Introduction

The main idea of our project was to experiment with and study how different binders can be used in paints. From an artist's perspective, the idea was to find out how well certain binders caused the paint to go on to the paper, how well they adhered to the surface of the paper, the general look of the paint, and how easy the paint was to use and to clean up. We made the paper that was used ourselves, and tested three different binders-egg tempera, linseed oil, and gum arabic-with three pigments-Cadmium Red, Cadmium Yellow, and Ultramarine Blue-to create different paints to brush onto the paper.

Background

Egg tempera was first used as a binder by the early Egyptians, and was a main choice of painters up until the Renaissance, when it was replaced by oils. A famous example of egg tempera is Botticelli's The Birth of Venus. It was not widely used again until the 19^th century (www.eggtempera.com).

Watercolors also did not become popular until the late 19^th century. Before this time, it was primarily used only as a wash with other mediums.

Procedure

The first step was to make paper to paint on. We initially chose to use cotton pulp, 400 mL for each sheet, and made 11 sheets. It was then brought to our attention that sizing is needed to strengthen and waterproof the paper. Sizing is used to fill the pores of the paper, the gaps between the fibers, so that the paper does not overly absorb water. We attempted two different types of external sizing on our already dry paper, including spray starch and a homemade potato starch, neither of which was succesful. We began the entire process over, this time using hard wood pulp that already contained drops of internal sizing, and made 12 sheets. When the sheets dried, they buckled and waved instead of drying flat, so we ironed them and then tested them using droplets of water to make sure that they were somewhat waterproof, and were this time successful. Once the paper was ready, it was time for the paints. For the three binders, we chose egg tempera, linseed oil, and gum arabic. The three pigments we used were Cadmium Red, Cadmium Yellow, and Ultramarine Blue.

The first binder we worked with was the egg tempera. Egg tempera required that the pigments already be in a paste form, so we added water to each of the dry pigments and ground them on the glass with the muller. We placed the ground pigment into baby food jars until the egg yolk could be added.

(insert picture mullergrindWEB.jpg)

To prepare the egg tempera, the egg must be cracked and the yolk separated from the white. The yolk is the only part of the egg necessary to create the paint. The yolk can be separated by pouring the egg back and forth between the egg halves, allowing the white to run down the sides. Once the yolk is separated, the yolk sac must be punctured and the yolk itself drained out; the yolk sac is not included in the binder. We discovered that the yolk sac is very delicate and often punctures itself with no help from the artist. The yolk is then added directly to the pigment and stirred, at about a 1:1 mixture. Once the yellow color of the yolk is gone, the paint is sufficiently mixed and can be applied to the paper using a wide brush; we applied three brushstrokes of each color to lessen the possibility of abnormalities.

To test the strength of the binder to hold the pigment together-the spreadability-we used a dropper to make three drops of each color on a sheet of paper. The more the paint spreads, the weaker the binder can be considered to be.

The second binder we worked with was the oil. The oil is applied directly to the dry pigment and then ground on the glass. The method we used was to make a pile of dry pigment on the glass, create a crater in the middle, and then drop 20-30 drops of linseed oil into the hole. Rather than use the muller for such small amounts of pigment, we found that the back of a teaspoon worked just as well with some applied pressure. The oil made a very pasty paint, but dried out so quickly we were unable to transfer it into baby food jars, so we dipped the brush directly from the glass and applied the paint to the paper. The paint was very difficult to load onto the brush due to the fact that the paint had a very thick and quick-drying consistency.

(insert picture annaoilsWEB.jpg)

The paint went onto the paper very thick, so we attempted to thin it out using mineral spirits. We added several drops of the spirits to disperse the oil and lessen the thickness , then mixed the paint until it was smooth and applied the paints to another sheet of paper.

The oil paint was too thin and pasty to even be gathered up by a dropper, so we were unable to test the spreadability by making droplets.

The third and final binder we used was the gum arabic to make watercolors. The watercolors were made using the same method as the oil. The gum arabic was applied directly to the dry pigments along with distilled water and ground on the glass using the back of the spoon. We gathered the paint directly from the glass onto the brush and made three strokes of each color on the paper.

(insert picture spoongrindWEB.jpg)

We were able to test the spreadability of the watercolors by using the dropper to make three droplets of each color on a separate sheet of paper.

Once all the paints had been applied to the paper and dried, we measured the La*b* coordinates with the colorimeter.

Observations and Data

The egg tempera was fairly effective as a binder. The colors turned out very vivid with a shiny texture on the paper. The paint covered the paper fairly well with one brushstroke, although some paper did still show through. After the paint dried, there was no flaking or cracking. The droplets created using the dropper created round beads on the paper and dried that way, with no spreadage at all.

The oil paints were not as effective. The colors were very deep and rich, rather than being bright like the egg tempera paints. The oil paints also did not cover the paper very well at all. The oil that had been thinned with mineral spirits covered the paper better, but not particularly well. The paint seemed almost dry on the paper, and came off in a powder when touched. We were unable to test the oils using the dropper due to the consistency of the paint.

(insert picture twooilsWEB.jpg)

The watercolors were the most effective. The paint stayed very wet while on the glass, making it very easy to work with, but dried within minutes of application. The colors were flat, not shiny like the egg tempera, but were very bright and vivid. There was no cracking or flaking, and the paint did not come off at the touch; it adhered to the paper very well. The coverage was excellent; the paint went on in one stroke and no paper showed through. The drops created using the dropper did not stay beaded on the surface like the egg tempera. They slowly spread, forming small pancakes of paint on the surface.

Data gathered from the colorimeter:

Conclusions

The oil paints were the least effective as a binder. They were difficult to work with because the dried very quickly on the glass plate, barely allowing enough time to apply them to the paper. As mentioned in the observations above, the paint itself did not stick to the paper, but came off on anything it touched. The oils were also difficult to clean up. Water is not effective, due to the fact that oil is hydrophobic. Mineral spirits must be used to clean all brushes and utensils, including the glass used for grinding. The clean up process was very time consuming.

The egg tempera was a much friendlier binder than the oil. Not only did it go on thepaper better and have better coverage, the clean up process was much easier. Water worked well to clean the utensils. The only difficulty was in separating the yolk from the white without breaking the yolk sac before it was time. The paints also do not last very long, and a new egg must be used everyday to create more paint.

The watercolors were by far the most effective binder on the paper, as well as being user friendly. The paints covered the paper almost entirely, with no paper showing through. Creating the paint was extremely easy, since the gum arabic mixed well with the dry pigment and stayed wet long enough for us to work with it. The clean up process was wonderful, since water washed away any paint or pigment within seconds.

Links

www.eggtempera.com

www.chasrowe.com

www.kamapigment.com

www.angelfire.com/yt/modot/

Acknowledgements

Dr. John Bordley

Printing Materials: A Short Encyclopedia, by Rutherford J. Gettens and George L. Stout, 1966,

The Artist's Handbook of Materials and Techniques, by Ralph Mayer, 1982.

Travis Johnson & Anna Williams