Experiments with Amber: Recreating an Early Modern Varnish Recipe on the History of Design Course


Research
June 14, 2017

As part of the V&A/RCA History of Design MA course, during the spring term students have the chance to explore early modern making techniques as a form of historical research through practice.  With the support of V&A curators, conservators and tutors, students recreate early modern recipes to reflect on practices of making and the nature of artisan knowledge and skill.

The Thinking and Experiencing ‘Techne’ course is a satellite project of the ‘Making and Knowing’ project based at Columbia University, in New York, and this year was also a collaboration with the V&A’s Robert H. Smith Scholar in Residence, Dr. Spike Bucklow, from the Hamilton Kerr Institute. For more details on the workshops see News & Events at the RCA.

In this post, students Liddie Caston, Jessica Eddie, Ayelet Shats and Cara Robinson reflect on the experience of making a wooden furniture varnish from linseed oil with the added benefits of amber. The inclusion of amber allows the varnished finish to set and dry more quickly than a simple linseed oil finish. As less time was needed between applying different coats of varnish, this quickened the overall production of wooden furniture. Multiple layers of varnish also increased the protective finish and therefore quality of a piece of furniture:

The varnish recipe we followed from a sixteenth-century French manuscript now in the Bibliothèque Nationale in Paris is rudimentary with few precise details, such as temperatures, which you would expect in modern instructions. It states:

‘The Germans boil the minium intensely in linseed oil, and to give it the consistency of varnish, they mix in heavily pulverized amber’.

We approached the process in three distinct stages: preparing the amber, heating the linseed oil and melting the amber, and finally combining the linseed oil and amber.

Preparation of the Amber

Pulverised amber
The unprocessed amber in its raw state before using a pestle and mortar to ‘pulverise’ into a fine powder

The amber had to be finely ground so that it was easier to melt and combine with the linseed oil. Although not a feature of the original recipe, we prioritised health and safety and wore goggles and protective masks to avoid breathing in the fine dust. Grinding the amber produces a very sweet treacly aroma, a reminder of amber’s origins as a sticky tree sap before crystallisation. When you see amber in its raw state it is obvious why it was chosen as a finish to enhance and protect wood, as it is hard yet translucent and golden in colour.

Heating the Linseed Oil

Heating the linseed oil to 200 °C
Heating the linseed oil to 200 °C

We had to heat the linseed oil as well as the amber, so the two could be combined without cooling. As we were using a small camping burner, the linseed oil was stirred gently at regular intervals to encourage even heating and later a loose tin foil jacket was placed on top to maintain a steady temperature. As the oil heated up past 100 °C, it became slightly thicker and gave off a rich diesel or citrus aroma that became unbearable to be next to for long periods of time at 200 °C. After 72 minutes the oil reached 200 °C and at this point we added lead minium, as instructed in the recipe. Minium is a bright, orange-coloured powder added to help bond with the amber. This turned the mixture to a vivid shade of orange.

 Senior V&A furniture conservator Dr Nigel Harman adding the lead minium to the linseed oil

Senior V&A furniture conservator Dr Nigel Bamforth adding the lead minium to the linseed oil

Melting the Amber

Having spent the previous week grinding the amber down to a fine powder, we were particularly keen to melt the amber correctly, especially as we knew that students last year had encountered challenges at the grinding and melting stages. As the melting point of amber is high, we used the modern day equivalent of a white hot flame: a scientific heating mantle with a round bottom flask to melt the powdered amber. Using a transparent glass flask also allowed us to see what was happening to the mixture.

The heating mantle gently heating the powdered amber
The heating mantle gently heating the powdered amber

During the melting process, the amber became a very dark colour and highly sticky, which made us concerned that the mixture had been ruined and would be unsuitable to use. We relied very much on our senses of smell, sight and touch (via the thermometer) to assess the melted amber. At times the mixture was grainy and so stirring at regular periods helped break the grains down whilst we remained careful not to let the mixture cool. As with the linseed oil, we put a foil cover over the top of the flask to ensure even heating. As the mixture fully became liquid and reached 300 °C it began to smell so strongly that anyone close to it had to wear a mask. Overall the amber took 64 minutes to reduce to a liquid suitable to combine with the linseed oil.

Scraping the melted amber onto paper to check the consistency as the black appearance looked like it had burnt
Scraping the melted amber onto paper to check the consistency as the black appearance looked like it had burnt

Combining the Linseed Oil and Amber

The gentle stirring of the linseed oil as the melted amber was added

Gently stirring the linseed oil as the melted amber was added

This created a significant amount of smoke, which soon died down
This created a significant amount of smoke, which soon died down
The finished amber
The finished amber varnish (seen in the beaker). The neck of the wooden spoon shows the different stages of the process from linseed oil to addition of the minium to the addition of amber

When held to the light the mixture seemed to have dark impurities, which could have been in the ground amber or where some of the amber had burnt in the round bottomed flask. However, the mixture could be filtered to remove these (we were advised that white bread would also filter this well if we wanted to remain in keeping with the period of the recipe). The final mixture looked very dark in colour and so we were curious to see how it would appear on wood – a point for discussion in our next blog post.

The concept of techne relies heavily on the use of previous or tacit knowledge of a process or materials and we found this to be very relevant with this experiment. As the recipe text did not include much detail,  we often depended on our senses and intuition (as well as expert advice) to ensure the process was working. We would like to thank Dana Melchar (Senior Furniture Conservator, V&A), Dr Nigel Bamforth (Senior Furniture Conservator, V&A), Nick Humphrey (Curator of Furniture 1400-1700, V&A), Dr Spike Bucklow (Robert H. Smith scholar in Residence, from the Hamilton Kerr Institute)  and Dr Simona Valeriani (Acting Head of History of Design, V&A) for their enthusiasm and expertise during this lab class.

To see what else V&A/RCA History of Design students have been up to, check our pages on the V&A and  RCA websites and take a look at Un-Making Things, a student-run online platform for all things design history and material culture.

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