The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Do I need to treat/proof/season my new cordierite (kiln shelf) baking stone?

Bev619's picture

Do I need to treat/proof/season my new cordierite (kiln shelf) baking stone?

I managed to get a cordierite baking stone cut to size for $60 (includes shipping), but I'm not sure if I need to do anything with it before slapping my dough on it.  After hearing the Fibrament issue, not sure if I'm supposed to do anything special with mine.  It is actually from a clay/potters supply place so is actually meant for kiln shelving, so it is super heat resistent, but do I need to burn off any weird coatings?  Thanks!

mrfrost's picture

"Cordierite Baking Stones

Your new baking stone is made from cordierite, an FDA-approved industrial
refractory material used in commercial deck ovens. Our cordierite baking stones
will resist thermal shock (i.e., cracking when cold water hits a hot stone) to
temperatures in excess of 2300°F/1250°C, and possess both superior heat
conduction and heat retention properties. With the proper care and treatment,
your new stone will give you years, if not decades, of service.

To use and care for your NYB baking stone:


  1. Unwrap the stone and wipe it down with a damp cloth to remove any dust
    and loose cordierite particles.
  2. Place it in a cold oven and heat the stone to the oven's maximum tempera-
    ture, typically 500-550°F/260-290°C for 60-90 minutes and let
    it cool down. Your stone is now ready for baking.
  3. Over time, your stone will develop stains, to remove them, use a scraper to
    carefully dislodge any burned-on material and, if possible, run your stone
    through your oven's self-clean cycle, or hold at maximum temp for 1-2 hours.
  4. If necessary, rinse the stone with plain water to remove surface stains and
    debris. Neverunder any circumstances, use soap, detergent or oil on your
    , as they will soak into the cordierite and render it unfit for baking."

That said, I have their stone(nybakers), and not seeing these instructions(for whatever reason) I cured it similar to the way suggested for the Fibrament stone. Namely, I wiped it down, then put it in the oven and baked for one hour at 250degF, then for an hr at 350F...450...Finally 550. Then allowed it to cool.

Obviously overkill, maybe but happily baking 2 to 3 bread/pizza sessions a week for a little over a year.

Nickisafoodie's picture

Mrfrost, how thick are these stones?  And have you used fibrament ever?  If so how would you compare the two re performance and thickness?

I once had a 16" round stone the same color as shown in your link to NYBakers so I am thinking it was corderite.  It was about 5/8 inch thick, with parts of the bottom in the shape of a circle that were even thicker, a ring of sorts. It weighed about 12 pounds.  I used it regularly for 10 years at normal 500-550 degree oven temps.

Then I rigged my oven's self clean cycle per a Varasano type modification to the cleaning cycle for a 700 degree temp.  After five or so bakes at this temp the stone cracked. It shouldn't have cracked given the 2300 degree heat rating and there was no splashing or other human error type event that should have caused this.  I cared for it appropriately.  It was fine when I unloaded the last pizza, but the next morning when the oven was cold, I noticed a crack that effectively split in half. 

As a replacement I bought a fibrament which works well, but feels like cement to me and is thinner than the prior stone. But so far has worked at the high temps as above.

What I would really love is a 15"x20" corderite stone that was about 3/4" or even an inch thick which presumably would not be as at risk to crack.  A kiln shelf cut to size seems like the answer but not sure where to source something like this...  It seems to me the corderite and fibrament perform the same, so the issue is one of potential cracking/longevity...

mrfrost's picture

Mine is 16 x 16 x 5/8"(12.3 lbs.). I don't think NYB stocks that size any longer, but I do believe all of his stones are 5/8" thick. I really cannot comment about all brands of cordierite stones, but since they clearly state the capabilities of their stones(NYB), unless proven otherwise...

I have not heated mine above my ovens 550 degF capability, and like you, I think I would probably like a thicker stone for using at the ultra high temps(550+). There are drawbacks to a thicker, heavier stone however; moving among racks, removing from oven, etc. That should be considered, as it is not trivial, imo. I usually bake pizza on the lowest rack, breads on the next level up, so I often am shifting the stone around. While 12 lbs is seemingly not very heavy, the way one has to hold and maneuver the stone, out away from the body at times, puts considerable forces on the back and spine.

I will say that my oven has the exposed lower heating element, and when the stone is placed on the bottom rack, it is only a couple of inches away from the glowing hot element. I suspect the stone may get somewhat hotter than 550 before the temp sensor near the top of the oven registers such. Don't have an oven thermometer or laser to prove that though.

I agree that probably stones of varying types of material will perform the baking chores satisfactorily, and along with the longevity issue, cost is also a factor. I have read however, by someone who's opinion I respect(a seemingly scientific type, Mr November at, theoretically, cordierite probably is marginally superior to Fibrament in it's thermal properties. For whatever that's worth. I have never used Fibrament. Although not unreasonably priced, just a little higher than I'm willing to pay. Mine was $35 along with some other needed baking supplies(HG flour, malts, etc) on lasts years grand opening, free shipping offer($50 min).


carefreebaker's picture

I bought a brand new, never used baking stone at a church flea market for $4. It measures 16 1/2 x 14 1/2 and is 3/4" thick.

It is quite heavy. It is the same color as the one pictured in the above post.  It has a lip on the top and a lip on the bottom at opposite ends. I presume the top lip is for ease of baked good placement and removal and the bottom lip to guarantee no movement of the stone as the lip sits against the wire rack of oven.

Is there a way for me to tell if it is cordierite?

How long should I preheat a stone this thick?


Thank you


mrfrost's picture

Without being able to compare them side by side, one could only guess. And even then, unless they are labeled, or one is a materials expert...? In the end though, it really doesn't matter, as long as it is a baking stone(i.e., safe for food) and gets the job done.

Preheat time will just be a matter of experience, or "overkill", or trial and error. Some just generalize and say "a baking stone should be preheated for an hour", etc. Depending on the stone's thickness, oven type and set up, what one is baking, etc, maybe longer.

Mine is "only" 5/8" thick, and as you can see, positioned just above the exposed heating element. I only need to preheat for 30 minutes or so, even when baking a 5-6 minute pizza at 500º+. All things being equal, yours almost certainly would take a little longer to preheat.

You seem to have found a good bargain. Being that it is so thick, it is probably of good quality. Congratulations, and happy baking.

Bev619's picture

That's fabulous.  Thank you. 

Nickisafoodie's picture

Your points are spot on especially weight.  I actually have a soapstone that is 1 1/8" thick, must weigh close to 30 pounds.  A hassle on weight, but I could manage that.

At this thickness it takes way too long to heat (2 hours to get to 650° with cleaning cycle).  And three hours after the oven is off it is over 325° per my laser themometer - slow to heat and way slow to cool.  It would be perfect for an oven that was on all the time, or even a brick oven with strong thermal/heat storage properties used in commercial baking. 

I read of one 50 ton brick oven that given such high mass took 8 days to get to proper heat and once there, it was used 363 days a year!  And fired lightly on the two days of rest!  But for pizza or bread, soapstone IMHO is simply is not the best choice.

Thus back to Fibrament or Corderite- both of which should be fine at bread baking temps...

Tommy gram's picture
Tommy gram

Last I heard the way to go is not stone but a 1/4" thick piece of steel plate. The Iron Age people! Those stones crack up, no matter what they crack. The one I have now is in five pieces. I don't know about this Corderieite  but they seem awfully strict with their rules.