30 marzo 2005
A rational look at classical coatings
After graduating from the Newark School of Violin Making I worked as a violin restorer and maker for about ten years. On returning to The Netherlands in 1987 I became involved in industrial varnish and printing Ink technology which has greatly helped my understanding of varnishes in general.
Since 1996 I combine the two by producing specialised varnish materials for violinmakers.
Like most of us, compared to what I have learned about varnish over the past twenty years, I have learned a terrifying amount about what does not work. I am however sure that the qualities that we admire in classical varnishes cannot be attributed solely to a substance that was once held in a container. Where it concerns the wood work, it are not just the materials and the artistry of the Luthier that decide what the instrument is going to look like. The construction methods and even the tools used exert an important influence on the final result. A clear example of this influence of method and tools on the esthetical quality of the resulting work is the Cremonese method of drilling the ff hole circles and mapping out the rest of the ff hole to the pre-drilled circles.
Similarly in varnishing the system behind the build up the different layers and the methods used to apply these layers influence the appearance of the finished coating.
Perhaps the biggest common factor amongst the varied coatings that we today classify as classical varnishes, will turn out to be not their ingredients, but the “construction” method behind the build up of the various layers and the way in which these were applied.
Over the years I have become convinced that the Byzantine finishing system for painted objects was the theoretical basis for classical makers when it came to varnishing.
Because this system had been imbedded in the cultural heritage of artists and craftsmen for centuries, it was a logical and possibly even unquestioned method to follow for any wood worker. In principle the same method was used to decorate all kinds of objects and to execute tempera and oil-paintings.
For a classical violin coating though, at least one important criterium differed.
Unlike in a painting, the total coating had to be transparent because the carrier – the wood – played a crucial role in the appearance of the finished work.
It is the intention of this article to explain the ratio behind this hypothesis and to bring to discussion a few plausible practical implications.
Traditionally the coatings seen on Italian violins made between 1550 and 1750 are referred to as “classical varnish“. We make a few subdivisions (based on very obvious differences in appearance) into towns of origin. This has resulted in descriptions such as ”wonderful Venetian varnish“, “majestic Cremonese varnish” or at the low end of the price range, ”rather dry but pleasing Neapolitan varnish“.
Even though some classical makers have reached an almost mythical status today, in their time they were fairly standard craftsmen.
The violin may be aesthetically superior, it does not however require a higher level of craftsmanship than that shown in lutes, viols, or harpsichords of the time. If anything, the reverse is true.
Arguably though, the violin remains one of the most difficult artefacts to varnish evenly.
It has always intrigued me that some of the earliest violins known to us are already coated in perfect classical varnishes. So unless I want to believe that Andrea Amati invented a whole new type of varnish, which for 200 years was secretly passed on to seemingly unconnected violin makers in different regions and then collectively abandoned around 1750. I will have to acknowledge that classical varnishes and/or their ingredients were already well known by 1550. And that these products were more or less readily available in the different localities were they were used. In contrast to artists, who usually quickly embrace new technologies in order to express their ideas, craftsmen tend to go with what is tried and proven. It is therefore most likely that we can push this date back by at least fifty years. This would place the origins of “classical varnish” back at least into the Renaissance.
In April 2004 I was allowed to examine three instruments from the collection of the Ashmolean Museum Oxford. In reverse chronological order these were the Ashmolean catalogue numbers:
7 (D.8:7) A Bass Viol with Cello features Antonius & Hieronymus Amati Cremona 1611
11 (D.8:1) A Viola (Charles IX) Andrea Amati Cremona 1574
8 (D.4:1) A Lira da Braccio Giovanni Maria (dalla Corna) Bresiano Venice c.1525
In day light, the very well preserved varnishes on these three instruments look very similar.
Under U.V. light they are identical. The Lira da Braccio was made some 25 years before the earliest known dated violin by Andrea Amati and the generally accepted start of the classical period.
Although the Renaissance had a large impact on academic, artistic and philosophical aspects of society, it did not have much influence on the man in the street. Craftsmen still worked according to the hierarchy and codes that the Byzantines had brought to Europe during the early middle ages. Also, the raw materials and the way in which these were produced did not change much. Certainly, because of expanding trade routes the provenance of materials sometimes changed and new materials including ingredients for varnishes were introduced constantly. But these mainly added to the choice, and most did not simply disappear around 1750. In any case; regardless of whether we think classical makers made their own varnishes or bought them ready made, they would have been dependent on the raw materials used in other crafts. If only because the average violin maker would not have used much more than half a kilo of varnish a year. Even in their time this did not create a raw ingredient buying force of any substance. A more plausible explanation for the disappearance of classical varnishes seems to me to be the following.
Between 1600 and 1700 the fashion in woodwork finishes changed to hard and glossy in an attempt to emulate Japan lacquers (in the Middle Ages these had been a highly prized rarity in Europe and were imported from China overland) This caused a frantic search for recipes to copy these technically superior lacquers which resulted in an enormous interest in spirit varnishes. Also; oil varnishes from now on had to be hard and glossy. This change in concept caused a change in formulation and quality criteria for the raw ingredients of oil varnishes. In addition the advances made by the newly founded science of (Iatro) Chemistry started to influence the until then predominantly Alchemical production techniques of many materials and chemicals that might have been used.
Because of wars, famines and diseases Europe’s population had been fairly stable for the best part of a millenium, with the majority of people living a semi enslaved existence.
After the second pestilence the fast growth of the now slightly less enslaved population caused an increase in the demand for all kinds of goods and more people now had to be paid for their labour.
As a result the production of all kinds of goods had to be increased and rationalised.
Time was slowly becoming money.
Contrary to what many still believe, classical varnish did not disappear overnight. Throughout the entire period of its use, its various components were subject to gradual change. Not only is there a large difference in the coloured coats, even the much praised “grounds” differ considerably. And it is only when the quality of these “grounds” finally changes beyond recognition – somewhere between 1750 and 1800 – that we no longer recognise and categorise the many different Italian varnishes as “classical“.
In my opinion it has added greatly to the confusion surrounding classical varnish that most of these changes took place within a (in retrospect) relatively short period. Thus giving us the impression that only one crucial and now lost element had been responsible for all that is admirable in classical varnishes.
Observations based on UV light comparison
What we see when we look at a transparently varnished object is of course not just the varnish, but the interaction between the carrier material (in our case wood) and anything that is in between this and the physical surface of the top varnish layer.
All the various layers in between these two extremes are together called the “coating“
It is already common knowledge that when viewed under Ultra-Violet light of about 390 nanometre wavelength (also called a blue or black light), classical coatings as a rule reveal an opaque yellowish-white fluorescent layer underneath the coloured varnish.
This layer has become known as the “classical ground“
Most varnish materials have a unique fluorescent colour under UV light, but this does not mean that a fluorescent colour is unique to one material or composition, it therefore offers no means of positive identification. In fact various waxes, drying-oils and resins all show a yellowish-white fluorescence, as do countless combinations of various other materials.
So consistent is the presence of this ground, that if it is not detected on an otherwise fine looking instrument, most of us agree there is reason to suspect the instrument may not be classical. Probably because of this ever presence, the ground has however in my opinion been credited for too many of the qualities that make classical coatings so desirable.
The ground can be very thin and not detectible in daylight, or it can be obviously present to the naked eye as a thick clear layer underneath the coloured varnish. As for example on many Guarneri del Gesù, Montagnana and Storioni instruments. It is my impression that in general grounds are thicker on less refined instruments, especially those of the later classical period.
Giving us a clue to at least one of the reasons for it’s use, the smoothening of roughness in the woodwork below. In addition, under UV light on many light coloured instruments (notably those of the Milanese school), the top-layer, “the varnish” simply seems to be a continuation of the ground. In accordance with this; the surface of these varnishes is usually comparatively hard and wear resistant, they look and feel leaner or less fatty, and there is much less evidence of thermo-plasticity amongst these varnishes. Or in other words, they do not get pushed around by heat or pressure as easily as most of the stronger coloured varnishes seem to.
Scientific research by Claire Barlowº has revealed that random samples of classical ground layers contain particle matter which could be classed as filler material.
Only in a drying oil medium will some filler materials remain transparent upon drying of the medium.
All of this suggests that the ground coat has the characteristics of an oil-varnish, and could be seen as a transparent equivalent of the gesso from the ancient painting schools.
Under UV light it can be verified that where the coloured layer of the varnish seems to have chipped away from the ground it is in fact the yellow-white fluorescent ground which has chipped away from the wood. In doing so it has taken the coloured layer “the varnish” with it. The C bout area on the back of a well preserved golden period Stradivarius violin will usually provide ample opportunity to witness this.
This suggests that the ground-layer has more affinity with the varnish than with the wood or whatever is underneath, and also that the varnish is more flexible than the ground. The resulting bare? spot always looks just as good in daylight as do areas that still have ample ground left on them.
Even heavily worn areas of instruments where all varnish and ground layers have long since disappeared, usually still display two of the main three characteristics that we regard as typical for classical varnishes namely :
1 The optical qualities that we traditionally have ascribed to the no longer present ground.
2 A stunning resistance to dirt, sometimes (as on the edges of scrolls) more than 1mm
into the wood when worn away.
The 3rd characteristic – being the presence of the yellowish white fluorescent ground coat underneath intact varnish surfaces – is obviously no longer applicable.
If two of these characteristics remain even when the “classical varnish” and the “classical ground” have gone, there must be at least one more “classical” component contributing to the “classical illusion” besides varnish and ground. And this component is more likely to be responsible for the above mentioned caracteristics 1 & 2 than either varnish or ground.
The opposite scenario goes a long way towards proving the point.
I have examined a Cello by Ludovico Rastelli of Genoa, almost completely covered in original varnish. In daylight this had a nice enough, but by no means classical looking ground.
It did however looked perfectly classical under UV. The date of the instrument was 1840!
In my opinion at this late date Ludovico could still buy or make a near enough classical ground layer. But whatever he applied to his cello underneath the ground no longer gave the same results as 100 or even 60 earlier. This causes the total of his coating to appear not quite classical enough.
Historical practice _ A plausible explanation
A coating system consisting of at least three steps, of which the middle one arguably serves as a gesso, brings to mind the Byzantine tradition that is still the basis of many coating systems used today
As is implied in the early 15th century manuscript “Il Libro dell‘ Arte” by Cennino d‘Andrea Cennini¹ any painted work, be it on stone, wood, or metal (the same system was used on canvas later on) should in principle be finished in five steps, the purposes of which are:
1. Priming -To prepare the substrate so that it will accept the coating and possibly
improve its quality. This does not necessarily mean that a substance has to
be applied to the substrate. Sometimes simple smoothening or degreasing
operations were considered enough. For wood; treatments and preparations
that safeguard it from dry-cracking or insect attacks fall into this category.
2. Sealing -To take the “hunger” out of the substrate, so that the ground will not
excessively sink into it. In the case of classical coatings it could also have
been used to increase the translucency of the wood and give the fibre some
extra protection. A sealer should never! take on the role of a ground.
3. Grounding -To provide a stable and even foundation for the actual painting.
“Even” should be interpreted not only as in smooth, but also even in it’s
acceptance of paint or varnish. In classical coatings it is the ground that fills
the pores of the wood, not the sealer!
4. Painting -To apply colour or an image. If a varnish holds particle matter it is technically
speaking a paint. Our habit of talking about classical coatings as varnishes,
causes us to think about and classify them as such. This may limit our
willingness to consider anything that is not runny or easily brushable.
5. Varnishing -To protect the painting from outside influences (moisture, dirt) and to even
out differences in the surface texture. These will appear in paintings because
of the many different pigments used. In historical painting methods, different
pigments sometimes required different media. Also early paintings were often
made by using a variety of techniques and materials in one painting.
The key and central role in the Byzantine system is performed by the third step, the ground.
In painting this is usually referred to as the “gesso”. In a very real sense it must have been understood to be the foundation that gives stability to the entire coating.
The art of painting; wether figurative or abstract, has had close links with spirituality from it’s earliest beginnings. When the Christian figurative arts developed in Byzantium and Europe, painting was still almost exclusively practiced by members of the clergy. It was a generally accepted dogma of the time that humankind was only capable of copying nature, God’s original creation. Alchemical illustrations often portray mankind and the arts as a chained monkey for similar reasons. We, through our labours (the artificial) were supposed to aspire to and celebrate the original (the natural) Since God’s original creation was thought to be build on stone, the use of a mineral ground in painting may well have had religious origins. By the time the classical makers came along, this was off coarse already ancient history.
Since the publication of Mrs Claire Barlow’s° research results, many methods and materials have been suggested to explain and duplicate the presence of particle matter in the ground layer. Only a few of these ideas take historical practice into account. None have given any thought to the original function of grounds. Once we have accepted that the classical ground – because it is transparent – must be basically an oil varnish with filler material, many materials could be considered as candidates for this filler material. We should realise though, that transparency is only a specific requirement for classical coatings. And that the essence (and original purpose) of a ground is to provide evenness and most of all stability. We should not use a filler material nor anything else simply because classical makers did, but because of the reasons why they used these materials.
The Byzantine system was not a pan European ISO norm that had to be followed at the risk of loosing your license. It should be seen more like a code of good conduct.
It was the judgement of the master overseeing the work, and the work itself, that dictated which materials or compositions were going to be used for each of these steps. Materials and compositions did not have fixed purposes, but were seen to be endowed with certain qualities that could come in handy for a different purpose in a different situation. As an extreme example: hide-glue was in some panel-painting traditions used as a primer (thin and hot), as a sealer (thick), in the ground usually mixed with plaster (the “gesso“), and even to temper some of the colours.
The practical implications of the use of this system when building up a transparent coating like a violin-varnish is explained below.
If the ground holds filler material, and is transparent, it must be drying oil based.
It could then in some traditions also have been used as a sealer (step 2).
This would cause (amongst other things) better adherence to the wood, resulting in less chipping away of the ground and varnish.
The ground could also double up as the varnish (step 5) This would make the varnish light in colour and extremely tough and wear resistant which would result in a more gradual appearance of the wear.
If the medium for this ground was of sufficient quality it may even have been used without filler.
Making the ground indistinguishable from the varnish proper.
In cases where the varnish provided colour, obviously step 4 could have been omitted.
So even if the same compositions for each step would have been available to different makers, a lot of variation in outward appearance could already have been achieved by variations within this system.
Moreover there may not always (appear to) be five steps in the coating.
Even though “varnish” plays a major role in steps 3 and 5, and most likely in step 4 (this could also be executed with pigments ground in oil alone). It is also evident that thinking about the entire coating in terms of only “the varnish” will frustrate all our efforts to gain a better understanding of it.
Basic Varnish Technology
It is important to be aware that classical varnishes were not formulated with the aid of the following terminology. Those who made and/or used them had a fairly different way of perceiving the world and explaining it‘s workings. Alchemy had a huge influence on scientific thought until at least the end of the 17th century. It has it’s own system of reasoning, with its roots in a different era of our history when the material and the spiritual were not yet separated by the ratio. At various periods during their long history, Alchemy and Alchemists were well respected and certainly not as controversial as later periods have made them out to be. Cennino e.g. openly writes that even the friars used alchemical knowledge for the making of certain pigments.
Craquelure, Cratering (or pinholes), Wrinkling, and the Chipping of varnish layers. Although aesthetically pleasing, these are technical failures that can provide us with valuable clues needed to have an educated guess at the composition and application procedure of the varnish. As are (the absence of) application marks like e.g. overlapping layers, varnish runners, standing brush strokes, the creeping of varnish into corners etc. You could compare these to the tool marks that we look for to deduct which tool was used or method was followed for the woodwork.
These clues are all caused by one or more of the following ABC :
A -The Application procedure Application method
Application sequence – how many layers
– at what interval
– under which conditions
B -The Composition of the varnish
A and B are directly related and both have to take into account the system by means of which the
varnish dries (see B2)
C -The Exposures the varnish has been subjected to after drying
Application procedure (A)
Method : For historical coatings only two methods of application come into consideration.
1 The good old brush. For this you need a medium to low viscosity varnish that does not
drag on the brush and has a “low tack” (see B2)
2 The just as good and arguably much older tampon printing (stamping) method.
Regardless of being executed by hand-palm, fingertips, sponge, or leather ball, the principle
is the same. After each new printing operation when the tampon is lifted from the imprinted
surface the varnish layer is split exactly into two, guided by fixed mechanical forces that are
the result of the composition of the varnish and the working temperature.
With this last method a very strong coloured varnish can be spread evenly and thinly, provided you use a fairly thick varnish. Any solvents used must be those that evaporate slowly (I find turpentine already too fast). It is more time-consuming than brushing and can be a little tricky at first. But it‘s advantages are in many cases well worth a try. Today’s paint rollers work on the same principle and varnishing by means of rolling a sponge under the hand was already practiced in the 15th century.
Sequence : Other than that there are at least three differing compositions used (primer, ground and varnish) nothing precise is known about this. But if we would get to know more about the nature of each composition, practice and common sense could teach us a lot about the number and thickness of layers and the drying times needed. By finding out e.g. the approximate composition of the ground layer, practice can teach us how many coats of this compound we have to apply to reproduce a certain thickness of ground.
Composition of the varnish (B)
When a varnish is formulated these days, it is common practice to set up a profile of the composition before the first tests are done. This is used as a guide to the ingredients.
The profile is based on two sets of qualities, that are of equal importance!
1 – The qualities that you want from the varnish after it has dried.
2 – The qualities that you need of the varnish before it has dried.
Both have to take the “Application method” and “Drying system” into account (see above and below)
1 – Qualities of varnish after drying
Transparency (compatibility of ingredients)
Gloss level (smoothness of the surface)
Colour (this is rarely an issue in modern varnishes)
Thermo plasticity (temperature and pressure resistance)
Chemical resistances (to solvents, alkaline, and acids)
UV degradability (resistance against yellowing, for outdoor uses mainly)
Adhesion (to various substrates)
All of these influence the Scratch-resistance and Wear-resistance of the composition.
2 – Qualities of varnish before drying
Tack (stickiness) influences e.g. the Adhesion to other materials and
the Cohesion within itself (tendency to pull threads)
Flow (ability to spread itself evenly)
Structure lack of structure or body can cause a varnish to sag (slowly give
way to gravity) resulting in varnish pile-up or even runners
Surface tension High causes varnish to pull together
low causes varnish to creep into corners
Setting speed Time to touch- or dust-dry; this is very important for the
manoeuvrability during application
Drying speed Time to sand-dry or to over-varnish ability
Drying system : There are three relevant types of drying for conventional varnishes. Most varnishes will exhibit more than one of these and this is often a cause for imperfections in the dried varnish film.
1 Absorption drying : The solvent is absorbed by the substrate or a previous varnish layer.
Usually only of importance in the first layer, or when a very easily soluble
resin has been used in the previous layer.
This type of drying will encourage fast setting.
2 Evaporation drying : The speed of this drying is directly related to the evaporation rate of the
solvent used. The faster the solvent, the less manoeuvrable the varnish.
3 Oxidation drying : Various molecules in the varnish are linked together into a more or less
coherent network through the addition of oxygen. This will go fastest where
the exposure to oxygen is greatest. On the surface!
Most of these qualities are interdependent. For example, if you change the viscosity of a given varnish with a solvent, both the “Tack” and “Flow” characteristics will change. This in turn could have an effect on the “Gloss” achieved, and more solvent will mean a slower “Setting speed” but the thinner varnish layer applied will make the “Drying” faster. To make things even more complicated; most varnish ingredients will influence several of these qualities at the same time.
On the bright side; after considering all the technicalities, today much like 100 or even 500 years ago the decisions about which ingredients to use in a formulation are still largely based on experience gained through trial and error. This of coarse requires a high degree of familiarity with the ingredients used and the manufacturing process.
I used to wonder how medieval varnish makers monitored their processes for cooking oil-varnishes without the aid of thermometers or clocks. When cooking varnishes in larger quantities however, it becomes easier to sense what is happening in the cooking pot. An experienced varnish maker can judge temperature and the stage that his “brew” is at by the way in which the oil moves on and below its surface, by vapours coming of the surface, or even by odour changes during the cooking process. Cooking times were occasionally indicated in a certain number of prayers. But even this becomes of lesser importance as experience take’s over, and in the end varnish making is much like any other cuisine.
It requires more than a good recipe to produce something that is beyond edible.
The ingredients used in varnishes can be divided and subdivided into three main categories, based on their main contribution to the overall composition.
1. Film formers Hard Resins, Soft Resins, Drying Oils
2. Transport vehicles Drying Oils, Terpenes and Essential Oils, Mineral Oils
3. Modifying agents this is a large group of additives that can even at low percentages
have a significant influence on the performance of a varnish.
It includes many different ingredients e.g:
Siccatives, Plastisizers, Fillers, Waxes, Antioxidants, Colorants
Fillers do not just add to the bulk of the varnish, they can also significantly change the drying speed simply because, as a percentage, there is less varnish in a coat. They can substantially improve the
hardness and wear-resistance, and prevent dripping. Even when colourless, they can enhance the colour of the varnish by acting as spreaders in between the colour particles (notably when pigments
are used). All of this depends of course, on the type of filler and the amount added.
A varnish that holds particle matter (pigments or fillers) is technically speaking a paint.
These days for each one of the individual ingredients, sets of standardised tests results are made available by the producers. For a resin these would for instance include data on: solubility, melt-point, compatibility, hardness, molecular weight and chemical structure.
Early varnish makers had a different way of perceiving the function of their materials, but the practical implications of their choices were the same as they are for us. Because of the smaller scale of operations they had a much closer physical contact with their products, making up for the supposed “lack” in theoretical knowledge with practical know how.
Each of the separate ingredients used in a varnish will contribute either to the way it handles when applied, to the way it dries, or to the way it behaves when dry and starts to wear. And vice versa, the way in which a varnish wears under more or less known conditions, such as sweat, friction, knocks and abrasion (or indeed the absence of these in relatively untouched areas) can tell us something about its ingredients. Just as the way it is applied can tell us something about its handling characteristics.
If we apply this knowledge to classical varnishes as a group, it is quite easily seen that the ingredients used in the top varnishes must vary, as here there is a great deal of variation to be observed. Not only in the colour, transparency, hardness, and thickness of the varnishes, but also in the way they behave when ageing. Some varnishes wrinkle up so much so that islands of varnish are formed
Some varnishes chip away from the wood, some show signs of cratering (pinholes in the surface), and there can be craquelure of all kinds. Some varnishes wear away gradually, while others get pushed around by heat and friction. And some varnishes show several of these behaviours at the same time.
What factors do classical varnishes have in common that allowed us to categorise them as a group in the first place? There are of course the optical qualities, but these are mainly caused (as argued above) by the primer possibly aided by a sealer. Then there is the ever-present ground-coat.
Again; although certainly an important part of the classical coating, this is usually quite distinct from the varnish proper. Hardly ever mentioned is the fact that no matter how rough the woodwork underneath, even when bordering on the grotesquely brute, classical varnishes are always very well applied.
Even the strongest coloured coats are equal all over in colour strength, the coats seeming simply to have fallen over any roughness in the woodwork like a blanket of snow. Scratches in the woodwork often only become visible as darker lines because the surrounding varnish has worn away. Never do we see any evidence of overlapping coats, dripping of the varnish, and very little creeping into corners and low spots occurs. Personally; I have never seen any brush marks or brush hairs on a classical instrument, nor any other fault that could have been ascribed to the actual application of the varnish.
This means that however different their ingredients might have been, classical varnishes did have one thing in common; they were relatively easy to apply. This we can feed into the list of “qualities of varnish before drying“ and in turn set parameters for the ingredients used. The varnish must have had a good tendency to flow and even itself out. It must have had a slow setting speed, giving lots of time for it to be spread evenly so any solvents used must have been slowly evaporating.
The wrinkling of a varnish surface occurs almost exclusively in oil-varnishes when the coat applied is too thick, the varnish dries too quickly, or not enough drying time is observed in between layers. Cratering or pin holing is a well known defect that often befalls coatings. This usually also stems from the top of the varnish layer drying the fastest, but only if there is a solvent present that is prevented from evaporating by the already closed surface. In time this will find its way out and leave a crater in the surface. Naturally slowly evaporating fractions of balsams could also be the cause, as indeed solvents released from previous coats. It is also worth noting that pinholes occur most often in places where the wood is more open. E.g. along the flame on heavily figured maple. Here fugitive parts of previous coats have sunken in deeper and were obviously locked in by the following varnish layers.
With all of this in mind there is in my opinion only one class of varnishes mentioned in historical sources that could fulfil all these requirements, these are Vernice Liquida type varnishes.
Vernice liquida is not a single recipe but the idea of liquefying resins in drying oils.
A historically correct translation for the term should be liquid resin and not liquid varnish, as it originates from a time when the word vernix meant resin. This in part explains why contrary to what one might expect Vernice Liquida recipes should result in fairly highly viscous varnishes.
The differences between traditionally made Vernice Liquida type varnishes and later oil varnishes are mainly caused by differences in the preparation of ingredients (most of which are basically the same), formulation criteria and cooking methods. When properly made, Vernice Liquida type varnishes will form extremely tough but flexible varnish films that are soft and warm to the touch. This and their fairly slow drying rate caused their disappearance in the middle of the 18th century. The general taste for finishes had by then changed to hard and glossy. Some of the higher quality Vernice Liquida recipes result in varnishes that exhibit the typical ivory yellow fluorescence of “classical grounds” under UV light. When pumice powder is milled in, these can be turned into a gesso type ground that provides stability beyond compare.
It would have been in accordance to the at the time prevailing practice for a 16th or 17th century craftsman to buy this varnish ready made at his local apothecary and modify it according to his needs, by adding oils, resins, colours, or even other varnishes.
This hypothesis could explain both the strong sense of similarity and degree of variation in varnishes from the same locality, while allowing for overall easy application characteristics.
0 Claire Barlow, “Firm Ground” (parts 1 and 2) ;The STRAD March and April issues 1989
see also The Catgut Acoustical Journal, November 1989
1 Cennino d’Andrea Cennini, “Il Libro dell’Arte” ; translated by Daniel V.Thompson Jr.
Dover Publications New York (ISBN 0-486-20054-X)
Below is an explanation of the use of the Byzantine system for violin coatings.
We believe that the Byzantine finishing system was the theoretical basis for classical violin makers when it came to varnishing. In principle the same method had been used for centuries, whether executing tempera and oil-paintings or decorating all kinds of other objects. Because it was so firmly imbedded in the cultural heritage of artists and craftsmen alike. It was the most logical and possibly even an unquestioned method to follow for any woodworker when it came to varnishing. The main difference for violins was that unlike in decorative paintings, the total coating had to be transparent because the carrier – the wood – plays a crucial role in the appearance of the finished work.
Arguments to support these opinions are given on the “Additional info” page of this site.
* The Byzantine finishing system *
This consists of five steps, the purposes of which are:
To prepare the substrate so that it will accept the coating and to improve specific substrate qualities.
This does not necessarily imply that any substances are applied to the substrate, sometimes simple smoothening operations were considered enough.
The classical violin primer gave the wood it’s golden colour, but this was only a side effect.
The main reason to use primers like our Imprimatura Dorata would have been to harden the wood, protect the fibre against wear and dirt, increase it’s transparency, and to maximise the amount of reflected light.
To take the “hunger” out of the substrate, so that the ground will not sink into it excessively.
In the case of classical coatings it could also have been used to increase the translucency of the wood by raising it’s refractive index and to give the fibre some extra protection. A sealer should never! take on the role of a ground.
In classical coatings it is the ground that fills the pores of the wood, not the sealer.
If at all, this should be present only as an unnoticeable layer
To provide a stable and even foundation for the actual painting.
Even should be interpreted not only as in smooth, but also even in it’s acceptance of paint or varnish.
The key and central role in the Byzantine system is performed by this third step, the ground.
It is the transparent version of what is referred to in painting as the “gesso”
In a very real sense it must have been understood to be the foundation that gives stability to the entire coating.
Once we have accepted that the classical ground – because it is transparent – must be basically an oil varnish (be it a very special one) with filler material, many materials could be considered as candidate for a transparent filler. If we realise though, that transparency is only a specific requirement for classical coatings but the essence (and original purpose) of a ground is to provide stability and evenness, the candidature is narrowed down considerably.
To apply colour or an image. If a varnish holds particle matter it is technically speaking a paint.
So in reality many classical violins are not varnished at all, but painted first and than maybe varnished.
Our habit of talking about classical coatings as varnishes, causes us to think about and classify them as such. This limits our willingness to consider anything that is not runny and brush able.
A large proportion of the colour seen in many classical coatings we believe to be caused by pigments.
Thinking about the execution of at least this coloured part of the coating as painting, will enormously expand our possibilities to create variation. Recreating the intense and luminous colours of especially some later Cremonese instruments and doing this in as thin a layer as is sometimes evident, almost certainly required the use of very highly pigmented “paints“. Applying these in even layers over a relatively large surface would have been (and still is) a lot easier to accomplish by tampon printing method than with a brush. At the start of the classical period this method had already been used for centuries to execute the final varnishing of paintings. In the case of tempera paintings this final varnish layer was often a Vernice Liquida Comune.
To protect the painting from outside influences (moisture, dirt) and equally important, to even out differences in the surface texture.
In historical painting methods different pigments sometimes required different media. Also early paintings were often made by using a variety of techniques and materials in one painting so evening out was important.
* Standard varnishing procedure *
In the information sheets that accompany our products, we suggest many variations on the Byzantine system. This could easily have the effect of marginalizing the importance of the system as the central framework for all of these variations. In the Byzantine system (or any varnishing method) every step and the way in which they are executed are related to the outcome of the finished coating. Variations on and shortcuts through this system can be made, but in my experience they are much more successful and educative if they are made with the system in mind.
Using this system and the information that accompanies our products, a good working sequence to get familiar with before you start improvising would be the following:
0. – Finish the instrument in the white with scrapers and burnish the wood with shaving grass.
1. Primer – Apply 2 coats of primer to the pine and 3 coats to the maple.
2. Sealer – Apply 1 coat of sealer to the entire instrument. Hang the instrument in a warm sunny
place or a drying cabinet (for about 12 hours) immediately. Then leave it in a warm airy
environment (preferably outdoors in a semi shaded area) for another 4 days.
3. Ground – Grind 30 – 50 % pumice powder into Vernice Liquida Comune (10 grams of varnish will
become 13 -15 grams of ground) and apply 1-2 coats. Three or more coats will become
clearly visible as an uncoloured layer underneath the coloured varnish.
This ground can also be rubbed into the wood only.
4. Painting – Grind up pigments into a Doratura type varnish (or V.L.C.) and apply this paint by tampon
printing method to your instrument. If you do (for whatever reason) want to use a brush
and find that the varnish doesn’t work very well, consider changing the brush before you
start to change the varnish. The ratio of pigment to varnish can vary. 1 : 4 (by weight) is a
good average. At first it may seem impossible to work this much pigment into the varnish.
To start of, mix the pigment in with a small spatula until you get something of a dough like
consistency. Then grind small amounts at a time between two flat surfaces (now your
paint should become a little more liquid again) Finally mix these small amounts together
again thoroughly, after having added the dryers. If your paint is too thick or dry it won’t
apply easily. Add more varnish. You want to end up with a thick honey like paste that is
only slightly sticky. This may seem like a lot of work at first, but you will only need around
7 grams of strong paint to cover an entire violin and you can apply all of the colour in 1 or
2 coats. If you want to use a solvent, use old fashioned (non perfumed) petroleum (lamp-
oil) but use it very sparingly. A few percent will already decrease the viscosity of the paint
notably. In some countries this mineral oil distillate is known as paraffin or kerosene lamp
oil. White spirit is a safe substitute but a little faster evaporating. If you are using only a
low concentration of pigments, or your coloured varnish holds no pigments
(like our Doratura Varnishes) you can decide to skip the next step.
5. Varnish – Finish the process with 1-2 coats of Vernice Liquida Comune. Leave alone for about
2 weeks with enough sunshine or the equivalent hours in a drying cabinet.
Hang the instrument in a warm, dry and airy environment in between sunshine sessions.
This step can also be executed with Doratura Rosso or Doratura Cremonese
Now do your final polishing (if needs be) after which you can start the fitting up.
Polishing can be done with ever finer abrasives until you reach a fineness that actually leaves a shine, or by changing over to French polishing (with only oil and alcohol) at some stage during this process.
French polishing Vernice Liquida type oil varnishes becomes easier as the varnish films mature. Alternatively one last strongly diluted layer of Vernice Liquida Comune can be applied with a soft brush.
Give this coat another few days to dry!
Unlike violinmaking which can benefit from a certain amount of panache in its execution and an ad lib. attitude towards the original plans, varnishing should be approached methodically and with patience.
There is an old rule of thumb which says that ”the longer you take for your varnishing, the longer it will last” This of coarse has it’s practical limitations, but in general varnishes (and specifically oil varnishes) are not improved by haste. If you are really in a hurry, think about how you can cut the number of coats (before you start !) rather than cutting on the drying times, or send your customer an apologetic letter to excuse the bad weather.
We all have our own history of struggle with varnishes. What we struggle with becomes part of us.
It is therefore unavoidable that a sense of personal integrity surrounds the coatings that we apply to our white instruments and the methods we use to do this. At the same time though “our” white instrument first entered the workshop as wood from so and so. Similarly; if we receive new information and work with it, there will unavoidably come a point where we can and will regard this information as our own. Knowledge about a certain subject does not grow out of gathering 2nd and 3rd hand information, but out of personal struggle with that information.
* The tampon printing method *
Historical Vernice Liquida type varnishes were designed to be applied by tampon printing method.
This method should result in thinner layers of varnish being applied than brushing could achieve, but there is no shrinkage from solvent evaporation and each varnish layer can be very strongly coloured.
After some practice you will find it easy to produce a miraculously uniform coating with this method.
1 thin layer of varnish on a violin will contain 2 – 3 grams of Vernice Liquida type varnish.
1 thin layer of varnish on a cello will contain 10 – 15 grams of Vernice Liquida type varnish.
A high estimate for the total amount of Lacca Rubia pigment used on an instrument is:
Violin 1 ½ grams
Cello 6 grams
_ Dab the varnish onto the instrument with a stiff brush as evenly as you can.
– Next with an almost dry softer brush gently ‘’tap’’ varnish into the tightest corners of the edgework
and scroll. These areas can be difficult to reach, even when using your fingers (the preferred tampon
material for these areas).
– Now gently press your tampon alternatively onto the fattest and leanest covered areas, going al over
the instrument. You can ‘’print’’ on the same spot as often as you need or like to.
About 2 impressions per second is an average speed and still manageable on larger instruments.
The fleshy areas of the human hand palm and ring finger are perfect tampons and have evolved
especially for this Purpose. When done, you can clean the varnish off your hands easiest with soap,
alcohol and a nailbrush. With each consecutive printing operation the varnish layer is split into two.
Ultimately the viscosity and tack (stickiness) of the varnish will force the layer to become perfectly
even all over.
– Do not add any solvent once you have started varnishing!
Variation in viscosity will cause variation in tack this in turn will result in uneven layer thickness.
– Vernice Liquida thinned down with fast solvents can be brushed on initially and tamponed to
perfection after the solvent has evaporated.
– You may need 5 – 15 % of solvent to reach a good brushing viscosity, depending on brush stiffness.
– Do not thin the varnish down too much or it may run, remember that you will tampon away any brush-
Marks later and that the varnish will level out in the sun.
– Preferably use a high quality house painters brush for this
With a slower solvent (e.g. petroleum) tamponing can be done at any stage.
– Be careful not to apply the varnish too thickly (as this could be easily done) If a layer is applied
too thick “orange peel” effect and ultimately running of the varnish may be the result.
Also high temperatures during drying may then cause the varnish to run.
To avoid this, start of with too little varnish. You can always add more while you are tamponing.
You can also pre dry varnish in the shade or grind in transparent filler materials to avoid temperature
induced running. If the varnish stands up in little droplets or the wet surface is very slippery you have
got too much varnish. This can be removed with some cloth, or by tamponing the excess onto a still
unvarnished part of the instrument.
– Brushes used for the initial application should be more like short glue brushes than like varnish
brushes in stiffness. Brushes used for tapping the varnish into tight spots can be softer and springier.