to need room in the forge for 5-6 guy's work. 90% of the time I use that forge I fire a single 5" x 5" x 8-9" section and 3 burners just sit there looking like weird trees.

Frosty The Lucky.

Jerry,

24” square forge?!?

you should at least fire that big dude up an cook a pizza in there once in awhile! 

Yeah, that's the OD subtract 5" for the IFB sidewalls. I could cook pizza in it but it sheds stuff, dust from the ITC-100 on the lid, from scraped IFBs (Insulating Fire Bricks), flux, scale, etc. You  know the usual . . . stuff found in a propane forge. 

Oops, it's only 20" square, posting a pic and it's obvious. This is it when it was new about it's 3rd iteration and pretty much how she is now. The open section closest is my usual when I fire it up, I'll move the partition and light the one in line behind for heating longer sections. 

Frosty The Lucky.

 

Oh well, it could still cook a small pizza! 

as for the stuff it sheds, that’s just extra toppings!

It would be nice if IFI had another permanent section on brick forges, with lots of photos.

If you used a stainless steel peel and moved around you could bake a pizza around 40" Dia. A Medium in Alaska.

You could be right Mike, I'll bet if a VOLUNTEER sifted and organized all the posts and pics of brick forges Glenn or Steve would start a subsection for you.

Frosty The Lucky.