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Copper Heat Diffuser/Defroster Plate...Any Opinions? - Page 5
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Thread: Copper Heat Diffuser/Defroster Plate...Any Opinions?

  1. #41
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    mr drinky's Avatar
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    Thanks sharpmaker for sharing your experience. I definitely understand your points, and from an efficiency standpoint, a heat diffuser is probably not the best way to cook. I use mine with my cast iron dutch oven and heating it up takes a long time, and the instructions for the copper heat diffuser is to not heat it up on high, so it's slow and steady the whole way. And I would never dream of using it to boil water.

    With that said, I often use it as a defroster plate and always use it now with my dutch oven. I would never use it without now. With my gas range I used to have problems with evenness of heating, but no longer is that the case with my heat diffuser. So while it may not be a winner in terms of efficiency, IMO it is very helpful when cooking anything where you want more evenness of heating.

    k.
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  2. #42

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    I thought the whole point of a diffuser was to be an inefficient way to transfer heat...? If you want efficient thermal transfer, why put an extra piece of material between the heat source and the pan? Defrosting would seem to be the opposite though....
    Remember: You're a unique individual...just like everybody else.

  3. #43
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    Quote Originally Posted by Zwiefel View Post
    I thought the whole point of a diffuser was to be an inefficient way to transfer heat...? If you want efficient thermal transfer, why put an extra piece of material between the heat source and the pan? Defrosting would seem to be the opposite though....
    Exactly.

    k.
    "There's only one thing I hate more than lying…skim milk, which is water that's lying about being milk." -- Ron Swanson

  4. #44
    Quote Originally Posted by Zwiefel View Post
    I thought the whole point of a diffuser was to be an inefficient way to transfer heat...? If you want efficient thermal transfer, why put an extra piece of material between the heat source and the pan? Defrosting would seem to be the opposite though....
    I'm just sharing my experiences, because MC did not even MENTION the downsides to using slabs of aluminum. Yes you gain more even heating, but it comes at a price: loss of energy efficiency and loss of time. And it's worse with aluminum than copper due to aluminum's softness and ding-ability (with resultant loss of thermal conductivity), plus aluminum is more prone to warp, which is probably part of why MC recommended no less than half an inch of it. So I'm just saying, if you really want to go down that path, get an 8" diameter 1/8" or 3/16" thick copper disc (or 8x8" square). It will be enough for anything up to 12" diameter cookware (even the crappiest cookware should be able to move heat a paltry 2 inches, on either side of the copper disc's edges; plus 12" skillets often have bottom diameters less than 10" so you really only need to worry about >12" saute pans), won't warp or ding as much as aluminum, and it won't cost THAT much more if you get it from a local scrap dealer or something.

    I originally HAD to get a slab of copper to deal with my 13+ quart cast iron oval dutch oven which was too big for any one burner, so the 12x24" 3/16" slab was to help it even out. (I eventually got rid of the 13+ quart oval dutch oven because it was too much of a pain in the butt to work with and wouldn't easily fit into ovens, either... ovens by the way are a great way to get around uneven heating.) I got a few more copper plates but eventually gave up on the concept because it was energy- and time-inefficient and a pain to clean up. Induction for me, with appropriate cookware (like my Demeyere skillets which have 3.7mm aluminum wrapped in about 1.1mm of stainless steel), works much better and is easier to clean (saves time.. no more cleaning the black buildup on the copper plate or the burner or the hob) and more efficient (time and money). However, induction has a very high startup cost for those who already have natural gas or electric. If you are interested in induction, you can give it a try with portable countertop units of at least 1300W (for boiling water or lower-temperature stuff like sauteing). 1800W is the max for most such units due to the limitations of 110V 15amp wall sockets but you only need to go that high if you want to sear a steak or something. If you have 220V wall sockets you can get pro-grade portable units or simply replace your gas/electric range with an induction unit. The cheaper units will have very small coils, maybe 4 inches or less, while the more expensive induction cookers will have larger-diameter coils; coil diameter is analogous to burner diameter, so buy accordingly.

    Time is money. And money is money, too, in terms of electric or gas bills.

    That said, I don't want to turn this into an induction cooking thread, so I will just end by repeating my recommendation of copper diffuser plates over aluminum for reasons I've stated in this post and my previous post in this thread.

  5. #45

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    I think I understand your point now. BTW Mr. Drinky: I didn't ever see a report on your experience with the aluminum vs copper diffusers....
    Remember: You're a unique individual...just like everybody else.

  6. #46
    Quote Originally Posted by mr drinky View Post
    Thanks sharpmaker for sharing your experience. I definitely understand your points, and from an efficiency standpoint, a heat diffuser is probably not the best way to cook. I use mine with my cast iron dutch oven and heating it up takes a long time, and the instructions for the copper heat diffuser is to not heat it up on high, so it's slow and steady the whole way. And I would never dream of using it to boil water.

    With that said, I often use it as a defroster plate and always use it now with my dutch oven. I would never use it without now. With my gas range I used to have problems with evenness of heating, but no longer is that the case with my heat diffuser. So while it may not be a winner in terms of efficiency, IMO it is very helpful when cooking anything where you want more evenness of heating.

    k.
    Oh yeah, I agree it's a great way to diffuse heat. I just wish Modernist Cuisine at least mentioned the drawbacks and had compared aluminum to copper plates given that even copper plates are quite affordable so spending a little extra for a harder metal would seem like a good deal imho. It's not even spending that much extra because you will get paid back with faster heating and thus lower energy bills and also save time (compared to using a 1/2" thick or more aluminum plate). And yes you can also defrost with it or cool down a pressure cooker quickly or whatever with a copper plate. The heat reservoir effect is also good for searing steaks since thin pans alone could lose a lot of energy when you toss relatively cold metal onto them.

    One way of looking at this: using a thick slab of aluminum or copper is like transforming all of your non-cast iron cookware into cast iron cookware EXCEPT that this time, it's even heating (http://www.seriouseats.com/2010/02/e...n-cooking.html shows how uneven heating real cast iron is). If someone is ok with the relatively slow pre-heating process of cooking with cast iron, they are probably also ok with using a heat diffuser plate.

  7. #47

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    Sharpmaker, I guess the disconnect on this issue is: If you can't lower the heat output of your heat source to the point at which the thermal conductivity dampens it to the required level, you'll want WORSE thermal conductivity. This is entirely dependent on the equipment and process involved though...of course, this scenario is the only* reason why you'd want a diffuser for cooking (vs defrosting) in the first place.Induction is a good alternative to this though.*I suppose pots/pans that heat very unevenly could also be a reason, but I doubt many folks here have that issue.
    Remember: You're a unique individual...just like everybody else.

  8. #48

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    While the conclusions are correct in the serious eats article, I disagree with the reasoning. The hot spot I am more than convinced is metallurgical in nature. But, cast iron shines in an oven and I don't think there is any dispute of it's even heating properties in the oven. The diffuser is mimicking the oven I believe on a cast iron pot, albeit poorly as Sharpmaker has described.

    -AJ

  9. #49
    Quote Originally Posted by Zwiefel View Post
    Sharpmaker, I guess the disconnect on this issue is: If you can't lower the heat output of your heat source to the point at which the thermal conductivity dampens it to the required level, you'll want WORSE thermal conductivity. This is entirely dependent on the equipment and process involved though...of course, this scenario is the only* reason why you'd want a diffuser for cooking (vs defrosting) in the first place.Induction is a good alternative to this though.*I suppose pots/pans that heat very unevenly could also be a reason, but I doubt many folks here have that issue.
    I would not phrase it that way. You almost NEVER want WORSE thermal conductivity. If you wanted to keep the sentence structure of what you wrote, I would rephrase it like so: "If you can't lower the heat output of your heat source to the point at which the thermal conductivity dampens it to the required level, and you can't change your cookware, then you will want to buffer it with an underlayer of material. How thick that underlayer of material has to be to achieve even heating depends on the thermal characteristics of the material--the more thermally conductive the material is, the thinner that layer has to be."

    My points were to address MC which framed it this way: ideally you would want a burner diameter to be pretty close to the diameter of the bottom of your cookware and for your cookware. (The middle of the pan is less of a problem since heat doesn't have anywhere to go but into the food anyway; it's the edges of the pan that keep losing heat and thus need heat replenishment continuously). But what if your largest burner isn't very large?

    You have these options:

    1) get a new cooktop with larger burners
    2) don't use larger-diameter cookware on undersized burners
    3) get more thermally-conductive cookware
    4) get thicker-bottomed cookware
    5) expand the size of the burner via plates/sheets/slabs/whatever of metal

    1) and 2) aren't always realistic, so the real debate is on 3) vs 4) vs 5), and many people don't want to replace cookware so it's really just a discussion of 5).

    Regarding 5), MC and I diverge on the value of thermal conductivity here. MC does not seem to care much about thermal conductivity and diffusivity, as they even recommend thick steel. MC greatly stresses how thickness is FAR more important than thermal qualities of the material going so far as to put steel in the same sentence as aluminum, which is crazy. It would be only a slight exaggeration to say that in MC's fantasy world, you should just find the lowest-density material available and use that as your heat diffuser, regardless of how good or bad of a thermal conductor it is. That way you maximize thickness without increasing weight to the point where you can't lift the plate up anymore.

    MC isn't entirely wrong, but the truth is more complex. Thermal conductivity and diffusivity DO MATTER when it comes to even heating. This has been proven repeatedly, such as at http://www.seriouseats.com/2010/02/e...n-cooking.html (The cast iron was about 6mm thick and was very uneven-heating compared to the All-clad stainless pan which is roughly 3mm thick, of which roughly 2mm is aluminum and the rest stainless steel.) For a list of thermal conductivity numbers see http://www.engineeringtoolbox.com/th...ity-d_429.html

    The fact of the matter is, the better thermally something is, the thinner you can get away with making the slab and still achieve the same degree of even heating. The thermally worse stuff needs thicker thicknesses to achieve the same degree of even heating.

    MC says use plates of aluminum 0.5 to 1.5 inches (12.7mm to 38.1mm) thick. IMHO that is overkill for most people. Let's put this in context. All-Clad (and its clones like Cuisinart MCP, Calphalon, etc.) have only 1.6-2mm of aluminum. MC is basically saying with a straight face that in order to have even heating, you need an aluminum layer 6.35-24 times thicker than what you find in tri-ply clad, IN ADDITION TO what you already have in your pans themselves. (Either that, or aluminum is even worse than I thought about warping, and you need at least 0.5 inches thickness to guard against aluminum slabs warping over time. Which actually sounds about right, now that I think about it.)

    What I'm telling you is that 1/8th thick copper (~3.2mm copper) is good enough for most realistic scenarios (i.e., putting your largest pan on your largest burner, not putting your largest pan on your smallest burner). A 1/8th-inch (3.2mm) thick copper slab is roughly equivalent in heat-spreading power to 4mm of aluminum due to copper's superior thermal conductivity and diffusivity. And you add that 3.2mm of copper to whatever you ALREADY HAVE in your cookware, such as the 1.6-2mm of aluminum in All-Clad. But beyond sheer heat-spreading power, copper is simply more efficient at transferring heat, so you have less pre-heating wait time and wasted energy (heat that goes into your kitchen rather than your pot); plus copper is harder than aluminum so it can take more abuse before getting dinged up or warping.

    Quote Originally Posted by ajhuff View Post
    While the conclusions are correct in the serious eats article, I disagree with the reasoning. The hot spot I am more than convinced is metallurgical in nature. But, cast iron shines in an oven and I don't think there is any dispute of it's even heating properties in the oven. The diffuser is mimicking the oven I believe on a cast iron pot, albeit poorly as Sharpmaker has described.

    -AJ
    ANY metal is going to heat evenly in an oven because heat is bombarding the material from all directions. There is nothing special about cast iron in that respect; a copper, aluminum, or stainless steel dutch oven will also heat evenly. (The biggest advantage of cast iron dutch ovens inside of ovens is the heavy lid sealing in moisture, whereas you may need to weigh down the lid with something if you use, say, a flimsy aluminum dutch oven.) A stove is different, where you have a hot heating element circle at one extreme end of the cookware (the bottom end). A square or circle heat diffuser is essentially stretching that little heating element circle and making it into a solid square or circle. This has the effect of evening out the heat on the bottom.

  10. #50
    I can't edit my post anymore but I would like to add that copper of 3.2mm actually has heat-spreading power more like 5.6mm-thick aluminum, not 4mm, going by thermal conductivity. I was a little too conservative. The point remains though that 3.2mm copper is already plenty thick enough for even heating.

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