Arch insulation?

[Machinist67]

Looking at using vermiculite or clay kitty litter in my arch.
What are the pros and cons to each?x

[Scribner's Mountain Maple]

Vermiculite is light, clay is heavy. That's all I got. But is why I use Vermiculite.

Ben

[Flat Rock Farmers]

I'd say go with vermiculite. The clay kitty litter would absorb moisture from any rain and such from your stack when you're not boiling
as well as from summer humidity in the off season. That moisture could eventually rust out your arch where ever you use it. At least
that's what I was told before I bricked and insulated my arch.

Jay