Picture putty can be easily made with ingredients that will be readily at hand in the studio or are easily available from art suppliers. It is used to fill in areas of a painting where, while the canvas is still intact, parts of the priming or paint surface have flaked off. Should the damage be such that the canvas needs to be relined, this procedure needs to be carried out first.
The putty that is used must not be one that dries harder than the surrounding paint surface, such as would be the case with a commercial filler bought in a DIY or hardware store.
You will need the following:
Rabbit Skin Glue in liquid form
Whiting (PW18) or Blanc Fixe (PW21)
Alumina Hydrate (PW24)
Linseed Stand Oil or Dammar Varnish
Copaiba Balsam
Titanium White (PW06) or Flake White (PW04) Pigment
Other Coloured Pigment as necessary
Distilled Water
Palette Knife
Scalpel
Strainer or small sieve
Empty screw top jars
The mixing and application of the putty as described for Mixture Number 1 will generally be the same for all mixtures unless stated otherwise.
Having applied the putty, and let to dry for a short while, either impress on the repaired area a piece of canvas of the same weave as the original, in the same direction and then use a brush or palette knife to create a texture that resembles the surrounding area. If this is not done the repaired area can look to smooth and will stand out. Use the scalpel to scrape away the excess putty to arrive at the same level as the surrounding paintwork.
MIXTURE NUMBER 1
The basic ingredients of this picture putty are warm Rabbit Skin Glue (RSG), chalk - either Whiting or Blanc Fixe, an opaque white pigment - Titanium white is ideal for this, and Linseed Stand Oil. The putty can also be coloured with the addition of suitable powdered pigments, as in general the putty should be tinted as closely as possible to match the surrounding area to which the repair is carried out. To make a putty that dries to a softer consistency, replace the Stand oil with the same amount of Dammar Varnish.
Procedure:
Pour a small amount of the chalk onto the mixing surface and a smaller amount of the white pigment (a proportion of 2:1 will probably be sufficient), mix the two powders together dry using the palette knife and then make a small well in the top. Pour in a little of the warm RSG and mix together, using the palette knife, into a paste. Add a couple of drops of the Stand Oil and again thoroughly mix in. Should you so wish at this stage add a very small amount of the coloured pigment (not much will be needed to colour the mixture) and again mix thoroughly.
Application:
As a first step, Max Doerner in his well known book "The Materials of the Artist" recommends the use of Copaiba Balsam, a viscous yellowish liquid which main use is in painting restoration (it dissolves the brittle dried out skin of old oil paint and thinned with an equal amount of Turpentine restores the gloss to varnish layers), to slightly moisten the edges of the area where the putty is to be used and to help with adhesion. In practice I have found this to be unnecessary as the putty will ahere very well asit is. The only advantage would seem to be that it will make the transition between the repair and the original paint surface smoother.
A small amount of putty is then taken and rolled in the palm of the hand. This can be quite sticky but practice with use of extra whiting or other chalk as a baker uses flour in bread making. The small ball is then pressed into the area needing repair using fingers, palette knife or spatula.
It is important to remove the excess putty from the edges of the repair immediately else it will harden and prove difficult to remove easily. There will necessarily be a certain degree of shrinkage as the putty dries and one must be aware that a second or even third application may be required.
MIXTURE NUMBER 2
This will make a colourless transparent putty.
Use Alumina Hydrate, an inert pigment with no tinting power in oil. Make into a paste using Venice Turpentine (or other thickened heavy oil) and Dammar Varnish. The edges of the area being filled needs to be cleaned immediately as this mixture dries very rapidly.
MIXTURE NUMBER 3
This preparation allows for the storage of small amounts of putty in a screw top jar for future use.
In a jar fill 1/3 of it with warm, liquid RSG. Then using a strainer or sieve add little by little Calcium Carbonate or French Chalk powder until the jar is full. Close the lid and leave.
To make this a coloured putty, mix the Calcium Carbonate chalk with RSG into a paste with a palette knife, then add a small amount of coloured pigment.
Any excess of this mixture can be removed using a cotton bud dipped in distilled water.
Sources:
Max Doerner: Materials of the Artist, 2nd Edition 1976
Ralph Mayer: The Artist's Handbook of Materials and Techniques, 5th Edition, 1991
Robert Massey: Formulas for Painters, 1982
Mireia Patino & Eva Pascual: Restauration des Peintures sur Toile, French Edition, 2011
Suppliers:
1) CORNELISSENS,
105 Great Russell Street,
London
WC1B 3RY
2) KREMER PIGMENTE
Kremer Pigmente GmbH & Co. KG
Hauptstr. 41 - 47
DE 88317 AICHSTETTEN
http://www.kremer-pigmente.com/en
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