Often objects have undergone multiple campaigns of conservation/restoration before we treat them. That was the case with this opaque white candlestick which came into the lab with its foot broken into several pieces. We can tell that the candlestick had been repaired at least twice already.
The earliest repairs on the candlestick were done using a technique called riveting. With this technique small holes are drilled into either side of the break and small metal clamps (or rivets) are inserted into the holes to hold the pieces together. Two riveting methods were commonly used: the through-and-through rivet or lacing method and the staple method. With the through-and-through rivets, holes are drilled all the way through the glass or ceramic and a thin metal wire is laced through the holes repeatedly. In the staple technique the holes are only drilled part way through the glass or ceramic and at a slight angle towards the break. A thicker metal wire shaped like a staple is then inserted into the holes. The slight angle of the holes and the shape of the rivet pull the two pieces together, making a water tight join. Staple rivets often allow the repairs to only be visible from one side. Riveting was used from ancient times to well into the 20th century. One of the main reasons this technique was used was the lack of an adhesive that bonded well to smooth surfaces like glass and porcelain. Such glue was not available until the 20th century when synthetic glues were developed.
Because the rivets were no longer in place by the time the candlestick came to us for treatment, we know that there was a second campaign of treatment in which the rivets were removed. Therefore the current treatment is the third or perhaps even fourth or fifth time this object has been treated.
The candlestick came into the lab because the adhesive from the previous repair was starting to fail. The first step was to remove all the old glue. This was done by placing the candlestick in a vapor chamber created with two layers of polyethylene bags with a small amount of methylene chloride. Methylene chloride is one of the most hazardous chemicals we use and is always used in the fume hood. After about an hour the old repairs came apart and the fragments were removed from the vapor chamber. Remnants of the old adhesive were cleaned off the glass with a scalpel and acetone on a soft brush, using a microscope when needed. The fragments were then washed with non-ionic soap and tap water followed by a rinse with de-ionized water.
Next the fragments were re-assembled piece by piece with a very stable acrylic adhesive. Sometimes this is done using adhesive tape to hold the fragments in place while the glue sets, but I prefer to use gravity. After applying the glue I squeeze the two fragments together for a minute or so and then position them so that one fragment is balanced on top of the other. The advantage of this technique is that you don’t need tape which can be harmful if you’re working with glass with a fragile surface. Unfortunately it doesn’t work well with all adhesives, you need one that sets relatively quickly.
When re-assembling an object you have to think about what order to join them so that none of the fragments get locked out. In this case the six fragments of the foot were joined first and then the stem was joined to the foot. Since the stem is relatively heavy I used a clamp stand to hold it in place while the adhesive set.
The next step was to deal with the rivet holes. Old repairs become part of an object’s history and can hold an historical interest. Because of this old repairs such as rivets are often left in place and sometimes even conserved themselves as long as they are stable and don’t pose a risk for the object. In the case of this candlestick the rivets have already been removed leaving behind holes that are visually disruptive. In order to preserve the history of the rivets and the integrity of the piece only the four holes on the upper part of the foot were filled.
The rivet holes as well as the losses around the break edges were filled with an epoxy. The epoxy was thickened into a paste with fumed silica and tinted to match the white glass with dry pigments. The rivet holes were filled with a glob of acrylic glue before being filled with epoxy to make the treatment more easily reversible. Excess epoxy was removed with a scalpel and acetone on cottons swabs. After the epoxy had fully set, the fills were polished to match the shine of the glass.
Finally the enamel decoration was in-painted on the fills where needed with acrylic paints.
The whole treatment took 5 hours over a period of 4 months.