Aluminum foil

[stonecutter]

Re: Aluminum foil

Logically, how could a thin, highly conductive layer like foil have value acting as a heat reflector, especially without facing the source of radiant heat ie: the fire itself and is directly in contact with the thermal mass?

Since we discussing the science behind it, where's the evidence that shows that foil can reflect more heat than it conducts? Without insulation behind it, foil will suck heat out of the oven brick as fast as additional mass would. The science proving foil is a poor component to an oven build, is because of the physical properties of the material (aluminum) itself.

The thing about masonry is that it needs to breathe. Anytime you hinder that mechanism, steps need to be taken to facilitate the elimination of moisture. David found that out, and poked holes in his foil. Gulf incorporated a vent to release moisture in his shell. And I have seen how buried aluminum reacts to the alkalis in mortar when it is in direct contact or not. The oxidation damage will vary depending on the amount of moisture and oxygen the aluminum is exposed to. The damage to the material will vary build to build, location to location depending on the application.

[NCMan]

Re: Aluminum foil

Sorry, it seems I touched some of your triggers. I didn't mean to upset you. I still think it's a huge benefit to explain the science if you are arguing from a scientific standpoint and even more especially if your audience might not have the same level of thermodynamic understanding. I spent all morning on the internet looking up stuff I've long forgotten because I really wanted for me to be right and you to be wrong. I agree with you now but if you don't actually cite references and/or prove your point conclusively some way I'm more inclined to disagree just because I really dislike unsuported statements claiming to be absolute (one of my triggers). I still am not sure if I really understand the pyhsics behind why it doesn't work so if you could enlighten me (and probably a few more here) I would be grateful.

My first post in this thread was off the cuff and meant to be humorous/inspire debate and was of course not all that well thought out as I now disagree with myself.

No triggers here and you certainly did not upset. I just get tired of people wanting to argue w/facts. Opinions, all are welcome. I also don't believe for a second that you were being off the cuff w/your original post. You had a building method, even bragged about how well it worked and wanted to know what others thought. You had, I believe, a few experienced and knowledgeable builders answer you....w/facts. Personally, I'm here to share my personal experiences w/my Build, as well as having a keen interest in the Builds of others. If someone asks for an opinion, if it is something I have knowledge about, I will offer assistance, usually in the form of an opinion, based on my past training and experience. But....there are differences in stating proven facts and obvious opinions. What works for one Builder may not for another. I get that. Opinions, we can share and even debate. I love it. People arguing w/proven science, not so much.

[cobblerdave]

Re: Aluminum foil

G'day
A couple of years ago I built ? Not really I mucked around with a dry stacked oven. Build with bricks that had been lying on the ground and it cooked a reasonable enough pizza for the days efforts.
Next weekend with that little oven a lot dryer (cured?) became to be positively hot with use so next day we got serious about the heat. We wrapped that thing completely with layers of aluminum foil, bricked the entrance off and cut off the front excess.
Worked well enough for our efforts and didn't burn anyone. As for great heat retention well I don't think so , but it you could touch the outer surface without burning your hand.
The " oven " didn't survive much past this ... But was a lot of fun.
On the serious side if you do use aluminum try this.
Cover a brick with aluminum foil , put it in your yard , on the ground , a week .
The top might be a bit duller but the bottom,i out of the air and moist,bet you its going black and not looking as robust !
Regards dave

[william]

Re: Aluminum foil

Thanks pyg
I learned a few things here also

[pyg]

Re: Aluminum foil

I've stated my opinion on this, which is backed up by proven science. I don't see a need to explain proven science. People that want to use foil can go for it.

Sorry, it seems I touched some of your triggers. I didn't mean to upset you. I still think it's a huge benefit to explain the science if you are arguing from a scientific standpoint and even more especially if your audience might not have the same level of thermodynamic understanding. I spent all morning on the internet looking up stuff I've long forgotten because I really wanted for me to be right and you to be wrong. I agree with you now but if you don't actually cite references and/or prove your point conclusively some way I'm more inclined to disagree just because I really dislike unsuported statements claiming to be absolute (one of my triggers). I still am not sure if I really understand the pyhsics behind why it doesn't work so if you could enlighten me (and probably a few more here) I would be grateful.

My first post in this thread was off the cuff and meant to be humorous/inspire debate and was of course not all that well thought out as I now disagree with myself.

[NCMan]

Re: Aluminum foil

I'm saying this because it's a fact, backed up by proven science. I personally don't see a need to explain proven science, nor argue w/someone about it. People that want to use foil can go for it.

[pyg]

Re: Aluminum foil

Pure waste of time. It will not work at all, especially w/no air gap, as I and others have said.

I'm guessing you are saying this because in an oven type thermal mass the heat transfer is primarily conductive until it reaches the air and then is primarily radiant and convective. Aluminum is a great conductor so putting it next to the bricks doesn't stop conductive transfer at all. I wanted to argue that the aluminum should reflect the infrared anyway but if it comes up to the same temperature as the bricks it will be radiating itself. I even did a little experiment and put some aluminum on a hot surface and checked the surface and the foil covered surface with an infrared thermometer an there was little difference. Anyway, I think it's more helpful to explain why instead of just saying it's a fact.

[NCMan]

Re: Aluminum foil

Pure waste of time. It will not work at all, especially w/no air gap, as I and others have said.

[pyg]

Re: Aluminum foil

Foil works as a radiant barrier, reflecting heat. To do this, it needs an air gap between it and other materials. Not really possible in the Pompeii oven design. I'm sure your oven worked great, but you'll probably find that the design used by most builders here will work better.

Aluminum has a reasonably high melting temp for WFO applications (666C as it needs to break down in hell readily) so it would survive next to the firebrick/cladding fine and might do good. It also oxidizes readily and is then quite inert as Al2O3 so long term fears of acid/base corrosion are probably not realistic. Although the shiny side reflects photons slightly better the side you face in will make no difference and should 'theoretically' make some difference in the infrared spectrum. For the cost involved I say do it and put it right next to your thermal mass two layers thick... probably a better plan than buttering the outside of the dome with hitemp mud imo and a whole lot cheaper.

[william]

Re: Aluminum foil

Yes K26 with Itc coating remarkable stuff

[david s]

Re: Aluminum foil

You would have presumably used Insulating fire bricks, in which case ther wouldn't be much heaton their outsides.

[william]

Re: Aluminum foil

Hi David
My kiln are electric, I have built them to do larger scale art glass pieces, I have also built electric furnace for blowing glass but for me that's just for fun, if you like take a look at my website, wgrixartglass.com. I used the foil behind the facebrick in the furnace before the insulation. that runs at about 2000 degress foil was intact for about three rebuilds.
Bill

[deejayoh]

Re: Aluminum foil

Foil works as a radiant barrier, reflecting heat. To do this, it needs an air gap between it and other materials. Not really possible in the Pompeii oven design. I'm sure your oven worked great, but you'll probably find that the design used by most builders here will work better.

[david s]

Re: Aluminum foil

Hi David
The oven I was speaking of was on the leeward coast of Oahu we saw very little rain there, The one I am going to build is in a much wetter location as I am on the side of a mountain in the interior of the island. You make some very good points and I will forgo the foil on this one.

Sorry if I veered off my opinion topic with this

Thanks
Bill

Don't apologise Bill, the discussion here is exactly on the topic you raised. Many of our threads get way sidetracked. The beauty of this forum is that folk can share opinions and experiences from all over the world.

I would like to know more about your glass slumping kilns, having built a number of kilns myself. Are yours fuel fired or electric? If fuel fired what do you use and does it affect the colours in the glass?

[william]

Re: Aluminum foil

Hi David
The oven I was speaking of was on the leeward coast of Oahu we saw very little rain there, The one I am going to build is in a much wetter location as I am on the side of a mountain in the interior of the island. You make some very good points and I will forgo the foil on this one.

Sorry if I veered off my opinion topic with this

Thanks
Bill