A light wooden goblet with a narrow stem and flared bowl features dark grain patterns and a black vertical stripe; it sits upright on a wooden table, with bookshelves behind.

Wooden Goblet Rx

Spring 2014

By Tom Pawlak — Retired GBI Technical Advisor

Vern, a good friend of mine, turned the exterior of a wooden goblet made from a nice piece of spalted sycamore. Unfortunately, the blank was not as dry as he thought and it cracked along one edge as it sat uncovered on his lathe overnight. He called to see if there was anything available for gluing it back together. I said I had some ideas and asked him to drop it off at work so I could take a stab at the repair.

I asked if he wanted me to match the wood color or to accentuate the crack by filling it with a dark epoxy. He decided a bold black crack fill might make for an interesting feature in the goblet so I went about setting up for the repair.

The first thing I did was dry the goblet a bit more so the wood would not continue to shrink after the crack was repaired. I put it in the warm/dry environmental hut we affectionately refer to as the Arizona Room. This room is set at 100°F with very low humidity. I meant to leave it in there for 3-4 hours in front of the forced air electric heat source. I came back three days later. (Yes, I had forgotten it over a weekend and the crack had increased in width from 1/8” wide to 1/4” wide- a 100% increase!) Embarrassed by the mistake and for the significantly wider crack, I called Vern to give him the bad news. He said, “That’s OK. It was junk before I called you. Just go ahead and fill the crack.”

My plan was to use G/flex 650, the liquid version of G/flex, so it would flow down into the crack. I chose G/flex Epoxy over 105 Resin-based epoxy because it is more flexible and not as hard. It machines similar to wood when you cut it compared to 105 Resin/hardener based epoxy that is noticeably harder when cutting/machining. G/flex 650 Epoxy is similar in viscosity to room temperature honey and like honey is thinner when it is warm. I began by warming the goblet to 100°F. I covered the crack with clear Cellophane tape to keep G/flex from leaking and so I could see the epoxy as it filled the crack.

Carved wooden vase-shaped sculpture split down the center, revealing a narrow interior seam; it sits on a small base and is wrapped in clear plastic on a white, crinkly surface.

I added a bit of 423 Graphite Powder to the epoxy (see Bruce Niederer’s article Adding Pigments to Epoxy in EPOXYWORKS #21 for more ways to color epoxy). I mixed it thoroughly and used an 807 Plastic Syringe to inject it into the crack. To get the epoxy injected near the bottom of the crack, I slipped a 1/8” diameter plastic straw onto the tapered tip of the syringe (see photo) so the epoxy did not have far to flow.

Syringe-like adhesive applicator; injecting resin into a crack in a wooden piece; in a workshop with green-gloved hands.

Injecting the black epoxy into the 100°F wood lowers viscosity on contact which helps it flow into recesses of the crack and lets air bubbles rise to the surface and escape.

A red pencil is pressed into a deep crack in a light wooden plank, as the split widens along the grain; blurred workshop tools and surfaces linger in the background.

A hollow wooden vessel with a crack is being filled with dark epoxy from a syringe by a gloved hand; on a workbench, bottles labeled West System epoxy sit nearby. Transcribed text: WEST SYSTEM G-FLEX EPOXY PART A RESIN WEST SYSTEM G-FLEX EPOXY PART B HARDENER

I called Vern the following day to let him know his goblet was ready to go. Vern reported later that when he turned the inside of the goblet on the lathe the cured G/flex turned just like wood with the shavings at times coming off the cutter in a continuous ribbon.

Vern eventually applied his favorite wood sealer and wood finish to give the goblet a nice subtle shine. I think from the attached photos you’ll agree that it was worth saving.