# The eternal aluminium foil question

Dear Cecil

I read with great interest your synopsis of the shiny side in, shiny side out debate as this has always been a subject of contention between myself and my peers. Another related question: As a heroin user for seven years (eight years clean) I used to smoke the stuff on aluminium foil. My fellow users advised me to use the dull side as the shiny side was more likely to release carcinogens during the smoking process. Of course, absurdly, carcinogens were the least of my problems. Your potato cooking enquiries have cleared up that the difference between the two sides in terms of chemicals is at best marginal. My question is this: Does aluminium foil relese carcinogens or other harmfull chemicals during the heating up process? When will I die?

I am not commenting on the heroin question but just on the potato question and the technique Cecil used to test the question. As any elementary school physics student knows, the shiny side reflects better than the dull side and there will better reflect heat emerging from the potato in the form of infrared waves. However, what difference will this make if you are bathing the entire potatoes in air of 450 degrees? None, I would think. Although you did not give us any data points regarding the respective potatoes temperatures as a function of time, I presume that one increased in temperature more slowly than the other in each case, a lag that was surely do to different water content. You should have weighed the potatoes in addition to determining their volume. (Actually, you should have determined their volumes by lowering each into water contained in a graduated cylinder (or Pyrex measuring cup; you know the kind). Finally, the test you want to do is to not use a convection oven but rather a means of heating the potatoes directly, such as in a microwave over. Unfortunately, the aluminum jacket would foil that plan.

Welcome to the Straight Dope. A link to the column you’re commenting on is appreciated. Providing one can be as simple as pasting the URL into your post. Like so: http://www.straightdope.com/classics/a5_172.html

Thanks for the reminder. I will do as suggested in the future.

http://www.straightdope.com/classics/a5_172.html

And if you use the url and /url tags (enclose them in brackets), you can have the link read as anything you want, rather than the ugly internet address. Thus, Should a baking potato be wrapped in foil shiny side in or shiny side out?

I only smoke heroin in certified borosilicate glass. I just don’t trust all those additives they put into metal alloys.

As for aluminium, it is generally considered to be non-toxic and not highly biologically reactive, but if inhaled in fine particulate form it can be toxic. It will basically sit in for calcium in the body in high concentrations, and it will affect the central nervous system by changing ion potentials (again, in high concentrations). Generally the only way you will see these kinds of concentrations is from inhaling burning aluminium. Ironically, the aluminium armor and major structure of the M2/M3 Bradley Fighting Vehicle was found to create a toxic smoke when vaporized or on fire (although incidents of actual fire in combat have been found to be less than originally feared).

Did your aluminium peace pipe give you some unhealties? Probably not too much, since the heat is not enough to catch the foil on fire. Aluminium residue from non-acidic foods is minimal, although you want to avoid cooking high acid foods in aluminium for obvious reasons.

Stranger

I’m assuming that “foil that plan” was pun intended? If so, then: hehe.

Jim, after that long clean and it still hasn’t killed you I, though I am nothing like a doctor and prefer pulling bad advice outta my ass, would suggest you stop worrying about it. The connection between aluminum and Alzheimer’s has been debunked so it appears you are free to enjoy your life.

Edited to add: If you found the information you acquired here usable please consider subscribing. If not, you have 30 days to argue and I’ll STILL suggest a well-spoken gent such as yourself subscribe. Nothing personal.

I would wager that the people really in the know on this topic are foodservice professionals (such as myself) who have baked a metric buttload of potatoes over the years. Include also those who manufacture materials specifically for the foodservice industry.

One of those “materials” is … wait for it … “potato wrap”. This is aluminum foil that comes in sheets specifically sized for wrapping a typical potato for baking. It is often gold on one side, and the gold side is supposed to be on the outside. The “inside” of these sheets happens to be the dull side. It would seem that if there was any credence to the idea that potatoes cook faster/better with the shiny side in, then all these chefs and potato wrap manufacturers would have figured it out by now and changed their ways.

In any case, the point of wrapping the potato is to retain moisture and avoid a crispy skin, not to make it cook faster (though retaining moisture in and of itself helps to speed cooking) and the shininess of the foil has no effect whatsoever on moisture retention.

I would also like to add that 450 degrees is way too hot for baking potatoes (or baking much of anything, really. Except pizza.). 350 is much better all around.