Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the wall
to increase the heat capacity - I thought by adding at least one course of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in use,
the outer wall of the oven gets too hot to touch for more than an instant -
I would guess about 100-140C.
Any advice appreciated.
Andy

"Andy Phillips" wrote in
:

Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the
walls are not thick enough to retain much heat - therefore, having
heated the oven with a wood fire and raked it out, it's only possible
to cook about two pizzas before it's cooled down. I'd like to be able
to cook at least four pizzas and maybe some bread afterwards. I
therefore need to thicken the wall to increase the heat capacity - I
thought by adding at least one course of bricks around the sides and
top of the oven, followed by an inch or so of render. Question is, do
I need to use special heat-proof bricks (eg firebricks) and cement, or
can I get away with normal house bricks and mortar? I'm concerned
that the mortar and render will crack - when in use, the outer wall of
the oven gets too hot to touch for more than an instant - I would
guess about 100-140C. Any advice appreciated.
Andy




Andy,

Did you build the oven or did a professional oven builder/mason build
it?

If you had a professional or mason build it, you should ask him. It
would seem to me that having an exterior surface that is oven 100C is
not a good thing and should be covered by guarantee.

If you built it, then check your instructions to see if you maybe left
out something. If you followed the instructions to the letter, get in
touch with the people who provided the instructions.

I'd also worry about to the very short cooking time. This indicates to
me that you don't have near the thermal mass you should have.

My experience with industrial annealing ovens was that they didn't
transfer too much heat to the outer surface and they took a long time to
cool down for maintenance, but it's been 40 years, so I might be a
little foggy on the fine points. g

Barry

Andy Phillips wrote:
Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the wall
to increase the heat capacity - I thought by adding at least one course of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in use,
the outer wall of the oven gets too hot to touch for more than an instant -
I would guess about 100-140C.
Any advice appreciated.
Andy



Andy,

First, Barry should have followed your link. It appears you bought a
commercial product. However, what we call "the implied warranty of
merchantability and fitness for use" in the US may be a legal concept
that does not have an exact equivalent in the UK. In any case, this
looks to be the product of a home-based microbusiness, so there wouldn't
be much point in pursuing a remedy with them.

So, second, let's look at your proposed solution.

What I've seen done to good effect is to design in a gap between the
inner shell (which you own) and the outer shell (which you propose to
construct) and to fill that gap with vermiculite insulating fill.
Vermiculite got a bad rap because the principal source of it in the US
was laced with asbestos. For all I know, all sources of it are laced
with asbestos. So you will want to be careful handling it (gloves, long
sleeves, respirator), and you do want to ensure that the space you are
filling is then sealed in an airtight fashion with some sort of
inspection plug at the top where you can add more vermiculite if it
settles over time.

This insulating layer cuts down significantly on the overall weight of
the oven (a possible concern depending on what it's sitting on) as well
as on material costs.

The outer layer can be ferrocement, and you can skip the bricks altogether.

Or you can do it your way, of course. I'd suggest firebrick, as it's
lighter in weight and therefore easier on your back as you do the work.
Of course it may also be harder to come by, in which case I'd suggest
chimney brick (solid clay brick, as opposed to the sort with holes in it
that is used for walls).

Good luck!

Dick

In article ,
"Andy Phillips" wrote:

Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the wall
to increase the heat capacity - I thought by adding at least one course of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in use,
the outer wall of the oven gets too hot to touch for more than an instant -
I would guess about 100-140C.
Any advice appreciated.
Andy



They suggest you can leave the fire on and cook with it that way. This
is actually what is done in all Neapolitan pizza ovens anyway (live fire
cooking). That would be the easiest thing to try first.

See the Forno Bravo site for exhaustive discussion on all aspects of
wood fired ovens. See for example

http://www.fornobravo.com/pizza_oven...en_firing.html

and go to their forums

http://www.fornobravo.com/forum/

Roland

The oven is a pre-fabricated modular design made of refractory cement - it
simply slots together. I agree with Barry that it doesn't have enough
thermal mass - but I guess this may be unavoidable considering the design,
as thicker materials would be too heavy to lift.
As Roland says, the manufacturers suggest keeping the fire running while
cooking the pizzas - the problem is the small size of the oven, which
prevents me from moving the fire away a sufficient distance from the pizza
to prevent that latter from burning. My ideal solution would be to build a
custom oven on a larger scale, but I just don't have the space.
I'd considered Dick's suggestion of making a separate outer wall and
filling the gap with vermiculite, for the reasons he gives in his posting -
provides insulation between the inner and outer walls and doesn't add too
much weight. I had rejected this because I couldn't figure out how to keep
it watertight, ie how to cap it - my diy skills are limited. But your post
has convinced me to take another look at this option.
Cheers
Andy


"Joe Doe" wrote in message
...
In article ,
"Andy Phillips" wrote:

Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the
walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about
two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the
wall
to increase the heat capacity - I thought by adding at least one course
of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in
use,
the outer wall of the oven gets too hot to touch for more than an
instant -
I would guess about 100-140C.
Any advice appreciated.
Andy



They suggest you can leave the fire on and cook with it that way. This
is actually what is done in all Neapolitan pizza ovens anyway (live fire
cooking). That would be the easiest thing to try first.

See the Forno Bravo site for exhaustive discussion on all aspects of
wood fired ovens. See for example

http://www.fornobravo.com/pizza_oven...en_firing.html

and go to their forums

http://www.fornobravo.com/forum/

Roland

Dick Margulis wrote in
:

Andy Phillips wrote:
Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the
walls are not thick enough to retain much heat - therefore, having
heated the oven with a wood fire and raked it out, it's only possible
to cook about two pizzas before it's cooled down. I'd like to be able
to cook at least four pizzas and maybe some bread afterwards. I
therefore need to thicken the wall to increase the heat capacity - I
thought by adding at least one course of bricks around the sides and
top of the oven, followed by an inch or so of render. Question is, do
I need to use special heat-proof bricks (eg firebricks) and cement,
or can I get away with normal house bricks and mortar? I'm concerned
that the mortar and render will crack - when in use, the outer wall
of the oven gets too hot to touch for more than an instant - I would
guess about 100-140C. Any advice appreciated.
Andy



Andy,

First, Barry should have followed your link. It appears you bought a
commercial product. However, what we call "the implied warranty of
merchantability and fitness for use" in the US may be a legal concept
that does not have an exact equivalent in the UK. In any case, this
looks to be the product of a home-based microbusiness, so there
wouldn't be much point in pursuing a remedy with them.

So, second, let's look at your proposed solution.

What I've seen done to good effect is to design in a gap between the
inner shell (which you own) and the outer shell (which you propose to
construct) and to fill that gap with vermiculite insulating fill.
Vermiculite got a bad rap because the principal source of it in the US
was laced with asbestos. For all I know, all sources of it are laced
with asbestos. So you will want to be careful handling it (gloves,
long sleeves, respirator), and you do want to ensure that the space
you are filling is then sealed in an airtight fashion with some sort
of inspection plug at the top where you can add more vermiculite if it
settles over time.

This insulating layer cuts down significantly on the overall weight of
the oven (a possible concern depending on what it's sitting on) as
well as on material costs.

The outer layer can be ferrocement, and you can skip the bricks
altogether.

Or you can do it your way, of course. I'd suggest firebrick, as it's
lighter in weight and therefore easier on your back as you do the
work. Of course it may also be harder to come by, in which case I'd
suggest chimney brick (solid clay brick, as opposed to the sort with
holes in it that is used for walls).

Good luck!

Dick


Dick,

The asbestos vermiculite was primarily mined in Libby, Montana. The
book about that disaster laid it all out fairly well. There weere
several sources of vermiculite in the US and Canada. The EPA in the US
and the Canadian Health Ministry (I think that's the name) forced Libby
and all other asbestos vermiculite off the market in the verey early
1990s.

I would be very surprised if any vermiculite on the market today,
especially in Europe, had asbestos in it.

On other subjects,

Keeping the water out between uses is simple, get a tarp.

As for insulation, you could get bats of fiberglass and make a box to
put over the top of the oven while it's heating. It'll look like hell,
but it'll work and will do until something better comes along.

Keeping the oven heating is a good option.

If things get too intense, just slide a sheet of metal under the pizzas
and you'll slow down the burning -- although some of us like a slightly
charred pizza.

Barry

Barry Harmon wrote:

Dick,

The asbestos vermiculite was primarily mined in Libby, Montana. The
book about that disaster laid it all out fairly well. There weere
several sources of vermiculite in the US and Canada. The EPA in the US
and the Canadian Health Ministry (I think that's the name) forced Libby
and all other asbestos vermiculite off the market in the verey early
1990s.

I was aware of only the broad outline, involving Libby and W.R. Grace.



I would be very surprised if any vermiculite on the market today,
especially in Europe, had asbestos in it.


I would be, too. But better safe than sorry. I don't know anything about
geology, and whether some vermiculite sources are totally asbestos-free
or just "low enough" in asbestos is outside my ken.

On other subjects,

Keeping the water out between uses is simple, get a tarp.

As for insulation, you could get bats of fiberglass and make a box to
put over the top of the oven while it's heating. It'll look like hell,
but it'll work and will do until something better comes along.

What temperature does fiberglass melt at (just asking)?

Dick Margulis wrote:


What temperature does fiberglass melt at (just asking)?

It's pretty good to over 1000C, and really starts to degrade above 2000C.

Dave

Dick Margulis wrote in news:135jcbdin74t465
@news.supernews.com:


I was aware of only the broad outline, involving Libby and W.R.
GraceLESS. :-(

Note change.

Barry

Andy, I've good luck with 3M's Nextel fabrics for some work related
applications. They are essentially like Thinsulate fibers but made
with ceramics. They are very pliable and easily
shaped/folded/stacked, etc. Here's some info:

http://tinyurl.com/2wutkh

I can't direct you to a source (I work in another area of 3M and get
it internally). It helps keep the space shuttle insulated so it would
likely work for your pizza oven! NASCAR teams also use it as
insulating barriers between hot exhausts and the cockpits for driver
comfort, too. I mention this as it might be available through racing
supply catalogs and sources.

http://tinyurl.com/2twawp

http://tinyurl.com/3223z6



On Sat, 26 May 2007 23:00:04 +0100, "Andy Phillips"
wrote:

Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the wall
to increase the heat capacity - I thought by adding at least one course of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in use,
the outer wall of the oven gets too hot to touch for more than an instant -
I would guess about 100-140C.
Any advice appreciated.
Andy


Craig Schroeder
craig nospam craigschroeder com

Craig,

Cool idea - this got me thinking about whether my aim was to insulate the
inner core of the oven to minimize heat loss, or to increase the thermal
mass also. Most pizza oven rely on the latter strategy and therefore an
outer skin of bricks would be the best option. However, I could try an
insulating blanket first. I'll try your links and see what I can find -
doesn't sound the cheapest option though!

Cheers

Andy



"Craig Schroeder" wrote in message
...
Andy, I've good luck with 3M's Nextel fabrics for some work related
applications. They are essentially like Thinsulate fibers but made
with ceramics. They are very pliable and easily
shaped/folded/stacked, etc. Here's some info:

http://tinyurl.com/2wutkh

I can't direct you to a source (I work in another area of 3M and get
it internally). It helps keep the space shuttle insulated so it would
likely work for your pizza oven! NASCAR teams also use it as
insulating barriers between hot exhausts and the cockpits for driver
comfort, too. I mention this as it might be available through racing
supply catalogs and sources.

http://tinyurl.com/2twawp

http://tinyurl.com/3223z6



On Sat, 26 May 2007 23:00:04 +0100, "Andy Phillips"
wrote:

Hi,
I have a pizza oven made from refractory cement (see
http://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about
two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the
wall
to increase the heat capacity - I thought by adding at least one course of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in use,
the outer wall of the oven gets too hot to touch for more than an
instant -
I would guess about 100-140C.
Any advice appreciated.
Andy


Craig Schroeder
craig nospam craigschroeder com

On May 26, 3:00?pm, "Andy Phillips" wrote:
Hi,
I have a pizza oven made from refractory cement (seehttp://www.purimachos.demon.co.uk/pizza.htm). This works OK, but the walls
are not thick enough to retain much heat - therefore, having heated the
oven with a wood fire and raked it out, it's only possible to cook about two
pizzas before it's cooled down. I'd like to be able to cook at least four
pizzas and maybe some bread afterwards. I therefore need to thicken the wall
to increase the heat capacity - I thought by adding at least one course of
bricks around the sides and top of the oven, followed by an inch or so of
render. Question is, do I need to use special heat-proof bricks (eg
firebricks) and cement, or can I get away with normal house bricks and
mortar? I'm concerned that the mortar and render will crack - when in use,
the outer wall of the oven gets too hot to touch for more than an instant -
I would guess about 100-140C.
Any advice appreciated.
Andy

Andy, What a cute oven. I amde a adobe oven from the sunset adobe
oven plans, but mine is not true to the ploans but close. I use mine
quite a bit. It is permenent in the garden outside the house door.

But to your situation. I think I would wall up the stand with
playwood and fillit with sand. great theraml mass. Then I would
stretch some chicken wire or hardware cloth over the whole thing,
except place of the chimmney, and cover the hwole thing with 2-3
inches of concret, mud and straw mixture. Mine has more mud and
concrete in it. During hard winters you might get some cracks but
they can be filled with concrete eaily to remedy that. Mine
definately is not as cute as yours but man does it hold heat and I can
do pizzas, then a big beef roast and 10lb of potatos after. Check out
the sunset article as a place to start. I can email you a photo of
mne if you like. It is nothing fancy simply functional. I am
thinking of covering it with broken dishes and pttery next time I have
cracks to repair. PaM