Foil and ovens

[combo52]

Dual side up?

I seriously doubt it would make any difference at all, but in any case it would be better to reflect and keep as much heat in the oven as possible.

 

[kenwashesmonday]

Yes, dull side up.

As someone who would often use the thermocouple attachment on his Simpson 255 multimeter to perfectly set the customer's oven temperature, I doubt very much that my dad was guessing.

Ken D.

 

[kb0nes]

The difference in reflectivity from either side of the foil is insignificant. Although it may be measurable.

Using a bare bulb thermocouple to measure oven temperature add a problem in itself. The infrared heat from both the elements acts directly on the low mass thermocouple and it skews the measurement causing it to read high and exhibit excessive variation. The only way I have seen reasonable measurements in my oven if to place the thermocouple inside a radiation shielding sleeve, otherwise the measurement trend shows wild variations. Somewhere I have graphs of with and without the sleeve. I saw differences of over 15 degrees with my thermocouple.

The mass of the thermostat sensor in the oven is much higher so as to normalize the effects of radiation so the air temp set point really shouldn't change. Imagine the difference in reflectivity just by adding the foil over the oven bottom, that could be significant. The dull vs shiny side surely isn't.

Of course the manufacturer will add wording in their documentation to not use the foil. This is all typical cover their ass boiler plate to limit liability. People do all kinda of foolish stuff and legal departments exist to protect the company. As long as the foil doesn't short the element or cover vents, physics is on the side of it causing no problem.

Damage to the inside of the oven or bonding to the porcelain? I could only see that if someone ran it through the self clean cycle of if the oven had concealed elements perhaps. Damage to the calrod bake element from radiation? I just don't see that, the thermal difference to the element could be no more then a few degrees, a small percentage of 1000 Deg F. [this post was last edited: 12/12/2015-11:10]

 

[magic_clean]

Foil on the oven floor--not recommended!

Excerpt from a Use and Care guide for KitchenAid wall ovens, which have had hidden bake elements since 1996:

Aluminum Foil

IMPORTANT: "To avoid permanent damage to the oven bottom
finish, do not line the oven bottom with any type of foil or liner."

 

[kenwashesmonday]

The Simpson 255 multimeter was aimed at the appliance repair trade. The thermocouple attachment was designed for checking oven temperatures. Note that the more common Simpson 260 lacks the temperature scale.

See link below.

Simpson 255 / Volt - Ohm - Milliammeter

www.simpson260.com

 

[kb0nes]

Ken,

I know the Simpson meters well, I had one on my bench at my first electronics job 30 years ago, but this has nothing to do with the meter itself. The photo shows the meter I used last in my oven, a graphing Fluke 289. I won't mention the difference in meter accuracy, but that is because again it isn't the issue.

The issue is that a simple bead style thermocouple (as shown in the page you referenced) has a tiny amount of thermal mass. This has the advantage of making measurements really responsive since there isn't a lot of thermal "inertia" to overcome as temperatures change. In this case the infrared radiation that comes off the elements directly heats the thermocouple resulting in erroneous readings if we are trying to read air temp. I found that unless I had the thermocouple inside a radiation shield (I used an aluminum foil tube) I had no idea what I was reading, it wasn't just air temp.

There is a definite possibility that adding the foil in the bottom of the oven could cause a measurable temperature difference in the oven. Of course the different reflectivity may alter cooking just due to the infrared energy which isn't shown in the actual cavity air temp. But my point is that the difference between the shiny side and the dull side is tiny compared to installing the foil in the first place. If your thermocouple doing the measurement is unshielded and responding to the infrared energy there is a chance you could see shiny side vs dull side (reflectivity difference is ~5% at IR) but it really isn't worth any concern.

 

[combo52]

Using Foil Liners On Oven Floors

Whirlpool sells SHINY aluminum foil for the oven floor of their Continuous Clean ovens, And yes no one is suggesting putting foil on the floor of a hidden element electric oven, and for that matter it is really not a good idea to put foil on the floor of a gas oven even if you do not block the oven floor vents because a lot of heat in a gas oven also comes through the metal oven floor.

 

But I agree that using the shinny or dull or side would likely make no difference, on most aluminum foil you can hardly even see the difference from one side to the other, LOL.

 

[kenwashesmonday]

Well then it would seem that the information and equipment supplied by General Electric to their Factory Service Techs was no good. It would also seem that the makers of Reynolds aluminum foil since 1947 are mistaken and have no clue whatsoever how their product should be used, as both claim "dull side up". Oh, and as for the makers of the legendary Simpson meters, it would appear by this thread they they didn't know what the hell they were doing either.

General Electric, Reynolds Aluminum, and the Simpson Electric Company were all clueless.

Ken D.

 

[cuffs054]

Here we go! I was never sure of which side to use for anything. If you're covering meat, cassorole, etc. which is correct? The Reynolds non-stick (magic!) has the non sitck side on the dull side. Why is the universe so complicated?

 

[DADoES]

 
I have in the past run across a statement from Reynolds that the shiny vs. dull sides are related to how the sheet is run through rollers during production and that there's no effective difference between them in use.

 

[alr2903]

Back in my teen days Sizzler demanded baking potatoes have the shiny side toward the potato.  A lot of talk about cooking efficiency.  Maybe more about consistent appearance?

 

[combo52]

Whirlpool Oven Liner Foil

Whirlpool still sells oven liner foil Pt# 241430, they list it as fitting about every brand oven that WP ever had anything to do with.

 

This foil is the same on both sides and is VERY shinny.

 

[askolover]

My daddy used to roll out the foil on the mills at Reynolds.  They would give the employees free packages of wrap when the plant had open house.  As far as wrapping food goes, it makes no difference which side goes against the food.  As was stated above, it's the way it runs through the mill that makes one side dull.  As far as oven floors, I have no clue.

 

[norgeway]

I ALWAYS

Use it shiny side up!..And have never had a problem.

 

[tolivac]

Don't use foil in my ovens-don't see the need.For my brand new GE Advantium oven-replaced my orig one that was 15 years old-the manual for it warns explicitly NOT to use foil ANYWHERE in the oven.The GE Advantium(240V) is a microwave,speed cook,and convection oven in one machine.It also has a rangetop exhaust fan and light.Been very happy with these.My regular GE-Hotpoint oven gets little use.

 

[perc-o-prince]

DADoES and askolover

I saw the "How's It Made" or similar show about the foil. It's because the foil is run through doubled. The faces that are pressed together turn out one way, and the faces against the rollers turn out the other. I forget which is dull and which is shiny, however.

Chuck (I never check which side I'm using unless it's for show; then it's shiny-side up for visual effect.)