Baking Pan Patterns

kuahji

So a friend of mine baked some cookies, then noticed some patterns on the baking pan. The person asked me what caused these patterns, or even if they are just random... any ideas?

http://imageshack.us/photo/my-images...532442373.jpg/

Evo

From the oils and other ingredients in the cookies.

QuarkCharmer

Hmm, I'll take a blind guess.

Ever notice how cookies are not consistent and have natural ridges because the dough is not homogeneous?

http://aimfundraising.com/images/home-cookiedough.jpg

Perhaps this pattern is the result of oil dropping down through the crevices of the cookie and then spreading out into circles, but the edges are stopped from spreading by their tension (when it reaches the outside edge of the cookie) and the walls formed under the cookie due to the ridges and non homogeneous dough.

You could probably test this by over mixing a cookie dough that contains no other particulates and then forming it into a cookie shape with a uniform bottom. Then you could maybe use a tooth pick to carve patterns into the bottoms of some of them and see if the patterns that emerge on the steel are halted by the lines. On some cookies you could perhaps put a toothpick hole straight through it and widen the top of the cookie so it slopes towards the hole at any point. I think the oil would come up and make it's way to the hole and cause a nice big shiny circular brushed metal looking thing right under it.

Hepth

Yeah, reminds me of metallic grain growth. Its most likely random nucleation points of oil from the cookie, they spread out from their nucleation point until they hit each other, this causes grain boundaries, but the oil is looking to disperse so there is tension at the grain boundries.

I love when something I have done research on (2 published papers, abnormal sub-grain growth) applies to everyday life; I even have my old F77 code that could simulate this... a new paper?

QuarkCharmer

Cookie research? Good luck funding that.

Astronuc

The variation in the metal (silver, grey or white) is due to grain orientation, which is somewhat random. The brown coloration would seem to be from organic material, oil or cookie dough.

Hepth

Are you sure about the grain orientation statement? I assume this is some aluminum alloy baking sheet, there's no way the grain size is on the order of centimeters, right?

edit: unless due to constant baking it is repeated being annealed and so much energy is in the system grain boundaries constantly migrate and the ones you see left are the ones where the misorientation(sic) between the two regions are maximal. (in terms of boundary energy)