The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Cast Iron Cooker vs. Granite Ware -Thermal Data-

DanAyo's picture
DanAyo

Cast Iron Cooker vs. Granite Ware -Thermal Data-

Formerly a huge advocate of cast iron cookers, I have become evangelized by TrailRunner, aka Caroline. After much dissent, I conceded to Caroline's persistence and decided to give the Granite Ware (GW) a try. I thought, how could a light weight cover hold anywhere near the heat as a heavy weight cast iron cooker (CIC)? Against everything my common sense was screaming at me, I started testing.

Originally I tested by simply shooting the heated vessels with an Infrared Heat Gun. The temps were leading me to accept Caroline's assertions. The gun showed that the GW heated up and also recovered heat much faster than the CIC. The GW also lost heat much faster than the CIC. For months I rejected the use of the CIC in favor of GW. A couple of days ago I spoke with my nephew who is, believe it or not, a rocket scientist (engineer). I wanted to learn about emissivity. He works as lead thermal engineer for the US Space program at Martin Marietta. During our conversation we came up with the following idea. And after today's test the rest is history...

Last evening I started a couple of 550g boules. They were placed into the retarder and a temperature data log was setup. The data log for the dough retarder can be viewed HERE. NOTE - if you play with the log you will discover that a number of options are available e.g. the ability to position the cursor in the timeline and get all 3 temperature readings. This morning the test began. The goal was to compare in real time, the ambient temperatures inside the vessels used to bake the bread.The oven was set to bake @ 500F for the first 20 minutes and then once the covers were removed reduced to 425F convection for a total of 30 minutes cook time. A Fibrament-D stone was used as the deck. The GW vessel used can be seen HERE. The CIC can be seen HERE. The GW cover and also the CIC top and bottom were predheated @ 500F for about 1 1/2 hours before the bake commenced.

The tips of the temperature probes needed to be situated in such a way as to have them exposed to open air inside each vessel. To accomplish that, the probes where placed through the bottom of each dough and left protruding through the tops. The probe on the open deck seen above is for the ambient temperature.

The doughs were loaded and the data log starter. Below is a screen shot, but the actual data log for the bake can be seen HERE. Note the chart at 9:27, commence bake and 9:49, open oven and remove lids. Below is a static screen shot of the graph.

The following data may be of interest. All temps are Fahrenheit.

The initial temperature of the doughs were 44°. 

These temperatures were taken just before the dough was loaded. Stone - 529, floor of oven - 568, CIC - 504, GW - 512.

Both vessels were measured with an infrared heat gun for temperature at the following times. 30 seconds out of oven: CIC - 426, GW - 336. 1 1/2 minute out: CIC - 352, GW - 175. 3 minutes out: CIC - 304, GW - 131. 5 minutes out: CIC - 259, GW - 117. After only 3 minutes out of the oven the GW was easily handled. A great safety feature.

Conclusion - Granite Ware is light weight and inexpensive. To be most effective a stone or something similar should be used for the deck. Although it loses heat extremely fast, it also recovers heat equally as fast. The bread in the Granite Ware vessel almost constantly hovered around 65° F above the Cast Iron Cooker. 


I am always inspired by the scientific information shared by Doc.Dough. I only wished I could comprehend more of it :-(    I did my best to execute this experiment with his expertise in mind. I know had he conducted it, we would have more scientific information available. But this is a country boy's best effort ;-)

Danny

 

franbaker's picture
franbaker

Thanks for sharing some really helpful info :-)

Yippee's picture
Yippee

I just ordered a gw roaster last night. I'm hoping it will replace the boiling water method, which has caused a lot of stress for me.  Cast iron is too heavy, so have never considered it an option.

Yippee

texasbakerdad's picture
texasbakerdad

I am interested in your experiment, but the fireboard link is going to something else, something titled "Compact Dough Retarder".

EDIT: Oh, I misunderstood your post, I should have clicked the link lower down.

DanAyo's picture
DanAyo

I checked a data log links and they look correct. One log is for the retard and the other is for the bake. Please check it out and if you still see an error, let me know and I’ll correct if necessary.

Dan

texasbakerdad's picture
texasbakerdad

Dan,

Yes, the links are good. I misread your post and thought the first link was for the cover testing. Thanks!

texasbakerdad's picture
texasbakerdad

Were the lids preheated? If I am reading the post correctly, I am guessing they were not preheated. Correct?

DanAyo's picture
DanAyo

The GW cover and also the top and bottom of the CIC were preheated.

Dan

texasbakerdad's picture
texasbakerdad

Do you have the temperature profile of the preheat? I'm curious if the cast iron and the granite-ware ever got up to the 500 dF set temperature. The the fireboard chart shows high temps starting at 9:28, but that is when you said the bread baking started. I guess the temperature probes didn't go into the oven until the moment the bread baking started. Which is fine, I am just checking to make sure I understand everything properly.

texasbakerdad's picture
texasbakerdad

I like your experiment... I hope you don't mind me delving into it further.

Some insight into why I am asking this question. If the cast iron and the granite-ware had started at 500 dF or near 500 dF, I would have expected to see the chart show a steady drop from 500 dF for both of them as the covers absorbed the cool water vapor emanating from the loaves.

It seems that one of two things happened:

  • The cast iron lost 100 dF and the granite-ware lost 85 dF during the bread loading
  • The cast iron never achieved the 500 dF of the oven during preheat.

Since the granite-ware has much less thermal mass, losing 85 dF isn't unreasonable during the few minutes (or seconds) needed to load the loaves. But, the cast iron has so much thermal mass, that a 100 dF loss of heat seems to be a bit much.

DanAyo's picture
DanAyo

I didn’t run data during the pre-heat, but I did get this data.

”These temperatures were taken just before the dough was loaded. Stone - 529, floor of oven - 568, CIC - 504, GW - 512.”

Both units always slightly exceeded 500F initially. After the cold dough was placed in each vessel they never recovered to 500F.

Dan

Texas Baker said, “But, the cast iron has so much thermal mass, that a 100 dF loss of heat seems to be a bit much.” I thought that also, but it is what it is :)

texasbakerdad's picture
texasbakerdad

Wow... It take so long for me heat up my cast iron, I am surprised it cooled so quickly. When you were taking the 'out of the oven' measurements, what were the vessels sitting on? Glass, metal, oven mittens? How did you take the out of the oven measurements? With the fireboard probes? Or an infrared temperature gun?

Thanks!

I'd love to due the same detailed experiment on clay pots. Maybe they hold heat a lot better.

texasbakerdad's picture
texasbakerdad

There are two uses for the cast iron with lid.

  1. Trap in moisture
  2. Properly cook the bottom of the loaf

If you can solve #2 with a pizza stone, then, the thermal mass property of cast iron isn't as important. If we only need to solve #1, I think the granite-ware makes a lot more sense (or any thin metal, non-deforming, and oven safe cover).

barryvabeach's picture
barryvabeach

Dan, nice work, and thanks for the post.  Several questions,  first , what differences did you observe in the loaves when they were baked? 

Any difference in oven spring, crumb structure, thickness of crust?

While I love hard data, there have been a number of people who have baked identical loaves in a cold dutch oven and a preheated dutch oven, so not sure if the temperature in the DO is a critical factor.  My completely uneducated guess is that the best results will be obtained when the volume of the container or cover is a very slight bit larger than the size of the risen loaf, since the smaller the area, the more moist the environment.  The second consideration is how well the cover or container does in trapping moisture.  The configuration of a cast iron combo cooker ( with a rim and a ledge that interlock) suggests that moisture will be trapped more effectively than with an upended cover, though I don't know if there has been any testing of that .  I think that the probes probably negatively impacted the retention of moisture in both the CI and GW.

 Second, I read where you preheated the cast iron for 1 1/2 hours - how long do you think it was out of the oven for loading?  I am surprised it dropped 100 degrees.  Once it got down to 400, not surprised with all that mass that it did not recover much in the next 20 minutes.  Again, thanks for the results, and keep up the testing.

DanAyo's picture
DanAyo

Barry, the purpose of the test was to determine the ambient temperature in each vessel at 30 second intervals during the time spent in the oven.  Both loaves where sacrificed for the test. Probes where pushed through the bottom of each loaf so that they would be supported and at the same time have their tips exposed to the air inside the vessel.

The GW cover and also the CIC was removed from the heat for maybe a mnute. I worked as fast as I could. TAfter the probes where positioned in each dough they was placed on parchment to speed the loading times.

trailrunner's picture
trailrunner

there is no need to use anything but the complete GW to bake the bread. There is NO need for thermal mass aka a stone of any kind. There is NO need for any preheat other than setting the empty GW roaster in the oven when you first start the preheat and when your oven signifies preheat is complete the GW is ready. 

As Danny notes GW heats up, cools, reheats extremely quickly. You remove your GW roaster from the 500 degree oven , place your loaf/ loaves( i have a really large one that holds 2 -750g loaves side by side) inside replace top set back in 500 degree oven for 10-15 min then remove top and complete bake at 450-475 for 25 min. That’s it. It isn’t rocket science. It’s simple . 

I cant defend this but all the CI is excessive overkill . Unneeded. Even Danny’s trial is more than needed. The bottoms of my breads are perfect. No stone needed. Since i baked my first loaves in 1974 i will say i have had few enough failures i can count them on one hand. 

Hope Danny’s and my testamonials will assist those interested bakers. CI has its place but this isnt one of them for efficient quality SD baking. 

texasbakerdad's picture
texasbakerdad

Ok, I believe you, and I am still skeptical. Why? Because I have read at least 4 books and 20 internet articles that recommend a pizza stone. And, my pizzas need them. But... pizza are not sour dough loaves, pizzas have sauce and oily cheese, and thus, the stone almost certainly plays a bigger role. 

Maybe the stone is more important for weaker ovens that have a hard time replacing lost heat introduced by new foods and open oven doors? Some electric ovens really struggle to replace lost heat when running at 450 dF. I know, because I had one and had to get rid of it. 

I'm not ready to unequivocally renounce the benefits of cast iron baking and pizza stones, but you both make a compelling case for me to challenge my previously held conclusions. 

thanks!

DanAyo's picture
DanAyo

I never got the fact that you bake with your GW alone without a stone. Before testing GW, I would have blown that off as heresy ;-) But after my Granite Ware conversion <Hallelujah> I’ve learned to listen. It is a human characteristic to hold dear and defend our beliefs. The thought of being wrong is uncomfortable, and at times, worse. But I’d rather be humbled and accept correction, than to continue to hold and operate according to errany information. “the truth will set you free” :D

Question - the bottom of my roaster has a pattern stamped into the bottom. Do you bake on the uneven surface? I thought about a peice of relatively light aluminum plate cut to measure.

Is this the UNIT you use? 

I also like this UNIT . I haven’t tried it, but it might be great for single loaves.

Danny

 

trailrunner's picture
trailrunner

I have posted pics of mine in some of my bakes so you can look back. My GW were my Mom's from the 1940's. Still cook like new. Mine have a smooth bottom. My large one has a removable insert for lifting out the roast. It is super convenient to lift it out and place the loaves on parchment in it and set it back in the roaster and put the lid on and that's that.

Not sure where the fear of the " hot pan" vs using a super hot pizza stone that you have to try and get the rack in your oven pulled out and remove the hot covering pan and then recover the stone with the hot pan.And slide it all back in . Too much work and bending over the oven. 

The combo cooker is OK but I don't want the cast iron. I have plenty of it from my Mom and grandmother and it definitely has its place. 

Look forward to other posts and results. Good Luck. 

dabrownman's picture
dabrownman

because it is lightweight much safer and easier to handle and all you really want is to trap the water vapor.  If you don't have a stone than any DO is better.  My aluminum Magnaware DO is the best since ui reheats so much faster than the Combo Cooker but the combo cook is way easier to load and unload and much much safer.

trailrunner's picture
trailrunner

From July 2016-July 2017 all i had was a very old Kenmore gas oven. Prior to that i had the very top of the line  Miele electric convection ovens ( double ovens) from 2007-2016. Since Nov 2017-present i have a really cheap Kenmore electric. 

Wanna look at pics on my page? All baked in GW. No stones... dont have one. CI?? Retired to basement. Let the books and hard sell go... really. I’m not selling cookbooks or pots. Ease of baking great bread.. that’s it. 

dabrownman's picture
dabrownman

then that is a DO right?  I get then at Goodwill for  a buck on Dollar Thursday's and they are as good as any other DO too!

DanAyo's picture
DanAyo

I never thought like that, but I guess the Granite Ware (top & bottom) would be considered a light weight Dutch Oven. Good Observation. 

Dan

DanAyo's picture
DanAyo

The giant plus for Granite Ware is the super light weight. It recovers heat much faster than cast iron and at the same time seals in the steam.

I often use the GW for a cover over the baking stone, but using the GE top and bottom also dose a great job.

The weight is the big issue.

Dan

gerryp123's picture
gerryp123

Interesting testing and observations.

I've used both DO and GW lid over quarry-tile,  and (for me) the DO gives better, more consistent results in terms of crust thickness and oven spring. 

Have never used the full GW as a DO. I thought it would be important that the "steam-container" be only slightly larger than the loaf to keep steam in close proximity to the loaf during the first few critical minutes of the bake.  I have used large and small DO for the same size loaf, and the result proved this point (to me).  I would have thought a GW DO would be too large for a single loaf.

MTloaf's picture
MTloaf

I have a rectangular graniteware roasting pan that I use on a stone. My method involves rinsing the inside of the pan with water before placing it over the loaf with a couple of ice cubes on the stone. I get blisters every time, which I happen to like and it tells me that there is plenty of steam. It also fits over my pullman pan w/o lid so I can steam it as well. It is much easier and better than all the other methods I have tried. Thanks for the data that confirms my observations. Photo of this morning's bake.

DanAyo's picture
DanAyo

Are you rinsing a cold graniteware or is it preheated?

MTloaf's picture
MTloaf

I am rinsing a cold graniteware pan and then placing it over the loaf in the oven.

 

berryblondeboys's picture
berryblondeboys

This is great information and great timing as I was just looking recently about cloches and saw a slew of posts about different thoughts on what makes a good cloche. I own a large le Creuset dutch oven and I use it A LOT in winter months. Will it get harmed if I use it for a cloch? I'm afraid of damaging the enamel as it is a go-to pan for many things (that and a smaller one).

I also have a large pan that I bought probably 20 years ago that you can use either the top or bottom. It's a heavy gauge stainless steel and I use that every year for sarma. First to cook/stew it, and then just the lid to crisp up the topping.

My main dilemma is that I always either make one LARGE loaf that is about 18" diameter. Or, I make two smaller loaves so that I don't have to bake so often, so having TWO cloches is ideal for me or one that is big enough for two loaves to fit under.

Let me take photos of what I have and then I'll post again. ETA I took photos, but, measurements are what are really needed. The pan's interior measurements are just shy of 15" by just shy of 12" inches. If I count lip to lip, it's 15-12". and it's 12" deep. There's no label/mark, so I have no idea who made it. I'm not even sure what city I bought it in! Could have been Philadelphia, Waterloo, ON or Chicago, IL. One of those places I lived long ago. LOL


Donald Miller's picture
Donald Miller

The dish is looking so yummy..