billy larson wrote:I am tearing down an old school built in 1927 and taking down the chimney it has fired red brick one layer on the outside, two layer soft brick, and one layer hard fire brick. do you think 2 layers of soft brick be insulating fire brick or common. I am guessing insulating but is there any way to tell?
Dale Hodgins wrote:
With the dense firebrick, the weight is not what matters, so long as it doesn't conduct heat away from the hot surface so quickly that the quality of the burn is negatively affected. And it doesn't matter how hot the whole brick is during a burn. Only the surface temperature of the portion of the brick which contacts the flame could effect the fire. When a fire first gets to roaring, the surface of bricks near the top of the tunnel may reach 1000F, while 4 inches away, the outer edges of those same bricks haven't yet reached 100 degrees. The fire doesn't know about this. It will only react to the surface that it is exposed to. Delayed heat transference is the reason that we need firebricks which are made from a million little broken bits that are mixed with clay slip and re fired. Temperature shock destroys most rocks and bricks. If the whole mass of a solid object heated up nice and evenly, chimneys could be built from glass blocks. They cannot, because glass is very vulnerable to thermal shock when one portion of a block gets much hotter than another.
Erica Wisner wrote:
2) Both types of brick, and varieties in between, are suitable for use in rocket mass heaters. Almost all clay-based materials are capable of handling over 2000 F.
gus miller wrote:
i still am unclear whether it's safe to use 44 cent home depot red clay bricks for the entire core (feed tube, burn tunnel, riser).
i understand it's preferable to use insulated firebricks for the core but can i safely use these home depot bricks for the core ?
are any/all bricks sold as "clay bricks" ok (albeit not preferable) for construction of the core?