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  • ScottHitchins commented on Coraliev's instructable Pizza Oven Build7 weeks ago
    Pizza Oven Build

    Look closer and you'll realise that thermal mass is actually lacking in the hearth (base of the oven): Over the concrete base is an insulating layer (Vermiculite or perlite can be used but perlite has greater volume for your money. Wear a dust mask when working with either) As any mass outside the insulation doesn't count as thermal mass, you are left with the sand layer and the tiles as TM. Replacing the tiles with solid bricks would probably do the job, particularly if laid on their sides, unmortared. For catering, parties or large families, a much thicker sand bed (~100mm plus) would improve heat storage and therefore cooking time but at the cost of more fuel; so the balance comes down to what you use your oven for. Heat stored in the hearth masonry is vital to getting the base cr...

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    Look closer and you'll realise that thermal mass is actually lacking in the hearth (base of the oven): Over the concrete base is an insulating layer (Vermiculite or perlite can be used but perlite has greater volume for your money. Wear a dust mask when working with either) As any mass outside the insulation doesn't count as thermal mass, you are left with the sand layer and the tiles as TM. Replacing the tiles with solid bricks would probably do the job, particularly if laid on their sides, unmortared. For catering, parties or large families, a much thicker sand bed (~100mm plus) would improve heat storage and therefore cooking time but at the cost of more fuel; so the balance comes down to what you use your oven for. Heat stored in the hearth masonry is vital to getting the base crisp on a pizza before the top burns from radiant heat. The rest of the oven has good thermal mass .

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  • ScottHitchins commented on Coraliev's instructable Pizza Oven Build7 weeks ago
    Pizza Oven Build

    Thermal mass isn't just an efficiency issue: it has a lot to do with the way certain foods should be cooked with bottom heat, heat re-radiated from the roof and the oven's air temperature. Thermal mass is also about heat storage as, apart from pizza, pretty much everything else is best cooked after the fire is removed and the door closed. -mind you, most backyard wood fired ovens almost never get beyond just pizza -because it is incredibly good cooked this way

    Looks great. You would have been better off using bricks for the hearth rather than tiles as this extra thermal mass is useful for getting the pizza base crispy before the top burns. Another addition I would suggest is to either install a well-fitted flue damper or a secondary inner door which sits in past the chimney: While pizzas are cooked with an open door and an active fire, every other type of baking you might like to try involves raking out the coals, sealing the oven and baking / roasting on the stored heat. (see book "THe Bread Builders" for details). You completely correct about not using firebricks / refractory bricks: I've built ten ovens and only one had bricks crack; the one where I used firebricks that happened to be on site

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