Author Topic: Pizza Science - Heat Conductors and Insulators  (Read 4610 times)

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Offline jerrym

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Pizza Science - Heat Conductors and Insulators
« on: November 14, 2010, 05:29:38 AM »
since joining the site have switched from warm to cold fermentation and  stopped using rolling pin to stretch the dough step change achieved - many thanks to all the top notch posts making this possible.

in trying out the new dough and methods i found the pizza base was getting too crisp before being cooked (using pan). Consequently re tried the various other "trays" that i have with following results:

1)   Steel pan too crispy base/top rim, top centre not fully cooked
2)   Steel perforated screen far too crispy base over the perforation holes, top centre over cooked
3)   Aluminum plate soft base/top rim, top centre fully cooked
4)   Stainless mesh/screen crispy base and top rim, almost fully cooked

i have domestic electric oven 500F and 9 min bake

all of the above are high conductors of heat. Results suggest I should 2 stage cook ie aluminum plate then mesh screen.

I picked up from the site that a stone is the best option yet stone is a low conductor and effectively opposite to the trays.

is there any existing info to gain a basic understanding of the science of making pizza ie why the stone works so well.



Offline Jet_deck

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #1 on: November 14, 2010, 07:53:11 AM »
Most all of my pizzas cook differently, depending on the hydration, protein content of the flour and the inclusion of sugar/oil.  It might be very well worth your time to put up your recipe that you cook most often.  Then one could make suggestions as to the benefits of using a stone alone or in conjuntion with one of the pans that you have.

To answer your question, there is some good reading and reference here :http://www.pizzamaking.com/forum/index.php/topic,10072.0.html


Her mind is Tiffany-twisted, she got the Mercedes bends

scott123

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #2 on: November 14, 2010, 07:08:07 PM »
Jerry, if one were to form a pizza, put it on a room temp stone and then put the stone in the oven, the poor conductivity would cause it to take forever to cook.  Preheating the stone, though, changes the playing field.  Instead of the distant (ie inefficient) bottom electric element or gas flame baking the bottom of the pizza (through the middleman of the metal pan), the heat source is the stone.  Well, that is, if it's a good thick stone that can store a lot of heat.

There's a lot of tricks to shortening baking times with pans (such as using black colored, heat absorbing pans, putting the pans as close to the heat source as possible and/or working with a red hot/maximum radiation element), but, unless you have a freakishly high watt/btu bottom burner, you'll never hit the kind of short baking times you'll see with a good stone.  And short baking times are the key to great oven spring/great pizza.
« Last Edit: November 21, 2010, 10:58:30 AM by scott123 »

Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #3 on: November 15, 2010, 11:16:36 AM »
thanks for replies. will read up on Jet_deck's link.

the idea of a "heat mass" sits well with me. i have a scrap piece of granite (12mm thk) that i'll try out to see if i can get benefit from my domestic oven (appreciate granite is not a permanent solution down to cracking if liquid spillage occurs).

i'll get a peel and bigger screen on order.

recipe is based on the Jeff Varasano website and his manual kneading method:

plain flour (100%)
water (65%)
sea salt (1.2%)
ADL yeast (0.3%)
thickness factor 0.085

cold fermenting min 3 days max 5 days - have attached pic of dough box at 5 days.

oven is direct electric and quite shallow at 7 inch high. i've moved the thermocouple lower and it hits 500F. i am pretty sure in oven mode only the bottom element works ie the top broiler element is off.


scott123

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #4 on: November 16, 2010, 12:56:03 PM »
Jerry, granite should never go near an oven.  It's high in silica making it structurally very similar to glass.  Glass is, as you're aware, very thermally weak.  We're not just talking about cracking if a spill occurs, we're talking about cracking (or worse) when you open the oven door and the cooler air hits it. Best case scenario is that it will crack after one or two uses.  It's not all that likely, but the worst case scenario is that it will crack violently. Avoid granite as a baking stone at all costs.

Your recipe looks spot on, but the dough looks extremely overfermented.  Are you using warm water?  Is some of that fermentation time at room temp?

If you're using cool-ish water and cold fermenting for the entire run, I might like take a look at your flour.  Weaker flours break down faster. Getting strong flour in the UK isn't an easy task, but other members have done it. I'd talk to Paul (PaulsPizza).

Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #5 on: November 16, 2010, 02:01:17 PM »
scott123,

your quite right on the granite - i use it now and again in trade and it's very brittle in tension (i've broken quite a bit - hence the scrap piece). i'm trying to find proper kiln stone locally to warrington UK. i had picked up from esoog of a place in stoke but i'm not passing for a while - hence the thought of trying the scrap granite as an interim only.

i'm novice on the cold ferment and still learning. so far i've had the lids pushing off after 12 hrs and now at the other extreme with the dough boxes looking dead after 24hrs.

i thinking the same as you suggest - temp of water (had thought of too much manual kneading but feel i can rule this out - hardly kneading it at all and any inconsistency across batches is unlikely to be significant).

for the 1st few batches i was using tepid hand hot water. on the last batch i used straight out the tap. i am pretty sure the flour is fine. i've also gradually reduced yeast down from 0.6% to 0.3% on latest batch. all fermentation is done in fridge. initially i did leave them out for 0.5hr before putting in the fridge but i put straight in the fridge now. i'll crack it - just takes a bit of getting used too.

i'm not really sure what overfermented looks like - it had not dropped whilst in the fridge. the stretching around the perimeter was down to me tilting the box.
 

Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #6 on: November 21, 2010, 09:02:00 AM »
the scrap granite was too big for the oven and decided to try out some 11mm thk roof tiles as a 1st go. i cut a piece of hardboard for a peel.

as this was my 1st time using a peel it was very clear that i need to build skill and technique. i did feel more confident towards the end of the cooking - realising how important (the site's tip) to "shake" the peel often during loading to keep it free.

even so i found it near impossible to stop the wet dough sticking to the peel - i think down to wet dough coming into contact with the peel during the shaping/stretching.

i'm following the jeff varasano manual knead method which produces a "wet" dough at the end of manual kneading which remains unchanged through the cold fermentation.

in the past when i've used the warm ferment i find that by manual kneading the "wet" dough actually become less sticky during kneading even though the hydration is not really changing (added bench flour not significant).

the question is should i do more kneading to reduce the stickiness before the cold ferment or reduce the hydration (from 65%) or just use more bench floor during shaping and work at practicing with the peel loading - in short can loading wet dough on a peel be mastered.


PaulsPizza

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #7 on: November 25, 2010, 08:53:08 AM »
Jerry, granite should never go near an oven.  It's high in silica making it structurally very similar to glass.  Glass is, as you're aware, very thermally weak.  We're not just talking about cracking if a spill occurs, we're talking about cracking (or worse) when you open the oven door and the cooler air hits it. Best case scenario is that it will crack after one or two uses.  It's not all that likely, but the worst case scenario is that it will crack violently. Avoid granite as a baking stone at all costs.

Your recipe looks spot on, but the dough looks extremely overfermented.  Are you using warm water?  Is some of that fermentation time at room temp?

If you're using cool-ish water and cold fermenting for the entire run, I might like take a look at your flour.  Weaker flours break down faster. Getting strong flour in the UK isn't an easy task, but other members have done it. I'd talk to Paul (PaulsPizza).

Sorry Jerry and Scott, I have only just seen this thread..
Jerry,

You can get your hands on some good strong flour from 2 supermarkets here in England:
http://www.mysupermarket.co.uk/sainsburys-price-comparison/Flour/Sainsburys_Taste_the_Difference_Very_Strong_Canadian_Bread_Flour_1Kg.html

and here is the Waitrose flour:

http://www.ocado.com/webshop/product/Very-Strong-Canadian-White-Flour-Waitrose/10827011

I have used both of them and can tell you that they are both good flours. I have used the Waitrose flour more because I just think it is closer to the commercial flour that I use, but I am sure you will make great pizza with either.

Paul

Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #8 on: November 25, 2010, 09:55:06 AM »
PaulsPizza,

very useful to know of the sainsbury's flour - i will have a look for it and give it a try out of interest (as it's a strong bread flour).

i currently use plain floor (at the moment sainsbury's basics plain flour otherwise asda's).

prior to adopting the cold ferment i tried a side by side comparison with McDougalls 00 grade premium plain flour. there was no difference other than the 00 flour is less sticky for a given hydration.

will let you know how i get on.

Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #9 on: November 28, 2010, 06:27:53 AM »
on the last batch of dough i replaced the last 2 stages of jeff varasano's manual knead with a hard manual knead for ~2.5mins each stage. this was enough to just remove the "sticky to the touch" surface of the dough.the fermentation window of the dough seemed to be reduced though.

the "firmer" dough performed very well on the peel and 3 off were transferred to the oven successfully.

need to get the photo's better but they give a sort of indication.

the thin 11m thk "roof tiles" seem to be working a treat as well as the ad hoc hardboard peel.

i intend to work on a few dough options next (type of flour and hydration).

i have to hand some thick 25mm (1 inch) quarry tiles that i will try out next to assess any improvement from a larger "heat mass".


Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #10 on: December 05, 2010, 05:34:58 AM »
i have to hand some thick 25mm (1 inch) quarry tiles - to assess any improvement from a larger "heat mass".
scott123,

many many thanks for that little bit of extra inspiration earlier on in the post.

delighted with the result of the quarry tiles - i am now sorted on this area.

i also used a small piece of roof tile to shelter the thermocouple (RH corner). the oven temperature increased as a result from 500F to 550F. bake time is now 6 mins (was 7/8).

the larger heat mass caused a longer oven warm up ~ 1.25 hrs (c/w ~30mins). the operating temperature range was much better with the heat never dropping below 500F.

these mods delivered a step change in the pizza. many thanks to all members for their help - much appreciated.

Offline jerrym

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Re: Pizza Science - Heat Conductors and Insulators
« Reply #11 on: December 22, 2010, 04:22:23 AM »
almighty disaster - i moved the quarry tiles to rest on the base of the oven. burnt base and under cooked top.

with the tiles on the rack in the lowest position ie the original setup there is an air gap of ~40mm between the steel plate bottom of the oven and the rack. i was interested if improved performance could be gained by placing the quarry tiles directly on this steel plate.

clearly not a good idea. the top and bottom heat distribution came well out of balance

ps for info the heat distribution of the oven has always been out with too much bottom heat. the introduction of the tiles at the 1st shelf position had fixed this.


 

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