Sweet Cement

By Robert L. Wolke
Wednesday, September 14, 2005

What is the strongest edible adhesive that will work on gingerbread? I'm thinking this Christmas I might use it for making a gingerbread house. And how cohesive is gingerbread, because it might break easily?

-- Nathan, age 12

Don't worry, Nathan. Gingerbread houses rarely have to withstand earthquakes, so a moderately strong adhesive will do.

Of course, the odds are pretty slim that a gingerbread house will actually be eaten -- by humans, that is. (If you keep your masterpiece from year to year, store it in mouse-proof packaging.) So when it comes right down to it, your glue doesn't have to be edible. Nevertheless, it's simply good practice when making something out of food to use only edible components, so your edibility concern is quite appropriate.

The best cement for such a construction project is known as royal icing. It's not only edible, but it also dries rock-hard. Here's how to make it: In a medium bowl, mix 2 1/3 cups confectioners' sugar,

1/2 teaspoon cream of tartar, 2 egg whites (their albumin proteins are the actual glue) and 3/4 teaspoon vanilla extract, only because we both know you're going to lick the bowl. Beat the mixture with an electric hand mixer until it is thoroughly combined. If it's not a nice, thick paste, thicken it with a bit more sugar or thin it with water a drop at a time. You can color it with food coloring, if you wish. It will keep for several days in the bowl (no need to refrigerate it) if covered with a damp cloth.

Regarding the gingerbread panels themselves, just be sure to make them from a relatively dense dough, rolled out to a uniform thickness. Your house will be sturdy enough to withstand the Big Bad Wolf's most powerful huffs and puffs.

In baking bread, is it safe to use unglazed stone or clay tiles, such as one would find at any Home Depot, in place of the baking stones sold in kitchen stores? Could such tiles allow harmful elements or compounds to leach into the food that is baked atop it? The cost differential favors -- in some cases, greatly favors -- the tile, but I don't want my frugality to come at the expense of food safety.

Unglazed quarry tiles, the dark red, 6-by-6-inch flooring squares sold at home improvement stores for about $1.20 per square foot, are made by extruding natural clays or crushed shale into half-inch sheets and firing them at temperatures as high as 2,000 degrees. Because they are made from natural materials, their chemical compositions will vary, including the possibility that compounds of toxic metals such as arsenic or lead might be present. That's of no concern to the flooring manufacturers, but the tiles might not be entirely safe for contact with food.

The word "unglazed" is critical, by the way, because glazes -- smooth glassy coatings, especially the yellow ones -- often contain lead.

There's no doubt that quarry tiles will work well to help bake breads and pizzas develop a crisp crust. During my unsuccessful efforts to produce a good, French sourdough baguette, my oven rack was covered with them. Although I am obviously still alive, I cannot draw any general conclusions about the safety of the tiles. However, lead poisoning is cumulative, and one of its major symptoms is a lowering of IQ. Have my columns been getting more and more dimwitted?

When I received this question, I ran out to Home Depot, bought one quarry tile and checked its surface with a sensitive test for lead. The test was negative; no lead.

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