[TheForge] Strengthening castable refractory

[Marc Godbout]

I received some technical info from Mt. Savage on the Delta t Crete 25
insulating castable I'm about to use. In case anyone's interested here
are a couple of the specs:
Density after drying:	54 lbs/ cu.ft.
Max service temp:	2500 degF
Therm conductivity:	1.4 BTU/Sq.Ft./Hr/degF/in. at 500 degF
			1.9 at 1500 degF
			2.3 at 2000 degF.
Water for casting:	Approx. 55% by weight

Now a question. The best way to prevent checking is to use the minimal
amount of water. They give an approximate amount, 55%, but how do I tell
when it's enough? From what I've read on other mixes, it should be just
enough to hold it together when clumping it in your hand. Does that
sound right?

My local refractory place has SS needles for $18 / 2 lb bag. Sounds a
little expensive, but not too expensive.

Hopefully I'll get to casting this weekend. The shell is just about
done.

-- 
Marc Godbout
http://www.ironringforge.com

New England Blacksmiths Membership Director
http://www.newenglandblacksmiths.org