Historical Furniture Finishes. Part 1

Yannick Chastang investigates 18th-century finishing techniques.

Introduction

The following two-part series examines the details of furniture finishes that were typically applied around the 18th century. Drawing on some of the most embellished and technical examples of furniture, our author details the choices available at the time, and how various products evolved to meet new demands and tastes in furniture finishes. He also expounds on the more practical use of such products, including appropriate applications, ingredients used in various finishes, optimal drying conditions, and useful techniques on how to apply such finishes.

Roubo’s Revival

While Roubo’s is the most complete treatise published during the 18th century, many of Roubo’s entries originate from other contemporary and older publications. Roubo was the son of a carpenter, and did not have first-hand experience of all the techniques and materials he described. The publication of the English translation of A.J. Roubo’s technical treatise on cabinetmaking (To Make as Perfectly as Possible published by Lost Art Press in 2013) has sparked considerable interest in 18th-century furniture techniques. His encyclopaedic volume has led to the rediscovery of many long forgotten techniques and recipes. Woodworkers around the world are currently carrying out practical experiments to test Roubo’s practices. As part of this global inquiry, furniture finishes have attracted a lot of interest. However, our understanding of historical finishes is still clouded by myths and misunderstandings.

Yannick Chastang has had a head start on many of his English speaking counterparts having had access to Roubo in its original French for the past 20 years. He has been researching and experimenting with original recipes, from Roubo and from other 17th- and 18th-century woodworkers with a particular interest in wax finishes. Wax finish has, for a long time, been a favoured option for both makers and conservators, and its application using the little known ‘polissoir’ provides an insight into 18th-century finishing techniques.

Myths and realities

Our understanding of historical finishes is still very patchy, and is based on a variety of incomplete historical sources. Material identification, using some of the latest scientific analyses, is slowly helping to fill the gaps in our knowledge. But very few pieces of furniture, if any, have retained their original finish meaning an absence of viable samples for analysis.

The effects of time and regular restoration have destroyed most original finishes. If, by chance, an original finish has survived it’s unlikely to be intact; regular dusting, cleaning and natural ageing and drying out of the materials (often referred to as cross linking) would, at best, have resulted in the loss of original transparency, colour and gloss; at worst, the finish will have perished entirely. Even on the highly prized musical instruments made by Stradivarius, many of the finish surfaces have either degraded or been replaced. Great mystique still surrounds the sound quality of Stradivarius’s instruments, which is supposedly linked to his unique choice of finish; essentially an oil-based resin varnish.

Unlike musical instruments, furniture’s original finish was far less valued, and was deemed to have the practical purpose of enhancing the wood and protecting the surface. Furniture finishes were regularly renewed, either because they had degraded, or as part of a repair of the piece as a whole.

The famous Bureau du Roi

In 1776, Riesener, with the help of two craftsmen, was at Versailles restoring the famous Bureau du Roi and a commode. Based on his bill, it is possible to establish that in less than two weeks, Riesener and his helpers dismantled, scraped and sanded the marquetry, cleaned the bronzes and repolished the Bureau du Roi, and worked on the commode (avoir été avec deux ourviers….avoir raclé et repoly tout la marqueterie et netoyé la garniture de bronze).

This was obviously an amazingly productive two weeks – the Bureau du Roi being one of the most complex pieces of furniture ever made. Its dismantling alone would have taken days. As regards the finish, we know that the resin-based polish available at the time of Riesener (and Roubo) would not dry quickly enough to be applied in this short a time frame. Riesener’s bills for mahogany furniture delivered to the crown in 1786 also clearly mention ‘poli a la cire en dedans et en dehors’ (wax polish inside and out).  

Coloured Varnish

The ‘best white varnish’ was a rich, translucent finish commonly used during the 18th century. It was made using sandarac resin. Shellac (on the right) was only available in dark red during the 18th century. The shellac pearls on the right are the pure, natural colour of Indian origin seedlac, an unrefined, unbleached natural form of shellac. Compared to the lightly coloured sandarac, it is easy to appreciate why natural shellac was not suitable for light coloured wood and marquetry but was favoured for rosewood or mahogany furniture only. The study of historical recipes needs to encompass the available materials and their inherent limitations at the time.

Pumice, sandarac and shellac

Today, it is possible to apply a respectable French polish using shellac in only a few days. French polish, at the time of Roubo, was much different, and its application was greatly influenced by the materials to hand. It is in fact believed that French polish, as we know it today, is a 19th-century improvement on previously used polishing techniques. Most of the techniques described by Roubo, such as the use of pumice powder, and most of the materials described in Roubo, appear to be those used in today’s French polish.

However, Roubo and his contemporaries do not favour shellac, but, instead, praise the natural resin sandarac, with its application by brushing. The reason for using sandarac instead of shellac is easily explained by the colour of shellac available at the time. Modern day alcohol used as a solvent in French polish differs greatly from its 18th-century equivalent – the so-called ‘esprit de vin’. Distillation processes have improved to a point that modern alcohol has a water content of less than 5%. 18th-century alcohol is estimated to have contained, at best, 65 to 70% alcohol and the rest water.

Different finishes for different woods

The high-water content of the esprit de vin would reduce evaporation rate and would have resulted in a cloudy finish. Additionally, the shellac available at the time of Roubo differs in colour and wax content. Archival evidence reveals that shellac was only available in a dark version, similar to our modern sticklac, seedlac or the more refined dark garnet shellac. Lightly coloured shellac (commercially known today as de-waxed or blonde shellac) is obtained via a difficult process of removing some of the natural wax content from the pure sticklac and by chemically bleaching the shellac. As a result, Roubo only recommended shellac for dark woods such as rosewood (Dalbergia retusa). Applying a dark shellac finish to a colourful marquetry (on both European and English furniture) or to a light-coloured wood would have spoiled it.

Instead of shellac, Roubo recommended using the best ‘white polish’ for light coloured marquetry. According to Roubo, the best white polish was not only suitable because of its almost translucent colour, but he also states optimistically that the best white polish would stop the colours of the marquetry from ‘evaporating’ and stay colourful longer (‘saisir leur couleur, qui, ne pouvant plus s’evaporer, reste toujours dans le meme etat’). This is an amusing misunderstanding of the true reason for the discolouration of wood. It also demonstrates that UV protective varnish was ‘invented’ during the 18th century (albeit not very successfully!). Sandarac-based finishes were not invented by Roubo, and the best white varnish, as described by Roubo, finds its origin, almost word for word, in the treatise on ‘Japaning (sic) and Varnishing’, written in 1688 by Stalker and Parker.  

On paper, a sandarac-based finish provides the perfect solution.Sandarac finish produces a clear and translucent finish; it beautifully enhances the colour of the wood, and does not obscure marquetry. However, without exception, all experiments have demonstrated that sandarac finish is extremely slow to dry and is very difficult to work with. The author’s attempts to create a thick and glossy finish, similar to today’s French polish, were only successful if layers between applications were left to dry for several weeks. One must therefore conclude that if sandarac was used, it was limited to a couple of applications.

Conclusion

In view of such evidence, it appears that a wax finish must have been the most practical option, and therefore the most ‘authentic’ finish used during the 18th century for the large majority of furniture produced. Darker furniture may have received an application of dark shellac, while the more expensive colourful furniture could have been finished with a couple of layers of sandarac. But furniture almost certainly never had the thick glossy appearance commonly associated with French polish. In part two we will take a close look at the Polissoir.

These were commonly used in the 18^th century to apply polish to furniture and musical instruments. By constructing from carefully selected natural materials, and when used with the right technique, these handheld tools could achieve high standards of finish.

Intrigued?

We will also look at how to make one of your own.

Further reading