When confronted with the choice between repairing a heavily damaged (ie chewed through) ebonite stem or making a replacement stem, I will always lean towards making a replacement. This is because I have yet to find a satisfactory method of patching the stem that I am confident will provide a long-lasting repair. The bite zone is the weakest part of a pipe and it takes the most abuse. Ebonite has a soft mouth feel, yet is a tough material that can take some punishment. Most, if not all, patch materials are going to be less resilient to to the toothy tortures inflicted by the clencher. So if the pipe owner chomped through an ebonite stem, they will chomp through the repair even faster.
There are occasions when a patch makes sense. For example, a particularly ornate stem, or a stem containing a logo or some stamping that would be very difficult or even impossible to replicate in a replacement. In my early (pre-internet) days of restoration work I tried a number of epoxies to attempt patches on these sorts of stems. These were estate pipes for my own use, so I was willing to experiment. The epoxies were all complete failures. Most cured epoxies are surprisingly soft and pliable and even with careful surface preparation they would tend to delaminate from the stem after just a few smokes. While many pipe repairmen have had great success with the the current favored approaches of using cyanoacrylate (super) glues, in my hands these repairs have been less than ideal. The polymerized cyanoacrylate is generally tougher than epoxy, but it has a low shear strength and easily fractures. It does a good job of filling small scratches and dents, but falls short when patching actuall holes in the stem. The inclusion of activated charcoal seems to actually exacerbate this problem in my expereince. None of these solutions provided a repair that I found would hold up to normal clenching pressure for more than a short time.
Recently I came across a potential patch material that I believe holds some promise. West Marine is a company that specializes in products for the boating industry. Their line of epoxies are designed to work under a variety of harsh conditions and have been optimized in terms of flexibility and durability. They also take color well and once fully cured can be filed and sanded to shape and to a reasonable finish.
I had been wanting to try this epoxy for a while, and the opportunity presented itself when I was asked to restore a GBD bent brandy with some significant stem damage. It would have been a shame to lose the original stem because it’s unusual geometric shape really seems to complete the overall look of the pipe, and it contains a near-pristine GBD logo. The owner was graciously willing to serve as a test subject and I took this as an opportunity to try a new approach.
The pipe was not in terrible shape other than needing a good cleaning. But as can be seen in the pictures below the stem was severely damaged in the bite zone with a large piece missing from the bottom.
The first step was to fully clean and sand the stem and buff it to an essentially final state. This allows me to see the full extent of the damage and detect any remaining dents or tooth chatter that might need to be further sanded or filled.
The area around the repair needs to be very clean and roughed up enough to allow the epoxy to bond. I used a round machinist burr to roughen the surface and then cleaned it with a brass brush and some ethanol. I prepared the stem for the epoxy patch by cutting some pieces of old business cards (red and white striped thing in the photo below) to a shape that filled the internal area below the patch to protect the airway. Several layers were used, and the top layer was covered in clear packing tape to prevent the epoxy from bonding to the card. I then used masking tape to form a dam around the stem to receive the epoxy.
I mixed the epoxy thoroughly with some black pigment and poured it into the dam. The epoxy was allowed to cure for 24 hours before removing the tape and card shims. I then repeated the process on the top of the stem to fill in a few deep tooth marks and add some material to the thin ebonite.
The final results were not pretty, but the repair seemed tough and well adhered to the stem. As you can see in the photos, the card stock shims worked well to help keep the airway open and form the start of a new funnel.
The cured epoxy worked well and the a new bite zone was formed using files and sandpaper. The funnel was also re-established using files and the airway was polished. I found the material somewhere between ebonite and acrylic in terms of how it worked.
After final sanding and buffing the repair is visible, but not more so than what would be achieved with superglue. It is aesthetically acceptable and will allow this beautiful GBD to go back into service with it’s original stem. I’ve asked the owner to let me know if he experiences and problems with the patch, so for now we will have to file this method under promising.