February 14, 2005

Referring to "dumb" irons: They are so called because they are not hardened and therefore do not "ring" when struck. Their primary purpose is to open up a seam which has not been properly made i.e. too tight a caulking seam. Not being hardened, they do not bite into the seam and so are easily removed - try with an "0" or "1" and you'll damage the seam and then not get your iron out (without a struggle). The corollary is: You can neither thread nor drive caulking with a dumb iron.

Another use is to wedge the off side of a plank being caulked against the next one to it. This keeps the first from creeping during the caulking process (or when you stop for the night) in order to maintain an even, esthetically pleasing appearance. This can be an important consideration, especially when caulking the deck of a yacht. Hence the alternative name, "deck" iron!

If you leave the last seam threaded but not driven home the same result is achieved; but, the caulking can absorb moisture from morning dew (if the boat is outside) and then is more difficult to drive the next day. However, most caulkers use wooden wedges for this purpose - they're cheap and nobody steals them.