Ship Caulkers and Their Tools

This piece is an expanded version of an article written for the New Bedford Whaling Museum Blog

 The picture below shows a box of tools that belonged to an un-named ship caulker who doubtlessly worked with a crew of ship caulkers on the New Bedford waterfront sometime in the late 19th or early 20th century.  As with most tool boxes, we can tell something of the man who owned this set of tools, and what he did for a living.

 In the days of sail and Yankee whaling, ship caulkers were important shipyard workers, finishing the process of making new hulls and decks tight and leak-free; and restoring older hulls to the same the same degree of fitness prior to every extended whaling voyage.  Their job was one that required skill, but a fairly simple arsenal of tools.  These included caulking mallets of two or three types, a group of caulking “chisels” or “irons”, that were really tampers, and a small array of hooks or narrow scrapers to clean the seams between the hull or deck planks prior to caulking.  The actual caulking material could be comprised of cotton yarn or string, and most importantly, oakum, which was usually the yarn from which manila or hemp cordage was made, tarred with pitch.


                                                "Leather seat with wood sides and bottom. Contains one caulking mallet, five caulking irons,
                                                one seam raker made from a race knife, one instrument (seam raker), and one spare mallet handle."
                                               (New Bedford Whaling Museum)


The second picture shows men at work caulking and rigging the Bark Alice Knowles, getting her ready for an extended whaling voyage.


1991.50.2.27  -- Caulkers at side of Bark Alice Knowles. (New Bedford Whaling Museum)

 The first five men from the left of the picture are caulkers working on planks above the waterline on the bark.  The two men to the right appear to be riggers who are working at anchoring what are known as “chain plates”.  Chain plates are iron rods doubled back on each other that are fastened to the multiple port and starboard stays that support the various masts on the vessel.  These riggers are working on the chain plates that will anchor the port stays supporting the main mast.  There is a lot going on in this picture, but first, let’s go back to that caulker’s tool box.

 An obvious feature of this tool box is that it is fashioned as a seat, having a contoured leather top, with an opening that allows the tools to be accessed or stored as they are needed.  The opening also serves as a handle, so the caulker could easily carry the box from location to location on the job.  Ostensibly, the caulker could use his tool box as a seat while eating his lunch—but more importantly, he would use it as a seat when working on the bottom of a hull that had been hauled out of water, and was too close to the ground to allow him to stand comfortably (sometimes caulkers fixed “rocker bottoms” to their seat boxes, allowing them to rock backward when working overhead).  This feature suggests that the owner of this box likely worked on smaller vessels than large whalers.  The larger vessels were generally careened or “hove down” while afloat at the wharves so that their bottoms could be exposed for maintenance work.  The caulkers then worked from rafts alongside the vessels, and did not need to work from under the bottom.

 A second feature of this box is that the tools arrayed in front of it, are in nice condition.  The owner of them took care of them.  Many caulking tools, exposed as they are to salt water and the elements while working outside, are often rusted, pitted, with the ends of the irons peened from hard use.  These are not in that condition, because their owner cleaned and oiled them regularly.  The tools include five “caulking irons” of only two types.  Four of these (the pointed ones) are known as “clearing” or “reefing” irons.  There is little uniformity in the names of caulking irons, as regional and local names can dominate.  For instance, these reefing irons are also known as “jerry” or “cape” irons.  Whatever they may be called, they are seldom used as tampers to pound oakum into a seam, but rather are pounded with a mallet along the seam, with the point end forward, in order to clear the old caulking out of a seam before recaulking it.  The fifth caulking iron is known as a “double crease straight iron.”  It is the iron with the broad symmetrical foot.  This is a principal caulking iron—one that is used a lot.  “Double crease” means that the blunt edge of the iron is double the thickness of a “single crease” iron, and it usually is cupped in cross section.  This iron would be used on wider seams, or at the wide top of the seam at the surface.

 Another tool in this group, called a reefing hook or raker, also is used to clean out a seam, removing the loosened old caulking, freed up by the reefing iron.  This particular raker is really a different tool, called a “race” knife.  A race knife is a special knife that cuts a groove or “race” in a plank—either to delineate the waterline on a hull, or more usually to cut identifying marks in planks or barrel staves, so their relationship to their neighbors can be told when the hull or a barrel is assembled..  At any rate, a race knife makes a nice raker for a caulker.  Its presence here tells us that the owner of this kit of tools was not only fastidious about their condition, but he was also frugal, using a tool cast off from a former purpose, and converting it to his particular use.

The final tool of interest in this kit is a standard caulking mallet (and a spare handle for that mallet).  Caulking mallets are quite specialized hammers.  The head is made of wood, and usually is from 10 to 16 inches long, strengthened by iron bands that gird the head on either side of the eye for the handle, and again, near the ends or “faces”of the head.  The wood used for caulking mallets has to be extremely hard and durable.  The fanciest ones may be made of rosewood or ebony, but the usual working caulking mallets use live oak, black locust, or more usually, mesquite, as the wood of choice.  A particular feature, especially of many American caulking mallets, is a slot with blind ends, cut vertically through the head, between the iron bands on each side of the handle.  These slots, usually about 1/8 inch wide, can be 3 or 4 inches long, and sometimes are “stopped” at each end, with slightly larger holes bored by a drill or brace.  All of these features can be seen in the mallet belonging to the caulking kit.


A slightly different form of caulking mallet (what I think of as “English” pattern) eschews the inner metal rings, and instead has a larger inner diameter of the head, which is reinforced by two bolts passing through the thick diameter on either side of the handle hole.  These mallets may or may not have “tuning slits,” and are usually made of either lignum vitae or a dark tropical hardwood (not mesquite or black locust).  Here is a picture of such a mallet.  This one has tuning slits.


 The array of caulking irons in our caulker’s kit, with the majority being jerry irons, suggests that this caulker probably worked in a team of from 5 to 30 men, and his particular specialty was clearing the old caulking from a seam, and cleaning it out (with the seam rakers), so that the caulkers working behind him could concentrate on pounding new oakum into the cleaned seams.  These workers would have used a greater variety of caulking irons, including single and double crease straight irons, “bent” irons for working on seams at some reach away, especially in the seams of the “garboard” planks (which lie next to the keel,’ narrow “spike” and “trunnel” irons for caulking around the spike and trunnels that fastened the planks to the ship’s frame.  Also, instead of using a cast-off race knife to serve as a seam raker, specialized irons called “reefing hooks” were used for this purpose.  Examples of these sorts of caulking irons are shown below.  Most were available in narrow, medium and wide widths.  These are medium width ones.  The examples shown are in new condition are products of the Buffum Tool Co, which did business in Louisiana, Missouri.  This company supplied caulking (and other) tools for the shipbuilders of Gulf of Mexico and Mississippi River ports.


A –  double crease straight iron

B –  single crease straight iron

C – deck, or “dumb” iron.  Sharp edge—used for
       opening up a tight seam.

D –  reefing iron

E –  bent deck iron

F –  single crease bent iron

G – double crease bent iron

H – bent  trunnel or spike iron

I –   reef hook

J –  two small seam rakers


The penultimate step in the caulking of a ship’s hull was the final ramming home of the caulking in a seam, ensuring that it was tight, with no voids.  This was a two man operation, using a large straight caulking iron, loosely held in a handle held by one man, while a second swung a much larger mallet at the captive caulking iron  to slam the caulking home.  The handled caulking iron was known as a “hawsing” or “horsing” iron, and the large mallet a “hawsing mallet” or “beetle.”

The final step was to seal the seam with hot pitch (if below the waterline) or paint (such as white lead), if above.  The pitch was spread over the entire hull below the water line, and then this was covered by a sheathing of copper plates that functioned to defeat shipworms and encrusting barnacles.  The process of spreading the pitch was known as “paying” the hull.  In the days before copper sheathing (which was almost mandatory for whale ships spending years at sea in warm tropical waters), hulls were often payed with mixtures of tallow and additives like ground brimstone.  This treatment provided some protection against borers, but mostly reduced the turbulence along the hull, reducing drag.  The process of paying a hull in those days required a fire to heat the pitch or tallow, and could be spectacular (as well as dangerous).  Witness the engraving below of paying a hull, probably in the 17th Century.  This image appeared in G. Heck’s Iconographic Encyclopedia, first published in 1849, and used engravings by Henry Winkles, that were copied from much earlier sources.  A companion image shows caulkers using a mallets very much like modern ones.



Now, let’s go back and look more closely at the picture of the crew of caulkers working on the Alice Knowles.



In this view we see a team of 5 caulkers working on the port side of the bark, just forward of the main mast.  The vessel is empty and the masts and yards have been removed, so she is sitting in the water at wharfside, floating high.  The solid light material just visible in the bottom right of the picture is the copper sheathing, which extends above the normal, full-loaded waterline.  The caulkers are working on seams above the waterline.  The finished seams have been payed with white lead to seal them.  Some oakum can be seen in the three open seams above the sealed ones.  The man on the left is preparing a hank of oakum for use.  The next man is pounding his with his mallet and straight iron..  The third man is probably a helper, and he is carrying a bundle of oakum to the remaining two caulkers on the right.  At the feet of the second man lies a larger “hawsing” mallet, with yet another on the plank between the first and second caulkers.

One interesting feature of this picture is that the four caulking mallets that are in use all appear to be brand new mallets, with shiny steel bands, and dark (probably mesquite) heads.  All appear to be of the same manufacture—probably C. Drew & Co. of Kingston, Mass.  Despite the apparent “newness” of the mallets, it is more likely that they were just kept in top condition by their owners.  Caulkers were quite fastidious about these tools, and there are reports that some caulkers carried pieces of crocus cloth in their pockets and periodically stopped work to polish the metal rings and wood on the heads of the mallets.  This is likely the case of these caulkers.  Some cynics have suggested that this practice was less a concern about the condition of the tool, than simply a ruse to “rest” a bit from the arduous work of caulking.

 Finally, the meaning of the slots and drill holes in the heads of caulking mallets used in New England deserves some commentary.  These purposely made and modifiable slots were not, as commonly thought, to prevent splitting of the wooden mallet heads.  The teams of caulkers working on large whalers and merchant ships could comprise 20 or 30 men.  When a steel caulking iron is struck with force by a wooden mallet against a hollow hull, the sound is a loud, sharp “ping,” that becomes sharper as the caulking proceeds and the hull tightens up.  The cumulative noise from a vigorous crew of caulkers is loud, and potentially discordant and annoying.  To allay this discomfort, the caulkers modified their mallets, by creating or extending the slots in them, and by drilling holes in them.  The effect was to “tune” the mallet, putting it, as it were, in the same “key” with others on the crew and making the noise more musical.  It is interesting that caulking mallets from areas where caulking crews were smaller (on Erie Canal barges, for example) often lack this feature.

 Pictures of tool boxes and the workers that use them do have stories to tell!