The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Granite Baking Stone

ksimmons's picture

Granite Baking Stone

Could a granite sink cut-out be used for a baking stone, safely?Seems likely to break or even explode. Sure don't want to blow the glass out of my new oven door.What say U?

Salilah's picture

Not sure.  I've used a 3/4cm thick granite stone (from Tesco, sold as a surface protector, with feet cut off) - and both have cracked down the middle after about a month of baking :-(  No explosion though, so I still use them cracked

clazar123's picture

I had seen a steak cooked on a granite slab (on youtube) before I got my granite countertops. I've had them 2 yrears and LOVE them.

This is an interesting link:

Granite won't explode but may crack. I would be interested in how the resin performs when heated (if it is treated with a resin sealer). The biggest drawback is the weight which can be it's biggest asset for using as a preheated mass in the oven.

Chuck's picture

"Granite" covers a wide variety of stone, some of which work fine for baking stones and some of which don't. So it's not possible to say either "granite sink cutouts always make good baking stones" or "granite sink cutouts never make good baking stones".

If it's low porosity granite (often but not always dark colored) and raw, it will work fine for a baking stone. But if it's high porosity granite (i.e. absorbs away "spills"), it's not a good idea for a baking stone. If it's "sealed" with a natural sealer like beeswax, it's probably okay, except there probably wouldn't have been any reason to seal it unless it was high porosity which case it won't make a good baking stone unless the sealer can stand up to oven temperatures. If it's "sealed" with some chemical you can't pronounce, it's obviously food-safe at room temperature, but the thought of being the guinea-pig to find out if that sealer remains food-safe at oven temperature is a bit scary.

The smooth polished surface that most granite countertops have that's important for counter use doesn't matter for use as a baking stone. It probably won't hurt anything  ...but it won't help anything either. If the bottom side of the sink cutout is rough-but-not-too-rough, you may want to turn it over to use it as a baking stone.

Also, contractors sometimes try to be helpful by putting small rubber feet on the four corners of the bottom of a sink cutout that's being saved. Those feet will probably turn into icky-sticky goo at oven temperatures. So it's best if the contractors do not do this. If they do it anyway before you can communicate with them, scrape those feet back off before using it as a baking stone.

HMerlitti's picture

I have a 1" granite slab in my oven.   I bring the oven to 550 F  and bake bread.

I picked the slab on of a discard bin in the back of a company that put granite in kitchens.   I had the stone cut to size.

What else can I tell you ??

ksimmons's picture

Thanks to all the above who responded to my question.

 I live in Alaska and it seems impossible to find unglazed quarry tile here.I really wanted something thicker, more mass,so I considered granite as a possibility. I'll check with a local granite dealer and see what I can learn.

 Home Depot and Lowes sell 18"x18" glazed ceramic tiles that could be cut to fit my oven perfectly.However, some have warned of possible toxic off gassing of the glaze. I'm not sure this would be a problem as the tiles were fired at a much higher temp during manufacturing than it would ever get in my oven. In other words, I don't think the glaze would break down. (not sure though) Even if it did, could the problem be averted by using parchment paper?

Chuck's picture

... glazed ceramic tiles that could be cut to fit my oven...

Do not do this. Many of the more colorful glazes contain lead that can leach out even at low temperatures. (The problem being high temperatures is misinformation that can lead to a mis-conclusion.) In my experience low-level chronic illnesses are really the pits and definitely to be avoided.

The classic example is a pitcher routinely used for the breakfast orange juice that made an entire family chronically ill (the slightly acidic orange juice leached out the lead at a faster than usual rate). Glazes containing lead have been "illegal" to produce in the U.S. for many years now  ...but that restriction doesn't always apply to pottery made in other countries and imported. There's no simple, surefire way to tell which glazes contain lead. So the only reasonable way to protect yourself is to just not use glazed ceramics that don't specifically say "food-safe" for cooking at all.

PeterS's picture

that lead, if present, is going to leach out of a tile used for baking bread in an oven. Your comparison to orange juice in a pitcher is literally apples and oranges ;) The bread is not acidic enough nor are the conditions conducive to leaching. Lead if present in a tile would be considered bio-unavailable during baking. A compromising factor would be if a tile cracked and or dusted allowing particulates to get into the bread--and in large quantities at that.

There has been a lot of discussion about this on these forums and elsewhere, the hazard has been greatly overstated; porcelain tiles are just fine for baking bread.



thomaschacon's picture
thomaschacon (not verified)

You're on a roll, tonight, Peter? BPA is of no concern? So it lead leaching?

There is definitely a school-of-thought in both industrial and hobby ceramics that the 'leaching glaze' issue is totally overblown. Thus, if there is pottery leaching harmful compounds into food and drink, it is being produced both by companies and people that do not know any better and who have made a conscious choice to ignore the issue. The US FDA (Food and Drug Administration) tests ceramic ware extensively for leaching metals often with distressing results. (aside: There's that FDA again!) After a meeting and lunch with their representative at the American Ceramic Society convention I was very encouraged by their position on this matter. While they are ready to take action against offenders, they are much more anxious to see initiatives by companies and potters to learn how to recognize leach-likely processes, materials, and formulations and learn how to fix the problems. There are lots of things we don't know about leaching in glazes. However what follows are some things we do know. Glazes are glass and we tend to think of them as timeless, indestructible. However all glass leaches to some extent when it comes into contact with even water. With acids, especially if the contact occurs over a period of time or the acid is hot, the effect is obviously greater. Vandals, for example, simply use sulfuric acid in bingo doppers to etch grafitti into windows. This is evident by a change in the gloss and texture of the glass surface over time. Glaze color can change also. As a demonstration try 33% CaO, 42% B2O3, 6% Al2O3 & 18% SiO2 at 950C. It should fizz and dissolve in vinegar within minutes even though it fires to a clear and apparently hard surface. If a glaze is made from harmless materials like silica, dolomite, kaolin, feldspar, whiting, ball clay, etc. leaching is only a functional and aesthetic issue. But if the glaze employs metallic colorants (other than iron) or other minerals containing lithium, barium, lead, chrome, etc. then safety and legal liability becomes a concern. The likelihood of leaching is not just a matter of whether the ingredients used to make a glaze are dangerous. The issue is complex, involving the ways in which the materials are prepared and fired and the formulations that are used. It is possible to use toxic materials safely and it is possible to compromise an otherwise safe glaze by unbalanced mixtures. If a customer claims injury from leaching of your ware you have to demonstrate that there was no reason for you to have been concerned about the hazard and that you were diligent in researching the subject. If you don't know how to appraise a glaze's safety then play it safe. For example, there are ways to use barium safely but if you don't know them then don't use barium on food surfaces.

lumos's picture

I've been using granite chopping board like this (the photo not mine) for a few years before I got cordierite kiln shelf cut to fit my oven without any problem. It's 2cm thick, not expensive, safe (surface only polished, not glazed)  and you can buy it in many places that sells kitchen least in UK where I am.

The new cordierite kiln shelves are actually exactly the same size as the granite board I'd been using, but it's stronger against thermal shock and can be cut to fit to your oven size, if the chopping board is not a good size for you. Look for pottery kiln manufacturer in you area and ask them if they can make one for you.  Shouldn't be too expensive. (Mine was about the same price as the chopping board)



Susan Kline's picture
Susan Kline

I left my baking stone in the oven and spills baked on.  I scrubbed it, but it still remains stained.  Does anyone have any ideas on how to restore it?  I thought of sanding it, but I don't know if I might be releasing some unwanted hazards under the surface.  It has a rough surface and came from The Pampered Chef. 

booch221's picture

It is natural for baking stones to change color and darken over time. That's what the directions that came with my stone said.

My sister-in-law has one that's now completely black, like a well seasoned cast iron skillet.

My advice is to leave it alone. As long as it bakes OK, don't worry about the appearance.

dwcoleman's picture

I have a fibrament that I can leave in for the oven clean cycle, it works amazing.

If you're hesitant to try it, you could use water/baking soda as a mild abrasive.

Susan Kline's picture
Susan Kline

Thanks for both of the responses to my baking stone.  I will be happy to start using it again.