clay by color

[mudder]

there are different colors of clay around here.  is there a type or color that is more "refractory worthy" than others?  the whiteish yellow clay from my yard turns brick red after being in a fire. it seems to hold up great but wondered if other types/colors mite be better.

[belgiangulch]

I have heard that the blue/grey clay is inferior, whitish/yellow is the color of lincoln 60 ?? so maybe you have the good stuff already. Make test bricks from the different colors and test them, after just drying and after heating and then report back here with pictures and your results.

[Deleted]

Firing colors:

red: iron
yellow: titanium
black and brown: manganese
gray to anthracite: Chrome

Does not tell much about "refractory worthy".

Iron may lower the melting point to around 1400°C /2552 °F
Sodium or potassium may lower the melting point to around 1000°C /1832 °F,
without a hint by color.

[mudder]

i built a cast 4" rocket outside the year before last. i used sand perilite and my yellowish white clay, from my yard. it seemed to hold up great to the heat. was still in great shape(even out in the rain and snow of 2 indiana winters!) till a tree limb crushed it this spring. the first 2" from the core were red colored and hard like bricks. so i know that stuff is fine but just wondered if it could be improved upon by other clays. the one i build this summer will utilize the kiln blocks i acquired for the burn chamber and tunnel. then a cast riser from the same clay mixture as the first.

thanks for the insight given guys. rocket on!