CalSil Board vs MW board/block

[Northup]

in searching for materials locally I have found both CalSil Boards and MW blocks for my hearth insulation.
The CalSil boards are about 50$-60$ more then doing the hearth in the MW block both 2" thick.
1900°F MW Block-19 Insulation 2"x12"x36" - 2000°F Lightweight CalSil board 2"x24"x36"

I did some searching on the forums and found a few post talking about how the Calsil board is a little better for insulation but the MW blocks maybe better at not taking on moisture. Has anyone used both of these or has any more informative comparisons of these two options? Thanks for any input

[UtahBeehiver]

You need to compare several items when looking at insulation, first compressibility of the insulation (something over 90 psi should be good), thermal transfer rating or K. How do you know the MW blocks will absorb less moisture? The only water proof insulation I am aware of is FoamGlas. Is there a spec sheet you can attach?

[Northup]

I don't know that they absorb less moisture, it was something that I read on two different post while searching. Ill try to relocate those post. They didnt provide me with a spec sheet yet on the MW blocks, I am leaning towards the calsil but didnt want to commit until I look at the other possibilities.