Castable with metal needles. Are these correct kind?

[stevef22]

Hi, I found these metal needles here

EBAY

Rolling idea around for castable 36" dome, low vault pizza oven.

Planning on building a sand template and skinning with 3-4" inches of homebrew at
3:1:1:1, { Sand : Fire Clay: Lime Hydrated Type S : Portland }


Is it ok to mix metal needles in this? Is my homebrew ratio correct. Ive seen many say 6:1:1:1 ratio is better. What are your thoughts on this?


Thank you, Steve

[david s]

I can't read what you've got. They should be stainless. They are not essential, but make sure you add the very fine polypropylene fibres that burn out and give you a measure of protection from steam spalling. They are far more essential. Stick to the 3:1:1 brew. It sounds like it's way too rich, but if the cement fails the lime takes over and if that fails the clay takes over. In practice the recipe works well and has been used successfully by many.

[stevef22]

Thank you very much