French Polishing Notes
This is a summary of the course content
Health & Safety
When sanding timber surfaces, particularly hardwoods, always wear a dust mask to avoid breathing in dust.
Shellac flakes are dissolved in IDA which is denatured alcohol (clear methylated spirits). This industrial alcohol is toxic and must never be ingested. Wear tight fitting vinyl gloves to avoid getting it on your hands. Always work is a well-ventilated room.
What is French Polishing?
French polishing is a method of applying varnish (in the form of shellac dissolved in alcohol) to the surface of wooden items, using pads or ‘rubbers', rather than brushes.
The essential materials used for French polishing are:
shellac
IDA (industrial denatured alcohol, commonly known as methylated spirits)
rubber (an absorbent pad made from wool and cloth)
oil
The process is all about developing a way of applying the liquid to obtain a smooth, level surface.
The method of preparing the surface differs depending on whether the object is new wood, with level, smooth surfaces, or alternatively an old, perhaps antique piece of furniture, which most likely has uneven surfaces, historic damage and other irregularities which are seen as a virtue and which we should not try to remove. The amount of sanding back, and flattening will be adjusted to suit the type of surface; the distorted, uneven surfaces that are often found with old veneered or marquetry work will not be flat, and we cannot attempt to flatten them without destroying the history of the object.
Shellac is an extremely versatile material. In its simplest application, it can be used as a sealer on bare wood, protecting the surface from dirt and giving a low-sheen finish on its own, or it can be a base for a wax finish (wax should never be applied to the bare timber – always seal with shellac first).
But if a deeper sheen is wanted, a number of polishing sessions can be completed with shellac, bringing the surface to a satin finish, and worked until there is a deep glow emerging from the wooden surface.
Finally, a fully French polished ‘mirror’ or ‘piano’ surface will be obtained if the layer of shellac is built up sufficiently to allow polishing to a high gloss finish.
(French Polishing, as a ‘wood finish’, should not be confused with other finishes such as waxing and oiling. To some extent, these materials can be used together; for example, it is common in the antiques trade for furniture waxes to be applied on top of dried shellac. But this is NOT true French Polishing. The beauty and logic of a French polished surface is that the skilled application of shellac can produce a smooth, clear and clean surface – this can always be ‘touched up’ later if minor scratches or damage occurs. Once wax has been applied on top of shellac, not only does it obscure the clarity of the surface, but it is not possible to apply more shellac later, without first removing every trace of wax.)
Varnish, applied by brush, or a modern sprayed-on lacquer, tends to look like a separate covering sitting on the surface. With French polishing we try to ‘cultivate’ the surface so that the wooden object and the surface material appear to be organically connected – as if the deep glow, the patina on the surface, emerges from the wood underneath. This is difficult to explain in words, but becomes clearer when seen.
With period pieces, it is worth checking first if the existing surface is actually sound, and simply hidden under years of grime, dirt, dust and layers of wax.
Sometimes all that is required is a good clean, which may reveal that the surface is in good condition. Much of the value of an antique object is in the original surface patina, and this should not be disturbed unnecessarily. Start with the least intrusive cleaning – water with a drop of washing up liquid may do. If not, a proprietary wax remover fluid may work. Polish revivers / burnishing creams can then be used to bring back the surface to a good glow. But often this is not enough - if the surface is too damaged to respond to cleaning, then proceed with re-polishing.
Stages of French polishing
1. Start with a clean smooth surface
2. Seal surface with a coat of shellac and rub down when dry
3. Fill pores if desired
4. Two to six bodying sessions may be needed
5. Polish
6. Burnish
Now in more detail:
1. Start with a clean smooth surface
New wood surfaces: It is important to begin with a surface that is clean and smooth. New wood needs to be sanded with various grades of abrasive papers, in sequence. Usually 150, 180, 240 and then 320 grades will give a good result. Recommended abrasive is silicon carbide stearate coated paper.
Old wood surfaces: This may need more preparation – old shellac can easily be removed by rubbing generous amounts of methylated spirits on with very fine steel wool (grade 0000) and wiping off with rags. Repeat until clean. Paint strippers may be needed for some types of varnish. Stripping is better than deep-sanding as it does not alter the wooden surfaces, edges and profiles. Over-sanding can round everything over and there is a loss of definition and the history of the piece is destroyed.
Once the shellac / varnish has been removed, you may still need to sand the surface to achieve a smooth surface. Surfaces on period furniture should be treated with care, so as to leave as much of the original history in place as possible; a compromise between wanting a perfect surface, balanced against the wish to retain the identity of the object.
Ideally, we would simply clean old wax and grime off an antique surface and then lightly French polish in order to retain the patina and history. But in reality, a lot of furniture that comes for restoration is too damaged and we need to clean off and re-polish. The skilled French polisher aims to produce a surface that appears well-looked after, rather than brand new. Once the surface is clean, vacuum with a soft brush attachment to remove some dust from the pores and then use a soft cloth and IDA to rinse or wipe off remaining dust.
Summary:
Remove old shellac / varnish
Sand
Rinse off dust
2. Seal surface with a coat of shellac and rub down when dry
The clean surface now needs a couple coat of shellac to seal the wood and provide a sound surface for later applications of shellac.
Flat surfaces:
These are best sealed with a French polishing rubber, not a brush. Rubbers produce a smoother surface. Brushed-on shellac will most likely need a lot of sanding to make level.
Load a rubber with shellac, mixed to the standard ratio of 250g : 1000ml.
Squeeze out any excess onto clean paper. Shellac made with good fresh shellac flakes and IDA should be touch-dry almost instantly; 99% IDA evaporates fast as there are almost no impurities. The sealing coat can be repeated two or three times. When wetting the wood for the first time, the fibres that were laid flat by sanding, tend to stand up and the surface may feel fuzzy and less smooth than before, so after 30 minutes, rub down with a finer paper than used before, such as 1800 Micromesh. The surface should feel smooth and silky. If not, it will help to repeat the sealing coat again, wait till dry and rub down again. This can be repeated any number of times until the surface is as perfect as possible. It may be necessary go back a stage and sand with finer grades of silicon carbide papers used earlier.
Curved, turned, carved surfaces:
A soft varnishing brush or mop will deposit shellac into the grooves more easily than a rubber. It is important, though, to dilute the shellac about 60/40 shellac to IDA and to apply sparingly. Thick shellac will be too viscous and syrup-like when applied by brush - more like a thick varnish rather than French polish.
Summary:
Seal with shellac
Rub down
(repeat several times)
3. Fill pores
Wood with a naturally open pore structure may be treated with a grain filler if you want a perfectly smooth, glass-like finish, without any of the texture that is visible on the natural surface. In the past, this was often done on high quality, usually small objects, but was rarely the case for large areas like wall panelling. There is a certain appeal in leaving the wood with a degree of its natural texture, so this is a matter of personal preference. Both unfilled and filled surfaces can look good.
If pore filling is to be done, then the surface should first be sealed, as described in stage 2. above.
There are two common methods of filling pores; either a paste containing tiny particles can be rubbed in, or pumice powder can be used to generate wood dust that is worked into the pores.
Paste grain fillers:
Most paste fillers are coloured to match the darkest part of the wood (or pigment can be added to alter the colour). A few are now available that are truly transparent (such as ‘AquaCoat’); these dry invisibly so no pigment is needed. Follow the directions given with the product. Usually the filler is rubbed over the surface and then the excess is removed. Three or four applications may be needed before most pores are filled. Except for the transparent filler, the others all need a few coats of shellac underneath, to prevent the colour of the filler from staining the surface of the wood. The aim is to fill the pores and leave the main surface untouched.
Pumice powder:
It is common to see the pores in old mahogany surfaces filled with tiny white specs. This is because during the 19th century it was common for French polishers to use plaster of Paris as a filler. The particles are small and easily go into the pores. The natural white colour of the plaster was changed by adding a suitably coloured pigment to the mix, to match the wood. Unfortunately, over time, sunlight can bleach out the pigment if it was not light-fast and then the pores then the original white colour of the plaster is visible in the pores.
Sometimes the process of cleaning old shellac off the surface prior to re-finishing, can itself remove pigment from the plaster filler. There is no easy solution to this problem. Trying to stain the plaster filler may dull down the plaster colour, but often the wood itself becomes even darker, so the contrast is still evident. The lesson for now is to make sure that you use a light-fast filler. Pumice powder works because it tends to go translucent when soaked with IDA and in addition, the aim is to use the abrasive nature of the pumice particles to generate fine wood dust from the surface, which, mixed with the small amount of pumice, is worked into the pores and so the colour matches the wood.
Start with just one coat of shellac as a sealer. Then make a small pad from some wool, covered with a piece of cotton cloth. Apply some IDA to the pad and dab it onto a small amount of pumice, then soak more IDA onto the pad. Now begin rubbing in small circles. The IDA will soon soften the sealing coat of shellac and start to generate dust from the wood surface. As the rubbing continues, the mixture of pumice, dust and shellac is forced into the pores. Work on an area of about 10cm square at a time, for a few minutes, then move on, reloading with pumice and IDA when the grinding sound is no longer heard.
There should be no build-up on the surface – the filler should only go into the pores. Any build-up suggests that too much pumice or shellac has been used, and it is best to try and clear it off with more IDA. Aggressive sanding tends to remove the filler from the pores and can introduce light coloured dust into pores as well. It is usually necessary to repeat this filling stage with pumice three or four times before the pores are filled; small pores on wood like mahogany or walnut are easier to fill than those on oak or rosewood. Some pores are so large that it may be more effective to use a paste filler first, followed by pumice later on.
In recent times, other materials have been tried, including various resins and epoxies and even superglue, but these can be unpleasant to use due to fumes and require excessive time spent sanding down excess filler left on the surface.
Summary:
Seal with shellac
Apply filler several times
Rub down lightly
Seal with shellac
Repeat all steps several times
4. Two to six bodying sessions
Now that the surface is smooth and sealed (with pores filled if desired), the gradual process of building up a covering of shellac is begun. Once a sufficient thickness is achieved, the upper surface of the shellac can itself be polished to produce various degrees of satin, gloss or a mirror-like reflection.
It is essential to have a light source from the opposite side of where you are standing, with light falling onto the work, so you can see what is happening. Light from above does not help, nor does too much daylight flooding in directly by a window. You need a clear pool of light falling onto the surface.
Depending on the size of the rubber, use 6 to10 drops of IDA to wipe across the surface just before starting, as there will be some dust that needs to be removed. ( A temporary cloth placed over the rubber will pick up the debris and avoid it contaminating the main cover.)
Now load the rubber itself with Shellac. For bodying, the initial mixture of shellac and IDA (250g :1000ml) needs to be diluted with IDA. A ratio of 5:1 (shellac : IDA) is the proportion to start with. This can be adjusted to suit you. Some find they prefer a thinner mix, perhaps 3:1 (shellac : IDA). Too-viscous shellac will be difficult to apply smoothly and level. Swirls are likely to set into the surface. But if the mixture is excessively thin, there will be a lot of IDA to evaporate, after which there will only be a minimal covering of shellac on the wood.
Once the rubber has been loaded, always squeeze it down firmly onto a sheet of clean white paper and repeat until the impression left on the paper is a clear wet mark, with no pooling of shellac around the edges. If the mark is speckled, with dry paper showing within the shape, it is too dry. The shellac needs to be saturated right into the wool inside the rubber, so that it functions as a wick, feeding shellac constantly through to the surface.
When the degree of wetness is right, add two to four drops of mineral oil onto the rubber. Oil is needed when there is a danger of the IDA in the pad over-softening or dissolving the previously applied, dry shellac. Remember that IDA is always a solvent for shellac. These few drops of oil lubricate the rubber, allowing the new, wet shellac to amalgamate with the shellac below, without dragging and damaging it. The oil is all removed later on, so it is important to understand that the use of oil in French polishing is very different to the function of oils intended to be worked into the wood surface itself, such as kitchen worktops, cricket bats or furniture, where Danish oil or linseed oils is used. In French polishing we prefer a non-drying oil like mineral oil so that there is no danger of it drying on the surface prior to removal.
The newly-loaded rubber is first moved across the surface, taking off and landing, just like when sealing the surface earlier on. This distributes the new mixture and the oil over the surface, and reduces the danger of creating any swirls of shellac from the wet rubber. Once the surface has been covered in straight lines, begin a logical sequence of movements so that the shellac is distributed evenly; rows of circles, about 10cm in diameter, can be worked along the surface, and immediately work another row beneath the first one, with a slight overlap. Continue across the surface, until it has all been covered and then go back to the beginning and repeat. Rows of circles can be alternated with long straight lines from one end of the surface to the other, ensuring that the turns at the ends are always curved, so that there is no danger of the rubber stopping for a second.
This is like a long figure-of-eight shape on its side. The rubber must never stop moving while in contact with the surface. Lift it off or on like an aircraft landing or taking off, never like a helicopter moving up and down vertically. As the rubber moves along the surface you should start to see what French polishers call a flash or mist or cloud – this is caused by the IDA evaporating instantly and passing through the film of oil. If this mist is not obviously visible, it means that the solution in the rubber is probably too viscous. You need to stop and add another six drops or so of IDA onto the rubber and another drop of oil.
Carry on moving the rubber over the surface and the instant flash of mist should be visible. If a jar of shellac is left open the IDA will gradually evaporate and the shellac will thicken; temperature and humidity also affect how the polishing process works. This is why a little adjustment of the IDA / shellac /oil solution may be needed at the start of a bodying session.
As the rubber dries, the cloud will become less pronounced. For practical purposes, the easy way to see how dry the rubber is, is to push it down firmly again onto a sheet of paper. If almost no impression is made, you need to re-load the rubber with shellac and IDA, push down on the paper again to remove any excess, add a drop of oil and carry on bodying. As a guide, a surface 60cm x 60cm can usually be bodied for about twenty minutes, re-loading the rubber whenever it dried out. Finally, when you decide to end the bodying session, move the rubber over the surface in straight lines for a few minutes to try and avoid any cross-grain swirls being visible.
Stop and add about six drops of IDA to the now-dry rubber and move it across the surface in straight lines. This process of Cleaning and Flattening has two aims; this extra IDA will help to flatten any small ridges of shellac that you may have introduced to the surface. The IDA will also remove some of the oil. Repeat cleaning with a few more drops of IDA and repeat two or three times. Finally, place a clean cloth over the rubber, add more drop of IDA and go over the surface again because there will be oil on the rubber and we want to remove as much oil as possibe. If the surface-gloss appears to diminish after cleaning, this is because it was caused by the oil film and is not the true shine of the shellac.
Failure to remove most of the oil at the end of the session will result in many small dull spots appearing on the surface an hour or so later. This is not a problem, but is a sign that you need to clean again to remove them. This is often done after a break of an hour, when the oil residue is clearly visible.
Now leave the object to dry for at least six hours. Although up to three bodying sessions can be done per day, it is better to only do one in a day so that the surface dries properly before carrying out the next application. Shellac is touch-dry almost immediately, but it takes much longer to harden properly.
When you are ready for another bodying session, it is important to first clean the surface again. Some atmospheric dust will have settled and become embedded into any remaining oil, making it impossible to simply wipe or blow off.
Place a temporary cotton cover over your rubber and apply a number of drops of IDA. Clean the surface as before. Repeat as needed, until the surface is clean. You might be surprised how much dust is now on the bottom of the rubber.
Providing the surface now appears clean and smooth, proceed with another bodying session, just as previously. (The need to rub down the surface with abrasive paper between sessions only occurs if you have introduced grit or ridges of shellac that spoil the smoothness of the surface. If you decide to rub down, a fine abrasive such as 1800 Micromesh or 400P paper should do. Clean the surface with IDA after sanding.)
You should always carry out at least two bodying sessions, preferably one per day, as the first coating can sink into the wood fibres overnight and appear patchy later on. Up to six sessions may be needed if you are aiming to polish the surface to a high gloss. The number of sessions needed depends on the effect you want and the amount of shellac you add during each session.
Once you think the surface has the depth you are looking for, a final short bodying session may be done, using a more dilute solution of 2:1 (shellac : IDA) and then the bodying is over and nothing should be done for at least two days while the shellac hardens.
Although a satin finish, with a soft focus reflection will be evident after one or two bodying sessions, a deeper, fuller gloss or mirror reflection requires a thicker coating of shellac.
Rather than build up, for example, four sessions at a ratio of 5:1 shellac to IDA, an alternative method is to body up with increasingly more dilute solutions. You might carry out six sessions, starting with a 5:1 mixture for the first session and changing each session thus: 5:1, 4:1, 3:1, 2:1, 1:1.
As the solution becomes more dilute, the more glossy result is evident.
The final couple of sessions are achieving a similar result to the Polishing stage described in the following step.
Summary:
Between two and six bodying sessions
5. Polishing and burnishing
The surface of the shellac can now be inspected to see if it looks as you were hoping. There will already be a reasonable degree of satin finish, which shows as a soft focus effect if you look at the light falling onto it, being reflected towards you.
There are now several options available to finish the surface with the amount of in-focus reflection required:
Low satin finish: If the bodying itself has produced the surface you want, then all that is needed is to make sure any remaining oil is cleaned away. A rubber loaded with about six drops of IDA can be moved across the hard shellac surface, mostly in straight lines, to lift away the oil. Repeat immediately a few times, then wait an hour and repeat. If you look onto the surface while you move your fingertip across it, there should be no trace of any smear caused by oil.
Enhanced satin finish: If you want to see a slight exaggeration of the finish achieved from the bodying process, then load the previously-used rubber (which should be almost dry, but feel slightly cold when pressed onto your skin) with one or two drops only of shellac, six to ten drops of IDA and only one drop of oil. Now polish vigorously in small circles, finishing with long straight lines. Observe the result in the light. There should be an intensified reflection, but not entirely sharp. As you polish, the IDA and the single drop of oil will appear to ‘burn off’ and the surface should look clean and glossy. If you move your finger across the surface there should be no sign of any oil.
Medium to high gloss finish: A medium or total gloss finish can only be created if the shellac is of sufficient thickness so that the reflection and refraction work well. A French polished finish should only produce a thin layer of shellac, probably between 0.05mm and 0.1mm, and this is why the effect on the wood is so subtle. The shellac must also be hard. It is best to wait at least three days after the final bodying stage before polishing. Polishing exactly as described in the stage before, will, on a hard and reasonably thick surface, produce a gloss finish, where the image of a light bulb falling on the surface is totally in focus. Spiriting off any oil as before, must be carried out several times to ensure the surface is oil-free.
Mirror gloss finish: Once the surface has been left to harden for at least seven days, the gloss can be exaggerated further by rubbing a small amount of burnishing cream over the surface with cotton wool and buffing to a shine. This is the traditional ‘piano’ finis
Summary:
Polish surface with IDA
Burnish surface with cream
French Polishing Stages
1 surface preparation
2 sealing
3 (grain filling - optional)
4 bodying
5 cleaning and flattening
6 spiriting
7 polishing
8 burnishing
9 admire your work!
Materials:
Blonde de-waxed shellac flakes
IDA (industrial denatured alcohol, commonly known as meths
Airtight plastic box for storing rubbers
Fine grade pumice powder, or proprietary grain filler
Old knitted wool for interior of rubber
White cotton cloth (recycled sheet material) or ‘mutton cloth pieces’ (NOT mutton cloth)
Mutton cloth pieces from Fiddes (similar to stretchy T-shirt material). This fabric is preferred because it is softer and smoother than cotton sheet cloth and produces less friction as it move over the surface.
Mineral oil
Universal pigments
Wood filler and touch up paints
Varnish brush: 1 inch best quality sable or squirrels’ hair or similar (must be very smooth) and smaller Artists’ flat brushes
Methylated spirits for brush cleaning
Abrasive papers: 150G,180G, 240G, 320G
0000 fine grade steel wool
Wet and dry paper
Burnishing cream
Barlis of Lincoln /Jack Darcy www.barlisoflincoln.com (now taken over by Jack Darcy but the Barlis website still operates.)
https://www.barlisoflincoln.com/clarks/french-polishing-starter-kit-choose-flakes
go to www.barlisoflincoln.com and click top left: Clarks / Jack Darcy, then bottom right Starter Kits.
barlisclark@gmail.com Tel: 01427 668283
Most materials, including the best quality 'Suter' Shallac Flakes that we use on the course.
Starter Pack 1 (choose either BLONDE or SUPER BLONDE de-waxed shellac flakes to mix your own polish):
250g super blonde shellac flakes or button shellac flakes
3 x 50ml pipette bottles
300g cotton cloth
1 metre cotton wadding
50g pumice powder
100ml white mineral oil
1800 grade Micromesh (150 mm x 150 mm)
1 litre Industrial Denatured Alcohol 96% (sign form attached here)
1 spare plastic litre container
Astor and Windsor www.astorwi.co.uk
IDA (Industrial Denatured Alcohol) 99.5% (send them your authorisation form)
(IDA) industrial denatured alcohol (You need to have the HMRC letter to purchase this - application form here paragraph 19 ) Print and post the form. After four weeks if you have not received your letter, call to chase up – they are slow! 0300 200 3700
Smith & Rodger www.frenchpolishes.com/shop.html
(Most materials, including clear methylated spirits and shellac flakes)
Clear Methylated Spirits 94% (no authorisation needed)
To purchase 99.5% industrial denatured alcohol, you need to obtain (free of charge) a letter from Revenue and Customs which authorises you to purchase it. You can download the application form here (paragraph 19) , or call them on 0845 010 9000 and they will send you a registration letter. It does not take long and HM Customs and Excise and there is no cost involved. They normally refer to this product as 'IDA' or 'Industrial Denatured Alcohol'. You can purchase up to 20 litres a year.
To purchase 94% clear meths, no authorisation is required. The higher the alcohol content, the faster the shellac will dry.
Suppliers:
Barlis of Lincoln (barlisoflincoln.com)
Restoration Materials (restoration-materials.co.uk)
Rest Express (restexpress.co.uk)
Finneys Wood Finishes (finneyswoodfinishes.co.uk)
Koning wood fillers (konig-uk.co.uk)
Beares Super Nikco (beareandson.co.uk)
Astor & Windsor IDA (astorwi.co.uk)
Fiddes (mutton cloth pieces for making rubbers)
—————————————————————————————————————————————————————————————-
Application for Authority to receive and use Industrial Denatured Alcohol
Part A. *I/We (name of company, partnership, proprietor, as appropriate)
apply for authority to receive IDA………………………………………………………………………………………
for use at (address of premises):
………………………………………………………………………………………
Type of business/activity………………………………………………………….
VAT Registration Number…………………………………………………………
Part B The IDA is to be used for the following purpose(s):
………………………………………………………………………………………
Part C *My/Our estimated annual requirement is:
*Industrial Denatured Alcohol…………………………15……. litres
Declaration
I declare that the information I have given on this form is complete and correct. I have read and understood Notice 473: Production, Distribution and Use of Denatured Alcohol.
Signature…………………………………………………………………………….
Full name…………………………………………………………………………….
Status…………………………………………………………………………………
(proprietor, partner, director, company secretary etc.)
Date……………………………………………………………………………………
Phone number……………………………………………………………………
Fax number…………………………………………………………………………..
Email address………………………………………………………………………..
*Delete as necessary
Please send application to:
HM Revenue and Customs
National Registration Unit
Portcullis House
21 India Street
Glasgow G2 4PZ