Tips on Filling and Inpainting for Painting Restoration
by John Sutton
Although I could always draw fairly well and thought I could jump right into inpainting when I first started out in art restoration years ago (1982) I was mistaken. It took me at least six months to be able to do anything easily as far as inpainting went, then all of a sudden things started to click and I was off and running. Today I find it the "easiest" and most enjoyable part of the work - I can listen to music, have some tea, relax and the inpainting usually goes smoothly, and if I don't like the result I can wipe it off and start again. I also find I can do a lot more with a lot less paint after many years of experience. Being a real minimalist helps since the more of your own paint you put on a loss the more obvious it becomes.
I am happy to publish here a few hard learned tips that might help and a few other things learned along the way. I'll try to keep it simple and straightforward. I learned the basics of inpainting with "modern" materials PVAC(AYAB) from Gustav Berger in the early 1980's and I highly recommend his excellent book Conservation of Paintings, Research and Innovations available from Talas.
Also note the new (2010) Icon Paintings Group publication Mixing and Matching, Approaches to Retouching Paintings - especially the chapter by Sarah Cove of London, UK on Retouching with a PVA Resin Medium. Sarah Cove has written an excellent article on the benefits of this inpainting system.
Filling:
First the fill. I use Mowiol, a polyvinyl alcohol resin from Hoechst Chemical as a water soluble binder for whiting to make my gesso fills. See Diane Falvey's article on Mowiol as a binder: The Advantages of Mowiol (polyvinyl alcohol): Comparative studies of organic and synthetic binding media for fillers on canvas in ICOM Committee for Conservation, 6th Triennial Meeting, Ottawa, 1981. It is basically a synthetic watercolor binder and I make up a very small amount of it from the dry powder to keep around the lab. You can experiment with the amount you need and make your fills more or less "hard" depending on the painting's needs. It remains forever very quickly re-soluble in water so is very easy to remove. Interesting enough I have found that if you add too much Mowiol to your whiting mixture it becomes very difficult to work with - you end up with a soupy "plastic" instead of a nice fast drying fill. My formula is just a couple of drops for each heaping tablespoon of whiting. The dry resin is mixed 1:3 kitchen style with water to make the stock solution.
Mowiol bound gesso can be carved, shaped, or burnished flat with your finger, depending on the application and it is very easy to remove. It can also be applied with a paintbrush if this is your preference. I tend to use small very flat and very clean palette knives.
I make up a number of shades of gesso to keep on hand and just re-activate them with water as necessary. Cheap Joe's sells a handy watercolor tray with good size circular and square well s. I have three or four of these in the lab with different color fills made up and ready to go. I use powdered pigments to tint the gesso as I am mixing it up from scratch. Eyedroppers are handy tools to use throughout this process.
I try to fill to match the original ground color although sometimes a bright white will be necessary in a sky or highlight.
Seal the fill when thoroughly dry very carefully with a thinned PVAC(AYAA/AYAC) sealing varnish (thinned in alcohol) and a small watercolor brush. Sometimes two coats are necessary. Wipe up the excess from the surrounding areas with a damp cloth or swab after your sealer is dry. Be very careful not to leave a halo of excess gesso around your fills - it will look like a bloom in the painting but is actually your fill material.
Filling accurately is the really hard part and it's good to get that out of the way. The fill should be exact and perfect for your inpainting to be acceptable.*
*An important note: A lot of times if your filling or inpainting does not work out so well it is because there is Beva or some other adhesive that remains in the losses that you didn't notice. This will cause all kinds of problems in the finishing of the work if you do not remove any excess consolidant or lining adhesive from the face of the painting before you begin to fill and inpaint.
Inpainting:
My preferred medium is PVAC(AYAB) thinned to the consistency of water in an isopropanol/ethanol mix with a little touch of acetone. I mix up powdered pigments on my palette and bind them with the AYAB - enough binder to keep them on my palette but I paint basically using a watercolor technique and want to keep the colors thin and not rich. Too much binding medium makes for hot spots and these can be seen a mile away in the finished work. The way to get around that problem is to inpaint very thinly and let the varnish layers even out the gloss. I know it is difficult to color match when learning and the tendency for the beginner is to keep the inpaint "wet" with a lot of medium so you can see the colors while you work. This, unfortunately, will cause hot spots and would cause me to wipe everything off at the end of the job and start over.
My basic palette, starting at the top left corner:
Titanium White
Ultramarine Blue
Cobalt Blue
Cerulean Blue
Burnt Umber
Raw Umber (reddish tint)
Raw Umber (greenish tint)
Burnt Sienna
Yellow Ochre or Raw Sienna or both
Viridian
Permanent Green Medium (Terra Verte)
Cadmium Yellow Medium
Indian Yellow
Naples Yellow Light
Alizarin Crimson
Vermilion
Ivory Black
Prussian Blue
+ Maimeri darks
(I do not know why I originally laid them out in this arrangement but I have stayed with it)
You need a transparent and an opaque version of all the rainbow colors in order to color match because you are not just matching hues. The transparency is also critically important. Many colors can only be matched by laying down an opaque under coat and then glazing it over when dry with a transparent second color. I like the wooden palette because of the feel of the wood in my hand and the middle tone color. It is very difficult to stare at a bright white background to your colors and and then switch your gaze to your painting which is decidedly not bright white. I've been told by my photographer friends that the palette really should be a neutral "photo" gray for best color matching, but the wood works. I judge my colors while wet in the first instant of applying them to the fills and then make my adjustments immediately as necessary - too warm, too cool, too opaque, too transparent or just right. Lots of different blues are necessary because of metamerism - they are the hardest to match - but you learned about that in grad school.
Brushes:
I find the Dragon's Tongue 100% Tajmir Kolinsky from Cheap Joe's #s 1 and 2s are great. The 1's are $6.50 and the 2's are $6.80 and both hold a point very well and last a long time. A #2 with a good point is my very favorite because it holds enough paint to not dry out quickly but still is very accurate. Take care of your brushes!
Lighting:
We have a lot of northern light in the lab and this very diffuse light on a moderately cloudy day is the best. If you get the light intensity too high your pupils will close and you will not be able to do anything because you can't see much. There are many good color balanced indoor lights available now, if you need a boost. It is December in Syracuse, New York as I write this and we definitely need a boost. The Verilux natural spectrum floor lamps work very well and do not get in the way.
Tips:
Three unique colors that I could not inpaint without, especially when working with 19th C. paintings, are Raw Umber Greenish from Kremer #40630, Kessel Earth from Maimeri, and Brown Madder Alizarin from Maimeri. The greenish Raw Umber was used a lot in the 19th C and was the background base for many 19th C. American portraits. It is very difficult to match if you do not have it on your palette. This Raw Umber also has a lot of other uses when toning other colors down or making greenish gray shadows in white drapery. Kessel Earth from Maimeri is the darkest of darks I can find anywhere, it is a deeper dark black than Bone Black in PVAC(AYAB). I augment my basic powdered pigment palette with many Maimeri Colors but just for the darks - the blacks, browns, Kessel earth and Brown Madder Alizarin. They are beautifully smooth clear colors that are very easy to work with and save me a lot of time. I find the light colored Maimeri's do not have enough life in them.
I thin and wet up powdered pigments and tube Maimeris with a mixture of 47%Ethanol, 47%Isopropanol and 6% Acetone. The small amount of acetone makes the wetting of the colors go a lot faster so I can work quickly. Using an eyedropper I wet each color a little on my palette and am then ready to go. I keep two small jars of the mixture on my easel, one for dipping, and one for washing my brushes. This material is not difficult to be around and is not toxic to breath in the small quantities I am using so I am very comfortable while working and not bothered by any fumes. (Years ago I was once told by a conservator to inpaint using B72 as a binding medium for powdered pigments and xylene as the wetting agent and I tried it once - it almost killed me.)
One of the first big breakthroughs I had was when I realized by trial and error that dotting and crosshatching my colors allowed the loss to disappear much faster and with less paint than trying to work in solid colors. Also, for some strange reason I like to work from dark to light wherever possible or at least from a middle tone up. I have also learned to never try to color match with only one shot at it. I always lay down a base and then glaze. Apply a color that is close to the surrounding original paint as your first step and then cross hatch over it to do the color matching. By just trying to get close at first you end up getting a lot of work done fairly effortlessly that does not have to be removed.
Music is the best tonic for color matching and inpainting. It gets the right side of your brain working.
Another breakthrough is to learn to take your work off, even if you have hours into it. Try it sometime. If nothing seems to be working it probably isn't and never will - so go ahead and wipe it off and start over again, you will feel better and be much farther ahead in the long run. You will be surprised how the second try goes so fast and easily.
I use the Modestini varnishing technique and use it in conjunction with my inpainting. It is excellent at tying the painting together. This method uses alternating layers of brushed Ketone or other mineral spirits based varnish resins (I now use Winsor&Newton ConservArt which is an excellent and stable varnish, mostly B67 with a small amount of Ketone) with a thin spray PVAC(AYAA/AYAC) varnish. The spray will tie your inpainting into the rest of the paint layer, since it is the same resin, and then allow you to put another layer of thinned varnish on by brush without disturbing underlying layers. On some very large inpainting jobs I stop in the middle and spray the painting with B72 and let it dry for a few days to lock in all my work and then continue on with the final color matching & use the Modestini technique to finish up. My final varnish is just about always a B72 sprayed on. I matte it down when necessary with an added microwax. See spray varnishing tips here.
Colour Mixing Tips from Winsor&Newton c.1850:
Skies
Ultramarine at the top, toning down through Cobalt to a mixture of Cobalt and Vermilion near the horizon.
Difficult Greens
Greens in the shadows are actually
best made by mixing black and yellow. "For greens in shadow there is no
need of blue; they may be formed of a mixture of black and different
yellows: the olive-toned greens thus produced are soft and very
harmonious for shadows.
Should you wish the tint to partake of a light grayish cast (as in the case of willows in shadow), use Black, Naples Yellow, and White. If a yellow reddish tint be needed for these dull greens, let the yellow predominate; but if the verdant part you are painting be now so far back in the perspective that the violet gray-blue tint, peculiar to the distances, begins to take an aerial tone, then use French Blue. The greens which French Blue would give, when mixed with Naples Yellow, or with Yellow Ochre, break and are subdued by the use of Madder Lake, or sometimes by Light Red; more or less White being mixed with it, where it is required to gain an atmospheric tint.
In painting trees, it will be necessary to make the extremities of
the branches more tender in colour than their middle parts; and by
letting the light be seen through various portions, great thinness and
beauty may be attained, and thus that solidity and heaviness avoided,
which are so unpleasant to the eye."
Figure Painting-Flesh-
Rose Madder and Naples Yellow
Indian Red and Raw Sienna
Vermilion and Yellow Ochre.
Darker Shades- Brown Madder and Raw Sienna
Grays- Brown Madder and Ivory Black
Strong Shadows- Brown Madder and Raw Umber
High Lights- Pure White
White and Naples Yellow
Drapery-
White Material- White, Naples Yellow and Burnt Umber. Raw Sienna and Burnt Umber in the depths.
Black Material- Blue Black and Purple Madder. White, French Blue and Brown Madder for the high lights.
Deepest Blacks-
Ivory Black + Prussian Blue.
A
method of spraying varnish is essential in the use of the Modestini
varnishing technique and in applying final perfect finishing varnishes.
It would be impossible to apply an alcohol based varnish without the
use of a fine spray gun and it would also be impossible to get a
perfect finish on many paintings without a high quality spray unit.
Luckily these are very available today and the technology is much
improved from the old days.
I
am very happy with my modern, new HVLP gun and the new Makita air
supply system we recently purchased. After a lot of research I chose to
upgrade to an Anest Iwata LPH300LV - an HVLP gun, 3/4 size that
produces a very fine adjustable mist with little over spray, a real gem
of a find. The better autobody finisher suppliers deal with the Iwata
guns and can order you one.
A new system came out last year (2009) that allows you to use lidded detachable plastic containers that bayonet mount to your gun, so you can easily spray different varnishes without having to deal with cleaning the metal varnish container attached to the gun every time you switch varnishes. I store my varnishes made up and ready to spray in these DeKups and they make the whole system very easy to use, with little mess.
Other Useful Tips:
Acrylics can be very helpful for some paintings, murals, etc. but I find them too thick to use out of the tube. Liquitex makes a medium viscosity concentrated artist color that is very nice to inpaint with and is sold in small 59ml bottles, again from Cheap Joe's. When using acrylics I put my paint on a wet paper towel in a tin box with a lid. This keeps the colors from drying out and can even keep a palette overnight if you re-wet the towel before leaving for your evening repast at the pub.
Some days are not good for inpainting - do something else.
A lot of the problems with color matching are actually with the fill not the color. Shadows can be a real problem and cannot be eliminated by inpainting. You have to learn what you are looking at and this takes practice.
You can add small amounts of texture after inpainting in some cases by applying small dots or strokes of acrylic medium to the loss and then building a texture - it does not take much acrylic and is very effective.
Colored pencils lightly used during the last spray varnish will sometimes make that impossible spot disappear easily without having to remove or re-do your work.
Scalpels are good for careful work on proud fills - I like the larger flatter blades.
Learning to work with all kinds of different varnishes is good. Damar, correctly made and used, is still an excellent and indispensable varnish for some situations.
If you are not a professional restorer I urge you to think twice about working on a painting of your own or someone else's. If you just want to carefully paint out a small loss and do no damage use watercolor in a drybrush technique and leave the rest of the painting alone. The watercolor will do no damage and be easily removable.
Good Luck.
Links:
A Varnishing Technique Used by Mario Modestini
Mixing and Matching (Icon 2010) See article by Sarah Cove
Updated 5/06/2010
©2010 by John Sutton -