That's some serious recipe testing. Thanks for sharing your results! I've been cooking for years, yet I'm constantly surprised by how much I still don't know.

Blissful Baker, I've been meaning to post a follow up . . thanks for the nudge. I checked my baking powder (non-aluminum) which I bought in early December and it has an August 2012 expiration so I did not replace it. I bought new cornmeal, even though I'd refrigerated the stuff I had and tasted it, and used 1/3 coarse yellow to 2/3 medium white. I wanted some texture and color, and that ratio worked. The double corn bread turned out fabulous, with no bitterness, when baked in a well-buttered skillet. The warm custard "spoon bread" was marginally better, but still had the chemical taste. I reduced the baking powder back to the one teaspoon called for in the JOC recipe and it tasted much better. I did more research on chemical leavening agents, because I use a lot of buttermilk in my cooking, which is highly acidic. The sources I found advise you to be careful when adapting recipes using baking soda or baking powder (which contains baking soda), for this reason. I suspect that it was actually the baking soda in the baking powder that caused the problem, as the amount of baking soda given the amount of buttermilk in the winning warm custard spoon bread is twice the recommended amount. I made another batch of the warm custard spoon bread, just out of curiosity, to see if adding back in the sugar (while using only one teaspoon of baking powder) would make a difference and it does. It doesn't make the dish sweet, but it does bring out the other flavors in the dish. So, I'm back to the original JOC recipe, with vanilla and nutmeg added. And, following the recommendation of The Joy of Cooking, I found it even better with butter, maple syrup and bacon.Thanks, everyone!!

Antonia, did you ever find out what the problem was? Based on this thread, I switched to aluminum-free baking powder myself. Thanks for vicarious tip!

If you had the same problem with two different recipes using the same baking powder, I'd have to call it the baking powder. I have never used aluminum free BP, but will my next bread or cake project that calls for it, as that's what I just bought to replace an almost-empty can. I'd think the freshness might be an issue, too; many cooks like me use the same can/box of baking powder for a LONG time, because we don't use it all that often and of course, when we do, it's in small amounts. As a precaution, I'm going to try using a smaller amount when I open this can this weekend.

I made crock pot chili for dinner and asked my daughter-in-law to make Merrill's double-corn bread, but she omitted the thyme and added crushed cumin. They ate earlier and said it was wonderful. I just got home from work and they kindly left a sliver and some crumbs for me. It was fine. I dunno. . .I'm still leaning toward the too-much leavener theory.

I make cornbread the traditional Abruzzo way - cornmeal, hot water and a pinch of salt.

Is your cornmeal course? Sometimes I find that the courser the meal, the more likely there is a chalky after sensation to it---leaving a sensation similar to eating spinach (I hope I am not the only one who experiences this!) Anyway, sometimes that effects the taste for me. I have a superb recipe, a no fail. LMK if you'd like to try it and see if it still happens. Also...I prefer white corn meal, which isn't to say that I don't use yellow.

Amazingly, as I'm reading this I'm eating Merrill's 2 corn cornbread that I made a couple days ago. Mine isn't bitter at all. Is it possible the salt was omitted? Salt balances bitterness. Was the iron skillet used for anything else recently like cooking greens? It sounds to me like you're covering all your bases, and the only other thing I can think of is the cornmeal can be a bit bitter without it being rancid. I say buy some fresh cornmeal and try the recipe again and see what happens. Or try a Pyrex casserole pan and see if that makes a difference.

Well, if I had finished reading the question, I would have seen that you have the "rancid" answer covered. Sorry!

Here's another possibility: If you are using a good whole grain cornmeal, not degerminated, it may have gone rancid, which could account for that taste. Be sure to store whole grains in a cool place, tightly closed.

In most recipes for quick breads, cakes, pancakes and the like, one teaspoon of baking powder per cup of dry ingredients is sufficient to obtain a nice rise. Sometimes, if buttermilk or sour cream is used, baking soda is used instead. And once in a while, both baking powder and baking soda are used to create lift. Those chemical reactions that cause you to get a rise out of something can also cause changes in color (ever had a green-tinged carrot cake?) and taste.

In recipes that call for both leaveners, I'm willing to bet that you can safely eliminate or reduce one or the other. With Merrill's recipe, try reducing the baking powder to 1 teaspoon; The remaining teaspoon of baking powder, along with the teaspoon of baking soda reacting with the acid in the creme fraiche, will create enough bubbles of carbon dioxide to lift the cornbread to double its size. Or eliminate the baking soda entirely and use the full amount of baking powder.

Rarely, a bitter or metallic taste is caused by the reaction of those chemicals and the fillings or appliances in your teeth. If your mouth ever feels like it contains a weak AAA battery, it sort of does. Go to your dentist and ask for your fillings to be changed so that they're all the same kind. A sister-in-law says this happened to her. We hear the story every holiday at the buffet table.

Were there other acidic ingredients in the recipe such as buttermilk, yogurt, lemon juice or vinegar? It might be the the recipe proportions for acids are incorrect.

Check out the Uses section of this wikipedia article. http://en.wikipedia.org/wiki/Baking_powder

If there are other acidic ingredients it might be that you need to cut back on the baking powder and subsitute and equal amount of baking soda.

You may also be slightly more sensitive to bitter flavors than others.

I would suspect the baking soda - i find it has a tendency to be soapy and bitter....but this is a guess!