Author Topic: Home made electric twin deck  (Read 4730 times)

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Offline crosbie

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Home made electric twin deck
« on: November 13, 2011, 06:52:03 PM »
I'm intending to make a twin deck pizza oven out of kiln stones and a couple of 1500w elements. Each deck is about 450x630x150cm.

I reckon I should be able to get it up to 500C (930F) in about an hour or so.

Does this sound plausible?

 :chef:


Offline scott123

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Re: Home made electric twin deck
« Reply #1 on: November 13, 2011, 10:06:10 PM »
Crosbie, in a perfect world, this is the ideal electric deck oven for NY style (3 minute bake time and above) pizza:

http://www.bakerspride.com/specs/SDECK-5736-01-07.pdf

As you can see, it's 12 kilowatt.  The wattage dictates the rate at which the stone pre-heats, so if you've got a really thick stone and a couple hours for pre-heating, you should be able to get one or two good pizzas out of a 3000 watt oven, but don't expect a lot of pizzas at one time, because, once the stone has given off some it's heat, it's going to take a while to replenish it.

The G3 Ferrari oven is 1200 watts

http://www.pizzamaking.com/forum/index.php?topic=9486.0

but that's not a deck oven.

If you're going to build a 3000 watt oven, though, I would work along these lines- minimal vertical space (perhaps with a hinged top) and only enough interior space for one pizza.

And this is assuming you have access to very inexpensive oven building materials.  If you're going to be spending more than about 150 euros, you might as well start looking for G3 ovens or their clones (deni pizza bella).  Unfortunately, the G3s make small pizzas, but, for the price, that's about the best you can do.

A 3000 watt DIY pizza oven might be feasible, but I think a lot hinges on the elements you're working with.  Do you have a photo?
« Last Edit: November 13, 2011, 10:29:18 PM by scott123 »

Offline crosbie

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Re: Home made electric twin deck
« Reply #2 on: November 14, 2011, 03:44:46 AM »
Scott123, the oven is intended only for the hungry family (with occasional pizza party) as opposed to a commercial production line. And it's for the likes of those who just want to press a button as opposed to light and tend to a fire. Sacrilege, perhaps.  >:D

I'm thinking that if I surround a space with 3" kiln stones, and then 1" or so of insulation about that, then 1.5kW might just be enough to replenish after the door's been opened to put a cold pizza in. I'm intending to use a 1.5kW element such as is found in the Lincat PO49 for one deck, and a ceramic 1.4kW radiant element for the deck underneath, e.g. http://www.ceramicx.com/en/lffe-large-full-flat-element - directed from the rear wall of the deck to simulate a fire.  :-[  I'm also interested in seeing what the difference might be.

I'll let the dimensions be determined by the building materials (bricks & elements), i.e. each deck is 614x458x114cm (my previous size was from memory). That's good for 4 medium pizzas or 2 large ones.

I appreciate that I am unlikely to end up with a cost effective solution, more a luxury one. I'm just hoping it might actually be able to cook pizzas properly.

Offline scott123

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Re: Home made electric twin deck
« Reply #3 on: November 14, 2011, 06:08:08 AM »
Crosbie, if you have 3" of kiln stones on all sides, with those elements, it will take quite a few hours for the oven to reach a suitable temp for pizza.  Very thick stones act like sponges.  They will slowly draw away any heat you put into them. Unless you want to be pre-heating for hours on end, you only want a ceramic hearth, with all other sides being aluminized steel.

The radiant element, imo, is worthless for a deck oven of your size.  Both elements need to run the entire dimension of the oven.  If your interior space is, say, 430mm by 430mm, you need an element that fills that space.  That's how the P049s are set up.

If you have any hope in pulling this off, I highly suggest mimicking the P049- to an extent.  Steel walls and ceiling, space for one pizza, one deck, a broiler element that runs the entire interior dimension and a baking element of the same size beneath the stone. The only changes I would make would be to decrease the vertical height (better top browning with a weak element) and go with a thicker stone.  I don't know the exact thickness of the P049 stone, but it's par for the course for these ovens to use woefully thin stones.  You might be able to get away with 19mm thick kiln shelves, but I would go with 25 mm just to be safe. It's better to have to pre-heat for a bit longer than to have a stone that can't cook more than one pizza.

The P049 burners aren't bad, but I'd still like to see something squarer with the coil filling the whole square. For instance, if you look at this element here:

http://www.ebay.com/itm/EL93-LINCAT-PO49-PIZZA-OVEN-HEATING-ELEMENT-240V-2KW-/140591304477?pt=UK_BOI_Restaurant_RL&hash=item20bbe50f1d

you'll see it quotes a dimension of 495mm width x 434mm length (inc terminals), but in reality, you can only bake a pizza under the coiled area, so the actual working size is in the vicinity of 495 x 330. You want a square working area to accommodate one single round pizza- ideally, a square element in the 410 x 410 realm and an oven that's only a few mm larger- maybe 420 x 420. 2.9kW doesn't have a hope in heck of pumping out enough heat for a single 614x458mm deck. You need to think smaller, much smaller.

Edit: I'm not in love with the wattage, but can you see how the coils in the element are a bit squarer than the one above?

http://www.ebay.ie/itm/LINCAT-PO49X-PO89X-PO69X-PIZZA-OVEN-HEATING-ELEMENTS-/140590363099?pt=UK_BOI_Restaurant_RL&hash=item20bbd6b1db

Edit2:  At the end of the day, when you start looking at how much you're going to invest in this project, a project that may not even give you the results you're looking for, isn't the prospect of buying a real oven for your kitchen at least a little bit enticing?  If you've got a butane gas kitchen oven that can only bake a pizza in 18 minutes, it has to be anemic enough to be failing you for other foods as well. That oven has to be driving you a little crazy, correct?  A generic electric home oven that can hit 287 C. can't be that expensive, even in France- you end up with a real oven that will work for other foods, and there's zero risk.  You buy the oven and it will make great pizza.
« Last Edit: November 14, 2011, 06:29:40 AM by scott123 »

Offline crosbie

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Re: Home made electric twin deck
« Reply #4 on: November 14, 2011, 09:18:56 AM »
Thanks Scott123, for helping me out here.

Crosbie, if you have 3" of kiln stones on all sides, with those elements, it will take quite a few hours for the oven to reach a suitable temp for pizza.  Very thick stones act like sponges.  They will slowly draw away any heat you put into them. Unless you want to be pre-heating for hours on end, you only want a ceramic hearth, with all other sides being aluminized steel.


Yes, it's possible it could take two hours (or more?  :-\ ), but if the only place that heat can go is back in to the pizza that's put on it, or into the cold air that enters when the door opens, then that seems very useful latent heat (given one only has domestic 3kW rather than commercial 30kW to play with). And I have a hunch that it's preferable to do 'something else' for a couple of hours while the oven warms up at 3kW than install a 3 phase 30kW supply in order to have a 10 minute pre-heat time and the luxury of an oven with relatively thin metal walls (and a big heat extractor vent above).

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The radiant element, imo, is worthless for a deck oven of your size.  Both elements need to run the entire dimension of the oven.  If your interior space is, say, 430mm by 430mm, you need an element that fills that space.  That's how the P049s are set up.


I can see that one might wish to put the pizza under the 43x43cm element if in the rear of a space of 65x43cm. I figure the heat that goes into the 'wasted' stones around the 22x43cm unused space near the oven door will serve as a buffer zone between the hot end of the oven and the end cooled by the door opening.

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If you have any hope in pulling this off, I highly suggest mimicking the P049- to an extent.  Steel walls and ceiling, space for one pizza, one deck, a broiler element that runs the entire interior dimension and a baking element of the same size beneath the stone. The only changes I would make would be to decrease the vertical height (better top browning with a weak element) and go with a thicker stone.


If the objective was to mimick a commercial oven then I think it would be best to simply buy one, e.g. a PO49. :)

I'm thinking that in exchange for longer pre-heat, I can use a 1.5kW element to heat a far better insulated chamber with 3" all round of latent heat.

As to decreasing the vertical height, when you remove the element's 2-3cm from a chamber of 11.4cm to leave about 9cm then this is pretty low headroom (you start having to worry about calzone catching on the element).

I'm intrigued as to how different a pizza would come out if either in a 400C oven with top element ON continuously or in a 500C oven with top element OFF continuously (given 3" thick kiln stones all round with 400/500C surface temp @ 120min pre-heat).

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I don't know the exact thickness of the P049 stone, but it's par for the course for these ovens to use woefully thin stones.


Commercial users can no doubt spare the electricity to compensate for thin stones from their profits on sales.

Quote
You might be able to get away with 19mm thick kiln shelves, but I would go with 25 mm just to be safe. It's better to have to pre-heat for a bit longer than to have a stone that can't cook more than one pizza.


Sure.

Quote
The P049 burners aren't bad, but I'd still like to see something squarer with the coil filling the whole square. For instance, if you look at this element here:

http://www.ebay.com/itm/EL93-LINCAT-PO49-PIZZA-OVEN-HEATING-ELEMENT-240V-2KW-/140591304477?pt=UK_BOI_Restaurant_RL&hash=item20bbe50f1d

you'll see it quotes a dimension of 495mm width x 434mm length (inc terminals), but in reality, you can only bake a pizza under the coiled area, so the actual working size is in the vicinity of 495 x 330. You want a square working area to accommodate one single round pizza- ideally, a square element in the 410 x 410 realm and an oven that's only a few mm larger- maybe 420 x 420. 2.9kW doesn't have a hope in heck of pumping out enough heat for a single 614x458mm deck. You need to think smaller, much smaller.


I've actually already availed myself of a couple of those EL93 elements from that very vendor. :)

They are unsurprisingly a tad flexible - enough to squeeze into the 61x46x11cm deck I plan to build (dual).

The loops are about 42cm peak to peak.

For a metal cabinet I would completely agree that 1.5kW would be insufficient for one deck. However, given extremely low heat loss (a temperature gradient from interior to exterior of 500C to ~40C) then I reckon the 1.5kW should be ample to reach 500C - and hopefully just enough to recover after door opens and 1 or 2 pizza enter.

Quote
Edit2:  At the end of the day, when you start looking at how much you're going to invest in this project, a project that may not even give you the results you're looking for, isn't the prospect of buying a real oven for your kitchen at least a little bit enticing?  If you've got a butane gas kitchen oven that can only bake a pizza in 18 minutes, it has to be anemic enough to be failing you for other foods as well. That oven has to be driving you a little crazy, correct?  A generic electric home oven that can hit 287 C. can't be that expensive, even in France- you end up with a real oven that will work for other foods, and there's zero risk.  You buy the oven and it will make great pizza.


I was going to simply buy a Lincat PO49x, but then the "Because it's there!" mentality hit me. I figured that perhaps the commercial ovens are optimised for high throughput rather than thermal efficiency, and I could make a different trade off, i.e. longer warm-up + better thermal efficiency for low throughput.

But yeah, I hate the gas oven I have to put up with, but having adjusted the cooking times accordingly I can just about end up with pizza that remains pleasurable to eat. The local professional pizza tends to have soggy bases and is primarily cheese puddles with your choice of meat/veg underneath.

Some brits around here consequently take the wood burning oven route, but that's a much bigger step for the few afficionadoes I reckon than getting an outdoor electric oven that takes 1-2 hours to warm up with zero maintenance.

buceriasdon

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Re: Home made electric twin deck
« Reply #5 on: November 14, 2011, 02:25:53 PM »
Is the plan to use soft insulting bricks for the oven lining walls or hard refractory bricks?
Don

Offline crosbie

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Re: Home made electric twin deck
« Reply #6 on: November 14, 2011, 02:31:47 PM »
Is the plan to use soft insulting bricks for the oven lining walls or hard refractory bricks?
Don


I fancy the '42GD Firebricks' as described on http://kilnlinings.co.uk for the lining. I had half a mind to use softer '26GD' bricks for the oven ceiling given it was unlikely to have any wear/contact, but I may be persuaded to use 42GD for their strength anyway.

buceriasdon

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Re: Home made electric twin deck
« Reply #7 on: November 14, 2011, 02:48:44 PM »
I would use the 23G for insulation and shorter ramp up time. Insulating bricks reflect heat not absorb it. I don't see any advantage to using hard brick in this application.
http://kilnlinings.co.uk/index.php?main_page=index&cPath=11
Don



I fancy the '42GD Firebricks' as described on http://kilnlinings.co.uk for the lining. I had half a mind to use softer '26GD' bricks for the oven ceiling given it was unlikely to have any wear/contact, but I may be persuaded to use 42GD for their strength anyway.

Offline crosbie

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Re: Home made electric twin deck
« Reply #8 on: November 14, 2011, 03:14:52 PM »
I would use the 23G for insulation and shorter ramp up time. Insulating bricks reflect heat not absorb it. I don't see any advantage to using hard brick in this application.

Well, given there's only a 1.5kW heat source it seems to me that latent heat absorbed by firebricks is a bonus (at the expense of warm up time) compared to a rapid warm up to 500C with non-absorbing/reflecting insulation bricks, because the latter don't help the oven recover from an open door and cold pizza dough as much as heat absorbing fire bricks.

Perhaps you'd suggest that for domestic use with typically 2 or 3 pizzas being cooked in any one session, that the greater heat capacity of fire bricks is over engineered, that insulating bricks will have ample heat retained to release into a pizza? Perhaps it's a case of 60 mins warm-up with insulating bricks vs 120 mins warm-up with fire bricks, and the latter only being useful if pizza parties are de rigueur?

buceriasdon

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Re: Home made electric twin deck
« Reply #9 on: November 14, 2011, 04:08:02 PM »
A converted electric pottery kiln which uses insulating firebrick as most every commerical kiln I know of uses.
http://slice.seriouseats.com/archives/2011/09/wild-rise-jay-street-bar-pizza-dumbo-brooklyn-nyc.html
Why waste all that electrical energy heating up hard bricks as opposed to keeping the heat where you want? Are you going to be baking bread the next day? Plan on using it for a roast after pizza?


Offline crosbie

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Re: Home made electric twin deck
« Reply #10 on: November 14, 2011, 04:29:58 PM »
A converted electric pottery kiln which uses insulating firebrick as most every commerical kiln I know of uses.
http://slice.seriouseats.com/archives/2011/09/wild-rise-jay-street-bar-pizza-dumbo-brooklyn-nyc.html
Why waste all that electrical energy heating up hard bricks as opposed to keeping the heat where you want? Are you going to be baking bread the next day? Plan on using it for a roast after pizza?


Yeah, whether I REALLY need fire bricks is a big question. However, I wonder if I should err on the side of caution (albeit expensive) and try the high heat capacity fire bricks first, and then when I realise you're right, that they're overkill I can opt for insulating bricks on the second version of the oven?

A slight downside of the insulating bricks is that I gather they're not quite as strong structurally or for wear & tear.


buceriasdon

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Re: Home made electric twin deck
« Reply #11 on: November 14, 2011, 04:37:32 PM »
Good luck.

Offline crosbie

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Offline shuboyje

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Re: Home made electric twin deck
« Reply #13 on: November 15, 2011, 12:23:43 PM »
3 inches of fire brick is a LOT of mass.  My first brick oven had 3 inches and held heat for days after a fire.  If it were me I'd build the walls out of stainless and use 1 inch kiln shelves for the deck and dome.  Insulate the heck out of it and let her rip.  The kiln shelf will conduct better then the firebrick which should mean you will get similar results at a lower temp, a faster heat up and fast rebound.  Sounds thermally efficient to me.
-Jeff

Offline crosbie

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Re: Home made electric twin deck
« Reply #14 on: November 15, 2011, 02:36:28 PM »
3 inches of fire brick is a LOT of mass.  My first brick oven had 3 inches and held heat for days after a fire.  If it were me I'd build the walls out of stainless and use 1 inch kiln shelves for the deck and dome.  Insulate the heck out of it and let her rip.  The kiln shelf will conduct better then the firebrick which should mean you will get similar results at a lower temp, a faster heat up and fast rebound.  Sounds thermally efficient to me.

I like your thermally efficient design. Yup, the steel walls protect the insulating brick, and perhaps sufficient heat should be retained within the firebrick shelves (and to some extent in the insulating brick).

Trouble is I either need to find sheet and someone/thing to fold it, or I find a supplier of ready made cabinets (old catering ovens?). Failing that I'll bear it in mind for prototype II.

Offline scott123

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Re: Home made electric twin deck
« Reply #15 on: November 15, 2011, 05:09:23 PM »
Crosbie, re; high heat capacity firebrick...

You need to get past the idea that, as long as you insulate your oven well, whatever heat you put into it is going to benefit the pizza. Stored heat is integral to the hearth, but it's relatively meaningless in other areas. The reason for this is that conduction delivers far more energy impact than radiation in fast cooked foods.  Heat a frying pan until red hot, toss in a steak and it will sizzle, but, hold that same steak about an inch above it, and it's not going to do much. Direct contact- preheated hearth contacting the bottom of the raw dough- that's where stored heat gives you the greatest bang for your wattage buck. When you start loading the walls and/or ceiling with heat and lose that direct contact, it's like trying to cook steak above the frying pan.

Some gas deck ovens line their ceilings with firebrick.  This lining provides a slight increase in top heat, but that's only in a system where a massive number of BTUs are being pumped up the side of the oven and deflected down on top of the pizza. In an oven such as yours, where every watt counts, you don't have any extra energy to waste. You need to direct it as efficiently as possible- with a pre-heated, relatively thick kiln shelf hearth and a glowing red top element positioned relatively close to the pizza.

It sounds like you've already bought your elements, but, if you really want to hedge your bets and don't mind longer pre-heats, put less watts below the stone and more watts above- maybe 1 kW below and 2 kW above.  It'll take a while, but the 1kW bottom element will fill the hearth with the heat you require to bake the bottom of the pizza, while the 2kW element above, if glowing red, should give you the necessary heat from above to brown the top of the pizza properly.

Great pizza is about intense stored conductive heat from below and intense radiative heat from above.  All other IR is insignificant.
« Last Edit: November 15, 2011, 05:32:59 PM by scott123 »

Offline crosbie

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Re: Home made electric twin deck
« Reply #16 on: November 15, 2011, 05:40:36 PM »
Scott123, Yup I take your points on board. I was going to use fire brick for the walls (because perversely the firebricks were cheaper than insulating ones), but now I think I'll go for insulating ones. I think I'll use insulating bricks for the roof too, thus leaving the firebricks only for the floor and middle shelf (for wear & tear and heat retention).

Oh, but I think I'm going to have to use firebricks for the doors, because I don't think insulating bricks will be strong enough to support their own weight from a hinge (I suspect masonry screws will gradually rip out). I'm thinking they should be hinged on the left hand side for right handed shovelling of pizza.

With a 1.4kW ceramic rear-end-radiating element for the lower deck (also helping to heat up the middle shelf) and 1.5kW ceiling mounted element in the upper deck I'll have two differently behaving decks to play with. Perhaps the lower deck will be a pain if a pizza always needs a mid-cook 180 rotate, but I fancy giving it a whirl (I can always replace the end element with a 1.5kW ceiling element if it's a disaster). I just have a hunch that a horizontally radiating element (in conjunction with 500C pre-heated hot firebrick below & above) might simulate a wood fire in a traditional oven.  :chef:

Incidentally, I fancy one of these stuck on to the front of each deck: LCD Short Time Meter - From over 60 seconds down it is unlit, for 60-30 seconds it lights green, for 30-10secs it lights blue, and from 10-0 secs it lights red. At 0 it beeps.

Seems like it was designed for pizza times.  :pizza:

Offline scott123

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Re: Home made electric twin deck
« Reply #17 on: November 15, 2011, 06:19:26 PM »
With a 1.4kW ceramic rear-end-radiating element for the lower deck (also helping to heat up the middle shelf) and 1.5kW ceiling mounted element in the upper deck I'll have two differently behaving decks to play with. Perhaps the lower deck will be a pain if a pizza always needs a mid-cook 180 rotate, but I fancy giving it a whirl (I can always replace the end element with a 1.5kW ceiling element if it's a disaster). I just have a hunch that a horizontally radiating element (in conjunction with 500C pre-heated hot firebrick below & above) might simulate a wood fire in a traditional oven.  :chef:

It won't  :)  I'm a bit of a tinkerer myself and I applaud DIY inclinations in others.  I can feel your excitement and want to be excited for you, but the setup you're describing (2 decks, 1.5 kW each) will not work for fast baked pizza. I hate to sound like a broken record, but the only chance a 3 kW setup could be viable is with 1 deck with an element in the ceiling and an element under the hearth.

Radiative heat relies entirely on distance.  You can't viably pre-heat a hearth with a broiler.  At least, not with the vertical space you're talking about.  In order to pre-heat the hearth in a reasonable amount of time, you've got to have an element directly below it.

I guess, theoretically, if you took your present working prototype, and pre-heated it at full blast for 8 hours, you might get a fast pizza out of it, but your electricity bill is going to take a hit. You also might damage the elements and/or the wiring.

In your first post, you asked if it was plausible. If you take your limited heat and bring it all closer together so that it's actually capable of making an impact, it could be, but, as your configuration currently stands, no, it's not plausible.

Offline crosbie

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Re: Home made electric twin deck
« Reply #18 on: November 15, 2011, 06:49:56 PM »
Scott123, are you sure you're taking into account that this oven (unlike a PO49) will be extremely well insulated? Given it's neither wood fired nor gas, it can be swaddled without venting (like a thermos flask). If anything I'm wondering if humidity from pizza + toppings could cause problems to flavour/texture/browning/crispness given no venting.

I wonder if anyone has come across anyone using an electric pottery kiln for pizza, because that's probably a closer comparison than a commercial pizza deck?

Given everyone's kind and helpful comments I think my design is worth a try, and if it turns out it's only good for use as a plate warmer I can at least help others avoid my folly.  :-\    I'll let you know how I get on as I progress.

buceriasdon

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Re: Home made electric twin deck
« Reply #19 on: November 15, 2011, 07:13:35 PM »
After no small effort in searching the internet I finally found a photo of an oven similar to what I have trying to describe to you. Note: Ceramic wool blanket is bad for an oven used for baking because of floating fibers. Instead you would use light insulating brick. One of the main advantages of this type of brick is it's ability to be easily cut or drilled with hand tools, not so with with hard brick, you can't drill it except with expensive diamond drills. You can't cut it except with a water feed saw. The strength comes not from the brick itself but from the HOUSING the brick is in. The entire inside is lined with soft brick including the door. Use kiln shelf for the baking hearth with your electric elements above and below.
http://s803.photobucket.com/albums/yy317/topbarsam/Home%20made%20casting%20equipment/?action=view&current=burnout-oven-fume-hood-melting-oven.jpg&sort=ascending#!oZZ4QQcurrentZZhttp%3A%2F%2Fs803.photobucket.com%2Falbums%2Fyy317%2Ftopbarsam%2FHome%2520made%2520casting%2520equipment%2F%3Faction%3Dview%26current%3Dburnout-oven-fume-hood-melting-oven.jpg
Don


 

pizzapan