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-   -   Type of sand for sand form in cob oven (http://www.fornobravo.com/forum/f43/type-sand-sand-form-cob-oven-19718.html)

valtron 08-02-2013 07:38 AM

Type of sand for sand form in cob oven
 
Hi everyone, I'm almost at the point of ordering sand and clay for building the dome. From what I've read, angular sand is recommended for for the actual dome, but I can't find anything on what to use for the form.

Is angular sand also best for making a sand form that'll stay together, or do I need a smoother, more fine sand? My oven will have a 30" inner diameter.

stonecutter 08-02-2013 08:08 AM

Re: Type of sand for sand form in cob oven
 
Sharp grained aggregate is best for all masonry work.

cobblerdave 08-02-2013 01:10 PM

Re: Type of sand for sand form in cob oven
 
Gudday
Put a small amount of clay in the sand and slightly damp so that it holds its shape for the mold. Include some plastic drink bottles in your mold you'll have less sand to shovel out at the end.
Regards dave

david s 08-02-2013 01:40 PM

Re: Type of sand for sand form in cob oven
 
If you want to get really accurate the ratio is around 10% water. Polystyrene fruit boxes are also good to stack under the sand castle to reduce the amount of sand required. Use a stick, cut to length, of the internal dome height, placed vertically in the centre of your floor.It is pretty easy to get a perfect hemisphere by eye, working from the centre point at the top and down to your perimeter at the base. Use the flat of a trowel to tap the sand into the required form on the outside.


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