May 20, 2009
Historically, fresco was used to decorate large interior spaces – often in churches. The Sistine Chapel remains as one of humanity’s great treasures executed in this technique. In the 20th century during the great depression, the WPA sponsored many public works in fresco which yet survive today. Working in fresco is very coarse, simple and elemental. The paint is applied directly upon fresh plaster. The chemical changes that occur as plaster sets lock the pigment into the surface. There is no eraser. Small mistakes may be able to be handled in fresco secco (no guarantee). Larger mistakes simply require a fresh start.
The information here does not come from long, in depth experience, rather this is what I know from a few experiments. If you are serious and interested, I recommed a good book, course, or seminar. Notebook is an informative disinterested site with more information as well as additional links. This site from Sister Lucia Wiley a (deceased) WPA fresco artist is quite informative and helpful. If you do not have a wall handy on which to experiment, the back side of large tiles from your local tile shop may offer a highly textured surface fully appropriate for your first fresco experiments.
A wall that is ready for a mural must be of relatively even surface but coarsely textured. It must be solid and not allow moisture to enter from the rear. It is a good idea to wet the entire wall surface with a hose the night before applying the arrichio in order to insure a good bond. The arrichio is a mixture of slaked lime and sand (1 part lime putty to 2-3 parts coarse sand), applied about 1/2″ thick. It can hold the basics of the underpainting. If you are painting on tiles, you can omit this step and go straight to the intonacco.
The full scale design or drawing can be transferred to the arrichio. The Renaissance Masters seem to have used red sinopa pigment for laying in the basics of the design. It will be covered by a final layer of plaster called the intonocco, so the purpose is to lay in the complete composition to determine relationships in situ, as well as provide a guide for the ‘giornata’.
This is the final layer of plaster upon which one paints. It is a mixture of slaked lime putty, sand and powdered marble (one part lime putty to two parts fine sand plus 10% marble dust), applied approximately 1/4” thick. Be sure to wet the surface well to insure a good bond with the plaster (this is an important step in order to avoid the having plaster flake off a year or two later due to an insufficient bond). An amount of fresh plaster is mixed and plastered onto the wall (or tile) for one day’s effort (which is then called the ‘giornata’). The ‘sinopia’ (or design that has been laid on the arricio) is used as a guide to determine where to lay in the ‘giornata’. Artifical boundaries (like the traditional grid for transposition) are avoided, whereas edges of bodies, buildings etc..form natural boundaries. The working session for one day of fresh plaster can at best be 12 – 14 hours (depending on your external climate). Therefore, the design needs to be well thought out ahead of time in order to be able to complete the day’s section well and to allow it to invisibly merge with the rest of the painting. The color of the fresh paint may not exactly match that of the dried, so at least be sure that your pigment mixes are the same, then the dried painting will be fine. Allow about an hour for the fresh plaster to set before beginning to paint.
If there is no sinopia, a monochromatic design rendered full scale for the project, is then transferred to the fresh plaster intonocco via a pounce bag tapped over tiny holes that have been pricked into the drawing. This can help one to work quickly and effectively. Be careful, the pricked holes become part of the final painting, so only transfer dark lines, or use a light to medium value pigment in your pounce.
Because the action of setting the pigment occurs as a chemical change within the plaster, the pigments need to be chosen carefully. Stick with known minerals from the earth as the lime burns organic and vegetable pigments. See the seperate page for fresco pallette recommendations. Using a pallette knife, simply mix a small amount of dry pigment with distilled water to create a useable paint.
Now, finally, to painting. A tip on technique: as in watercolor, many dilute strokes can be absorpbed to build up color. In this way one can avoid large garish mistakes while gently building up the design. This of course, needs to be balanced with the need to work quickly. Remember to let an area dry before returning to it to apply fresh paint. Have on hand a variety of sizes of good sable brushes. Mix up your colors and tints before hand. Good luck. Have fun.
If you run out of time, or find small errors that need correcting, it is possible to continue in Fresco Secco after the plaster has dried.
May 19, 2009
Everything changes when you begin to do fresco. The whole process is a chemical reaction in the plaster itself that can take up to 6 months to a year to ‘cure’. So it’s really important to stick with known and trusted colors; the traditional pallette is mainly comprised of earth minerals.
Here is a list:
Raw umber – Natural earth – Highly Permanent – Tedancy to flour : needs a lot of binder
Burnt umber – Burnt natural earth – Highly Permanent – Mix it well before puddling the colour
Raw Sienna – Natural earth (Italy) – Highly Permanent
Burnt Sienna – Natural earth (Italy) – Highly Permanent – Mix it well with the brush before application
Cadmium red purple (genuine) – Cadmium sulfo seleniure – Highly Permanent
Venise red – Iron oxide – Highly Permanent – Very good light resistance – stable in mixture (Mars Red, Pozzuoli Red)
Cadmium red (genuine) – Cadmium sulfo seleniure (minéral) – Highly Permanent – Covering – don’t mix with leads or titanium white
Mars orange – Iron oxide – Durable
Yellow ochre – Natural earth – Highly Permanent – Many variations and shades of this exist, Italian, Greek, and French
Cadmium yellow (genuine) – Cadmium sulfide – Highly Permanent – Covering – don’t mix with white lead or with ultramarine blue
Viridian (genuine) – Hydraded chrome oxide – Durable – Very solid in mixture – use it in glazes
Chromium oxide green – Chrome oxide – Highly Permanent – Covering and coloring – very stable in mixture
Green earth (Terre Verde) – Natural earth – Highly Permanent
Ultramarine blue – Silico-aluminate of polysulfuretted sodiums – Highly Permanent – Luminous and intense – don’t mix with chrome yellow
Cerulean blue (substitute) – Barite sulfate and phtalocianine blue – Highly Permanent – High colouring capacity
Cerulean blue (genuine) – Cobalt stanate – Highly Permanent – Opaque – unvarying in mixture
Cobalt blue – Cobalt aluminate – Highly Permanent – Excellent light resistance – stable in mixture
Black and white
Titanium white – Titanium dioxide – Highly Permanent – Don’t mix with cadmiums – luminous – intense
Lime white – slaked lime – Highly Permanent – dull highlights, natural plaster tint
Lamp black – Carbon – Highly Permanent – the favored black for fresco
This blog space is for those who are actively working with these pigments and who want to exchange information about them. Thus additions and corrections are welcome.
May 9, 2009
It is a matter of (pretty) common knowledge that one cannot paint on a finished fresco – and hope that it will last. There are many examples of old frescos, now sadly peeling. Therefore, if you must paint secco, take my information, as word of mouth – from a professional. A professor from the Royal Academy of Art in Antwerp gave me this recipe. After five years, the secco painting still looks fine.
Pour 80 ml of methyl ethyl alcohol into a chemist’s beaker. Fill it up to 100 ml with 20 ml of Artist’s grade Shellac. Stir a bit. The size is now ready to use. Paint a coat of it over the surface of the fresco on which you wish to work. It is dry and ready for paint in one half hour.
The sealed surface is now ready for paint. Pigments mixed in water can no longer merge with the plaster for permanency, therefore, a medium is necessary. Casein, oil or egg tempera? I have read that Casein has been traditionally used, also oil, however I preferred to use egg tempera. This worked just fine.