This from Tim Scarlett at Michigan Tech, who is coauthoring a brick identification guide for Left Coast Press, Inc. > > The indentation you describe is called a "frog" and it is indeed > caused by the molding process. Bricks with frogs are typically > "soft- > mud" manufactured, which means that very wet clay was slopped into a > > wooden or iron mold with four sides and a bottom. The bottom of the > > mold surface also included a raised area that impresses the clay when > > it is forced into the mold. The back of the mold is then "struck" > with a blade or wire. The strike creates the sixth side of a soft- > mud molded brick. You can often still see the strike marks on the > opposite side of the brick from the frog. If those strike marks are > > irregular, meaning that they appear to have been formed at non- > uniform angles, then the brick was probably hand struck while in the > > mold rather than by some automated process. > > The frog presents a couple of advantages- it creates a recess for > mortar, it makes each brick weigh just a little bit less, makes each > > brick a bit thinner so it fires more throughly, and it takes slightly > > less clay to make each brick. While the difference seems trivial for > > each brick, multiply the difference in weight and cost by the 10 or > 100 thousand bricks in a large building or the millions of bricks > made annually in a large yard, and you can see how the savings do > indeed accrue! > > The bad news is that this information does not necessarily yield a > simple probable date of manufacture. That is a much more complex > problem. > > You can find more information in Larry Gurcke's 1987 book, Bricks and > > Brickmaking: A Handbook for Historical Archaeology (Idaho). Keep an > > eye out for the second edition of this text from Left Coast Press, > updated and revised to include much more chronological and regional > information! > > Best, > Tim > > Timothy Scarlett > Assistant Professor of Archaeology > Industrial Heritage and Archaeology > Department of Social Sciences > Michigan Technological University > [log in to unmask] > (906)487-2359 > (906)487-2468 > ------------------------ > Currently conducting fieldwork at the site of the West Point Foundry > > in Cold Spring, New York. > > > Mitch Allen Publisher Left Coast Press, Inc. 1630 N. Main Street, #400 Walnut Creek, California 94596 925 935-3380 phone and fax [log in to unmask] www.LCoastPress.com ========================================================= Important Subscriber Information: The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes). If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).