Table of Contents

Stucco Priming

Name: Nina Elizondo-Garza

Date and Time: 

2019.March 1, 12:30pm

Location: Chandler 260 (Making and Knowing lab)

Subject: Introduction and methodology

The focus of this work was to examine the efficacy of glue as a ‘primer’ for painting stucco and whether it would affect color intensity, texture, and durability once the stucco was painted. During this first session in the lab I made new batches of rye flour, chalk, and plaster of paris-based stucco following the same recipe and measurements as in my previous research from 2017 [link].

Due to time constraints in Fall 2017 I was not been able to recreate the author-practitioner’s recipe for stucco which is made over a 30 day period. Over the past year however Naomi had spent 30 days making the recipe (her process can be found here [link]) and as such the powder was ready to use in the lab. The author-practitioner instructs the following in f. 29r:

“If you want that the work stays white, it is better to mold with plaster instead of flour. It is true that it is more brittle and firm as well, but one needs to prepare it like this: temper it, when it is powdered strong, in a good amount of water so that it is clear, & grind it several times a day for fifteen days. Then pour off the water by tilting, and gather the plaster & grind it finely on the marble, & place it in some kind of clean lead vessel, so that no dust & dirt falls into it, & leave it in the open air & au serain for fifteen days with its water, and it will become matte, strong, white and light, very suitable for making a groundlayer for burnished gold. And this, in powder form, you can mix, instead of flour, with tragacanth gum, and your work will be very beautiful.”^[1]

As described by Naomi in her notes, she made two batches: one which was mixed over 15 days as per the instructions, and one that was not mixed, to determine whether the mixing had any effect.

My methodology would be as follows:

1. Make rye flour, chalk, and plaster of paris stucco, as per Fall 2017. Also, make new batches of stucco using Naomi’s mixed and unmixed stuccos and follow the measurements from my previous research and the author-practitioner’s instructions.
2. Make 4 discs of each variety, stamped with the flower cookie stamp I used in Fall 2017 to show the stucco’s ability to be molded and take impressions.
3. Of each type of stucco, paint one disk in rabbit skin glue, fish glue, and paste glue. One disk of each type would remain un-glued as a ‘control.’

To simplify this explanation, I present this table demonstrating how this would be laid out once it was done:

4) Each disk would be painted. I decided that, to get the most out of this investigation, I would use the same pigment for all of them to attempt to standardize results. Each disk would be conceptually divided into fourths: one fourth would be left unpainted to show what the stucco looked like either bare or with the glue on it, one fourth would be painted using tempera (egg yolk), one fourth would be painted with glair (egg white), and one third would be painted using oil-based paint (using linseed oil).

The goal of this research was twofold: first, to determine whether priming the stucco with glue made any difference to its appearance and its ability to hold pigment. This was inspired by the author-practitioner writing that:

“Next, you will apply [the stucco ornaments] with strong glue or paste glue, as you like, and you will be able to paint and decorate them with gold & all colors.”

It is unclear in the manuscript whether he means that the stucco ornaments can be applied to a surface using strong glue or paste glue, or whether he means that they can be ‘primed’ to then be painted and decorated. I use the word ‘prime’ as a verb to mean that a surface has been coated with a preparatory layer before painting which will increase the paint’s durability and its adhesion to the surface, but it should be noted that the author-practitioner does not use this word in this entry. In Fall 2017 we experimented with using glue to affix the stucco to a surface, so that part of the work has already been completed [link here].

The second goal of this research is to determine whether his 30 day stucco recipe results in good, appealing, durable, whiter stucco, as he claims it will.

Name: Nina Elizondo-Garza

Date and Time: 

2019.March 8, 11:30am

Location: Chandler 260 (Making and Knowing Lab)

Subject: Making the new type of stucco

I worked in the fume hood because inhaling the stucco powder was a hazard. I mixed up a large batch of tragacanth gum to ensure I had enough to work with and wasn’t going to run out half way through.

Both samples of Naomi’s stucco powders began as 150g of plaster in water as per Naomi’s detailed spreadsheet. For consistency (both in terms of  texture and in terms of the experimental process), both stucco bases were ground down. Both samples were housed in similarly sized jars, but the ‘unmixed’ stucco took up less space in the jar.

The ‘mixed’ stucco plaster in a jar it looked like flakes or tablets of plaster [see slide 59 in Naomi Rosencranz’s presentation]. Grinding these into a powder was difficult as they formed pellets when crushed. The mixture needed to be both crushed and sieved before use. As it was mixed into the tragacanth gum, the resulting substance was surprisingly stretchy and squishy. It felt like raw pizza dough. This serves to highlight a passage in the manuscript where the author practitioner says that the stucco mixed with tragacanth gum should feel like bread dough when it’s ready to be used. None of the other types of stucco had this texture, so it was interesting to have more clarity into the author-practitioner’s descriptive language. Unfortunately I did not have enough stucco powder to fully reach bread dough texture, and the mixture was very sticky. It was difficult to fully incorporate the mixture into the gum. Also, in order to take impressions of this very wet ‘dough’ I had to place the small ‘dough’ ball onto an oiled glass dish to be able to peel it off once it had been stamped. I used linseed oil for this. Given more of this plaster and more time, I believe it could have been incorporated better, and it would have ultimately felt like bread dough, which could lead to smoother results once the stucco is dry.

Image of set-up in the fume hood to make Naomi’s stuccos, including the pot of hydrated tragacanth gum and the oiled glass plate described above:

Image: Sieving the ‘mixed’ stucco powder, resulting in small pellets which needed to be crushed:

Image: demonstrating the unprecedented stretchiness of the Naomi’s ‘mixed’ stucco combined with tragacanth gum:

The ‘unmixed’ stucco was deceptively easy to work with in that it absorbed the tragacanth and incorporated into it very well, and there was almost no residue on the glass slab when kneading it. However, there was not enough of this stucco powder for it to reach a consistency where it could take an impression. I had used up all the powder in the jar and it was still extremely wet and did not take impressions at all. More stucco powder is required to fully examine the difference between stuccos, but, superficially, we can tell that unmixed and mixed stuccos behave very differently when combined with tragacanth gum. I was able to make enough stucco base out of the mixed powder to create several imprints to use for the gluing/painting stage of the experiment. I was not able to get enough stucco base from the unmixed powder. Because I was not able to get any stucco impressions from the unmixed powder I would only glue and paint four different types of stucco, not five, like I initially indicated in the first entry.

Name: Nina Elizondo-Garza

Date and Time: 

2019.March.18, 2:00pm

Location: Chandler 260

Subject: Making glue and paint, then painting the stucco disks

 Previous M&K researchers have theorized about what “strong glue” is -- see Casa Wang, “Making and Using Fish Glue in Ms. Fr. 260” from Spring 2017 and Dr. Maartje Stols-Witlox, “Grounds, animal glue, and starch” from June 2016 for specific information-- and so I decided to use an animal glue and a fish glue, since either could be considered “strong glue,” and paste glue made from wheat paste. For animal glue I used rabbit skin as the base as this was readily available in the lab. For the paste glue, we were operating under the assumption that the author-practitioner’s “paste glue” was similar to the paste glue we were familiar with, i.e. sieved flour and warm water, as described by Cennini.^[2]

I used Kremer’s fish glue (product code 63550), diluting it slightly with warm water so it could be applied more smoothly with a paintbrush. Once applied it had a slightly yellowish tint, and it was very shiny. I only put one coat on.

I used rabbit skin glue ‘pellets’ that were already in the lab, using a 1:10 ratio between the glue and water. These were melted in a bain marie kept between 40-60 degrees celsius. Once applied, it was less shiny than the fish glue, but it did not have the yellowish tint. Like the fish glue, I only put one coat on.

I used a 1:1 ratio of wheat flour and water for the paste glue, though I sieved the mixture after it had boiled and coagulated for a more even texture, again so that it would coat the stucco disks more smoothly. While the rabbit skin and fish glues applied evenly and well to the stucco when applied with a paintbrush, the wheat paste glue absorbed into the disks, meaning I had to put more than one coat on-- this was particularly noticeable in the chalk stucco which had crackling on its surface.

Image: demonstrating the un-sieved lumps in paste glue:

After being sieved the paste glue was much smoother and had a texture similar to the hydrated tragacanth gum.

Image: all the disks with glue applied, drying before being organized. This photo also includes one disk that was not painted, bearing the pattern of a pine tree and stars. This was made using Naomi’s ‘mixed’ stucco using a wooden mold, since the original stucco research tested the difference between using wooden and metal molds on the author-practitioners stucco recipes. Please see the original annotation/field notes for those results. In this case, the wooden mold impressed on the stucco almost as well as the metal mold.

Image: the stucco disks which would be painted, organized according to their type and which glue was used (if any).

These needed to dry before I could paint them.

Name: Nina Elizondo-Garza

Date and Time: 

2019.April 17, 10:30am

Location: Chandler 260

Subject: Painting stucco

Image: disks and painting set-up. Please don’t be alarmed by the superficial disorganization, each disk had been labelled on the back.

The glues had mostly dried, however, the fish and paste glues were a little sticky. I thought it was negligible and continued with my plan to paint.

I separated the egg yolks and whites and frothed up the egg white to get a smoother and more regular consistency from it when I mixed it with pigment.

To reduce the amount of deviation in the final product I chose to use the same pigment for each type of paint. I used Venetian Red, an earth pigment, because I knew it could produce a vivid color. Further experimentation should attempt this using a mineral or natural pigment, to see how stucco (whether primed or unprimed) takes the color well.

I am including this diagram to show how each stucco disk was separated into different quadrants. Each stucco disk was placed on the tray facing the same angle, meaning that this key should apply to all of them when viewed in the photograph:

The segments on the flower petal stamp led to an easier time dividing the disks. One petal segment was left ‘unpainted’ to show what the stucco looked like underneath.

I used one layer of paint on each disk, mixing pipette-measured individual batches of each on a glass slab as I brushed on each type of paint. The fish glue and paste glue became even stickier when they came into contact with the paint, which made painting them a bit challenging to get even coverage. The stucco disks were so small that it didn’t make a difference but I imagine that if we had a larger glue-coated stucco project it would be an inconvenience. Also, the glair did not absorb as well as the other paints, it seemed to rest on the surface. The oil did not take well to the non-glued stucco, meaning I had to use comparatively more paint to get even coverage.

In case the post-it notes on the image are difficult to read, here is a chart rendition of the pictured layout:

There are a few noticeable variations according to the stucco base, the glue used, and the paint type.

The rye stucco disks took the paint well and resulted in vivid colors all around, with slightly lighter toned reds when using tempera paint and a uniform texture using the oil paint.

The Naomi ‘mixed’ stucco does indeed have a very white appearance, and they were also the thinnest of the disks without sacrificing detail from the stamp. They did not take glair well at all, as it looks blotchy. Even the oil paint garnered mixed results. The tempera paint uniformly produced the best results, across all the different glue types.

The chalk disks have always had the most cracking on the surface, but priming them with glue resulted in an even texture. They took the glair well, but the tempera and oil paints continued to produce the most uniform and vivid results.

The plaster of paris disks had the most varied results, as the rabbit glue served to highlight all of the cracks on the surface rather than hide them. Both the rabbit and the paste glue did not take the glair well at all as the results were also quite blotchy. The other glue and pigment types however took quite well and produced vivid and smooth results.

Overall, it seems that stucco choice, glue choice, and paint bases do have a visible difference in the end result when painting stucco. While fish glue generally resulted in appealing colors and textures, the disks which received no glue priming before being painted also look good --for the most part-- suggesting that the author-practitioner meant that the stucco should be glued onto other surfaces with strong or paste glue, rather than be primed by glue.  

A further check on the disks at the lab should be carried out to see whether the colors have changed over time.