Painting on Location
by Donald A. Jusko

Tomato Red Color Test
Colored Intonaco Mortar

All With Alum Added

1 sand, 1 marble, 2 lime, dried white.
Rough coat on 1-15-04,
dry but not hard, 2-15-04
Dry Rough Coat
1 sand, 1 lime.
Cadmium Yellow in mortar.
Quinacridone Magenta, extra center blob of yellow.

Fresco Mortar
This is a test of 3 mortars, all with alum added, 11:00. One mortar with cadmium yellow pigment added, one with quinacridone magenta and one plain. The joining lines were soft blended.
The tomato's colors are listed from top to bottom.
1, (a) Alizarin Crimson and Thalo Blue, Titanium White highlights.(b) Cadmium Red and Thalo blue, Titanium White highlights. (c) Quinacridone Magenta and Thalo Blue, Titanium White highlights.
2, (a) Cadmium Red and Thalo Blue, Titanium White highlights.  (b) Alizarin Crimson, Cadmium Yellow, Titanium White highlights.  (c) Indian Yellow br/s, Alizarin Crimson and Thalo Blue, Titanium White highlights.
3, (a) Cadmium Red, Indian Yellow Br/s, Thalo Blue, Titanium White, Indian Yellow highlights.  (b) Alizarin Crimson, Cadmium Yellow.  (c) Cadmium Red and thalo Blue, Titanium White highlights.  (d) Quinacridone Magenta, Cadmium Yellow and Thalo Blue with Titanium White highlights.
(All Chromium Green Oxide and Thalo Blue leaves.)

3 reds tomato test

Section 1, Painted with Egg and alum media, can't add second over color after first color has sunk in.
Section 2, Painted with casein medium, over paints very well.  
Section 3, Start painting 2:06, Painted with lime water media, over paints very well. End painting 3:10, still absorbing pigment. Alum added to the mortar does not effect it's absorbing time.

I put the fresco in a very hot car in the Lahaina sun for 5 hours. I had to carry the painting back hand to hand because it was so hot. There is a slight separation crack between a part of the giornate cut that was really just wet mortar against wet mortar. The mortar is now hard and sings, and I think the color change is complete. I don't think it would have cracked if it were not in that car, or if one side were dry like a normal giornate cut, or if the dry side had been painted with a cement glue additive.

Ten days later the mortar colors changed this much, the yellow and magenta lightened.
Mortar and color test

02-20-04 The last tomato was painted at 3:00, four hours after the intonico was laid. The cadmium red in the third section did not absorb. The first section is a solid fresco, painted with egg and alum, all colors were locked in. The second section, painted with casein did not absorb the cadmium red, all other colors were locked in.  I think a stronger solution of casein would have fixed that. The third section did not absorb the cadmium red and the lower right tomato did not completely absorb the quinacridone magenta. That might have been because of the forced drying and the fact that it was at the end of the painting because all the other quinacridone magentas absorbed well. I will go over the cadmium reds that need it with casein to save the fresco.
I made a buon fresco test of cadmium red, cadmium yellow, titanium white and zinc white, each color as the base for the other colors with egg, casein and lime water. Go here for the results. Another test is with Green earth.

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