The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Oven Temperature: Surface or Air?

Brizo's picture
Brizo

Oven Temperature: Surface or Air?

Hello, I'm very new to bread making and baking in general. 

I've noticed the air in the oven and the surface temperature of the metal baking pan are very different, eg the air might be 190C but the surface of the pan will be 220C.

Which is the better reference to use so that I know my oven is at the right temperature or not.  In this case I'm making baguettes.

I use an IR gun for the surface temp of the pan and an oven thermometer hanging from the shelf for the air temp.

Jay Keith's picture
Jay Keith

The air temperature. That's what the bread is being subjected to.

Brizo's picture
Brizo

Is it not also being subjected to the heat of the pan its sitting on?

 

buck upson's picture
buck upson

Found the same condition in my oven.  After thinking about, purchased a fancy high AIR temp thermometer for $50.

1st step was to do the KAF "cook toast" with 12 slices of bread laid out over two oven racks to see variations.

Found out my very expensive Electric oven  (over $2,000) has temperature swings of over 50 degrees F when set for 350F.  Now use convection bake and still see uneven swings. The low swing is 320F & the High is 370F.

Wondering now if new similar priced KitchenAid or GE oven control temps any better??

Doc.Dough's picture
Doc.Dough

See: http://bit.ly/2PGyPbB for a short tutorial on heat transfer in bread ovens.

I find the temperature swings to be interesting. The balanced temperatures you report for a convection oven seems to reflect that the thermostat set point is in fact very close to the average oven temperature, but the ±25°F seems relatively high, given the simplicity (low cost) and wide availability of PID controllers.  My combi oven (a 2003 model from Rational/HennyPenny) holds within a few degrees of the set point over the specified temperature range (85-575°F) so other than the prioritization of profit over performance I see no reason for any modern design to float ±25°F.  For accurate and timely temperature monitoring, some inexpensive digital volt/ohm meters come with a short Type K welded bead thermocouple and a mode that allows you to read it easily.  You should be able to hold it in place in the oven with a paper clip.  Accuracy should be ±0.2°C.

Jay Keith's picture
Jay Keith

so, ultimately, that's the temperature at which you're baking the bread, as that's what's measured to give you the oven temperature.

A probe thermometer in the loaf is also useful, of course, to let you know when the loaf is baked.

old baker's picture
old baker

Apologies to all for the mostly blank post.  My response is at the bottom.  Don't know what happened and I can't edit/correct it.

Doc.Dough's picture
Doc.Dough

It turns out that it is not just the air temperature that the dough sees (except in the case of a commercial convection oven).  Look here: Heat Transfer Mechanisms in a Home Oven for a tutorial.  No pictures!!

Doc.Dough's picture
Doc.Dough

reading is based on the assumption that the surface you are pointing it at has an IR emissivity of 0.9.  The emissivity of the shiny side of aluminum foil is about 0.05 and a black cast iron pan is about 0.8.  When you try to read the temperature of food covered with foil, you wind up reading the temperature of whatever background object the foil is reflecting at your thermometer (on the counter is may be the wall or a window, while in the oven it may be the oven wall).  Try reading the temperature of boiling water in a shiny stainless pan (the water will be close to 100°C but will read lower) and then check the apparent temperature of the outside (depending on the specifics it may read 65-85°C).  

BobBoule's picture
BobBoule

to try and use an IR thermometer on pans, I have tried for years. I have had very consistent results using a good quality (air) thermometer for many years. Each pan will read differently depending on what it's made of and the characteristics of its surface. In addition to the standard one thermometer I use, I will meticulously document which vessel or sheet I use to bake on since each one changes the bake time (and sometimes bake quality) for each recipe. Consistency is King.

albacore's picture
albacore

I wouldn't trust the readings of a thermometer that actually sits inside the oven - it's a hostile environment!

The best way to measure your oven temperature with any accuracy is with a thermocouple thermometer and bead thermocouple. The thermocouple needs to have glassfibre insulated leads and a welded tip (cheap ones tend to be soldered, which melts).

Attach the bead to some fixed object in the oven near where the bread will be and pass the wire through the gap in the oven door where the seal contacts it.

Inexpensive kit these days, but you probably wouldn't want to buy it just for this job.

Lance