TECHNIQUES UTILIZED IN MOLDING A HENRIETTA MARIE CANNON By Corey Malcom Mel Fisher Maritime Heritage Society Key West, Florida August, 1998 In June of 1998 the MFMHS received permission from the FKNMS to replace two iron cannon recovered from the wreck site of the Henrietta Marie with concrete replicas. This project had been discussed as a way of improving the experience of those visitors who make the voyage to the site. The roots for this particular idea can be found in a 1994 visit by the MFMHS archaeological team to the site of the Urca de Lima, a wreck of the 1715 fleet lost near Ft. Pierce, Florida. This site had been made an underwater archaeological preserve, encouraging the general public to share in the wreck diving experience. A number of concrete, replica cannon had been placed on the site, to great effect. As the Henrietta Marie exhibition tours the nation, divers wish to visit the wreck site as a way of paying homage to those forced to sail on her. But, as is common with colonial-era wrecks, there is not much visible wreckage. It was thought replacing the cannon would improve the experience of any visitors. A concrete and bronze memorial was placed on the wreck by the National Association of Black SCUBA Divers in 1993, and this has been the only readily visible evidence of the site since that time. A large iron box, thought to relate to the ship’s galley, lies in the reef to the north of the monument, but is difficult to locate without previous knowledge. Typical of most good ideas, though, it was not completely thought through. The specific logistics of making a concrete cannon were poorly understood, and, even worse, nothing on the subject was readily available. By scouring the internet, libraries, and brains of the few people who have been involved similar projects, enough information was found about molding and casting in general to be able to proceed confidently. The condition of the cannon should be the first issue to be considered in a molding project. If working with a cannon that has been recovered from a marine environment, it is best to make sure it has been conserved before proceeding. Because marine iron is quite susceptible to damage if exposed to the atmosphere in an unconserved state, the cannon can be significantly and irreversibly harmed during the few days it will take to complete the molding process. Cast iron recovered from a marine environment consists of a degraded, graphitized layer covering an iron core. The graphitized surface retains most of the important details, but it will separate from the core if allowed to dry before conservation. Bronze will be stable enough to work with, even if it is not conserved, but it should be treated afterwards. The type of mold to be created is dictated by the of the specific project. For the best detail, and easier removal, a rubber blanket mold can be formed first around the gun and then backed by a hard, fiberglass “mother” mold. This type will produce a very finely

detailed casting, but it will be expensive, require greater molding skills, and have a limited life span of approximately 10 years. Another mold type, and the one described in detail here, is made entirely of fiberglass. This type of mold is rigid and less likely to capture the finest of details, but is simpler to create and will last a lifetime. The following step by step guide should prove a good beginning guide to molding and replicating a cannon with fiberglass: 1) The cannon should be cleaned of dust and grime to provide an optimal molding surface.

Measuring the cannon.

Cutting the fiberglass.

2) Measurements should be taken of the gun and patterns cut to properly fit the fiberglass. Enough fiberglass should be pre-cut to lay three layers of heavy-grade mat and one layer of woven roving. 3) A series of releasing agents, to prevent the fiberglass from attaching to the surface of the cannon, must be applied. The first of these is PVA (Polyvinyl Acetate), which is the key component in Elmer’s white glue. This type of glue can be diluted with water and brushed or lightly sprayed onto the surface of the gun. Commercial PVA mold releases are also available. After the PVA coat is dry, multiple coats (ca. five) of a release wax should be applied. Paste carnuba wax, which is wiped on, allowed to dry, then buffed, works well. Finally, another coat of PVA should then be applied.

4) A PVC insert approximately the same diameter of the bore should also be prepared with the same releasing agents, and inserted 4-6 inches into the bore. 5) Coat slightly over one half of the cannon with a polyester resin. Lay a layer of fiberglass mat, and saturate it with resin. Be sure to work out all trapped air bubbles, or they will create blemishes in the mold. Two more layers of mat should be laid and then a layer of woven roving to form the exterior. Before the resin sets completely, mark the centerline for the mold and trim the excess glass with a sharp blade all the way around the gun at this line. Let the fiberglass set completely (i.e. overnight).

Laying the first layer of fiberglass.

5) Remove the half-mold by gently tapping and pulling. Soft wood wedges can be utilized, if needed. 6) Remove the PVC bore insert at the same time as the first half-mold. 7) Finish and smooth the edges of the removed mold with a grinder or sander. Do not round the edges of the mold while doing this, but rather, keep the trim line perpendicular to mold’s surface. 8) Wax the interior of the mold and cover the edges with a flange of aluminum foil. 9) Re-insert PVC into bore.

10) Return the mold to the gun, and carefully roll it over. Make sure it rests with even support. 11) Put a coat of PVA over any exposed foil. Check the gun for any blemishes in the release coating, and correct with additional PVA, if necessary. 12) Lay second half of mold the same as the first, with three layers of mat and one of rove. Overlap it, but do not let it stick to first half of the mold, but, rather, the foil flange. Let the glass set fully. 13) Remove the bore insert. 14) Tap and pull the second mold away from the gun. It may be necessary to trim some of the excess overlap to remove it. This can be done with a thin cutting blade on a flexible shaft, high-speed, rotary tool, but don’t cut into the gun! 15) After removal, trim the overlap to 1/2 inch from the edge of the first half-mold. The two halves should readily “snap” together, and come apart with a gentle pull. The cannon mold created from this process is designed to be poured from the muzzle. This requires it to be stood upright, on the breech end. The mold itself is not designed to do this - a framework and base that can hold the mold in place and bear the weight of the poured concrete needs to be constructed. The specifics of this mold support system will vary as dictated by the individual dimensions of each gun.

The two halves of the completed mold.

The two halves together.

Detail of the overlap.

Painting a concrete cannon.