Archive for the ‘Discoveries’ Category

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Testing Gesso Made from Cellulose Gel

October 1, 2017

A few days ago I was scanning the internet looking for raw art supply materials, and I came across a site that sold a gesso mix using methyl cellulose. This was “Eco Gesso” sold by Natural Earth Paint. I was surprised, but intrigued. I’ve used methyl cellulose (MC) and Carboxymethyl cellulose (CMC) as art mediums before, but not in this manner. (Here’s a link to a previous post using MC mixed with oils.) I’ve made gesso before using rabbit skin glue (RSG) or casein for many years. My first reaction to one of this type was that MC or CMC would be too weak by comparison to serve as an effective foundation for painting; however, being naturally curious, I decided to try to make some of my own, and test it out. A $30 kit from Natural Earth sounded like too much to pay for experimenting.

I’ve read that CMC has a stronger bond than MC, so I took a teaspoon of CMC powder, and converted it into a gel by adding eight teaspoons of distilled water.

Next I added water to thin this out, and solids to make the gesso. That’s the gesso in the metal bowl.

I took a scrap panel I had, 8 x 10 inches, patched it up a bit, and applied the first thin coat.

Here’s the finished panel with 8 coats.

I had to make 3 different attempts at this. The first batch of gesso I made, using the same ratios of CMC gel that I use with either RSG or casein was too thick, and the end result on the dry panel was dusting off too much, leading me to believe the glue was too weak to hold that much gypsum. This panel is the second attempt, which had 25% less solids, but the same glue strength. It went down very smoothly, and although it didn’t powder off as badly as the first one, it still was rather weak. I could wipe the surface and get a powdery residue. I made a third attempt by using less water in the glue, and it didn’t brush on as smoothly, but still dusted off.

In summary, this gesso is much weaker than those made using RSG or casein, just as I first suspected. However, it’s not completely unusable. It’s like painting a fresco. Wet paint will turn pastel from mixing with the surface powder, but still hold. You can see the difference of this burnt umber paint on the CMC gesso panel compared to the same paint on a scrap piece of watercolor paper. If one doesn’t mind that desaturation of color, then it can work acceptably with either water based or oil based paints. The CMC powder can be found online very easily. I bought mine at a local ceramic supply store. It doesn’t have to be heated or refrigerated like the other glues, but can grow mold. A drop of preservative, like thymol, will prevent that. Personally, I’ll stick to the other glues. They make a stronger surface and are more versatile, but it’s good to know there’s an alternative.

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Casein Glue Made from Instant Milk Powder

September 23, 2017

I was at a friend’s house recently, and as we were talking about my experiments with making casein, she complained that she had some dry “instant” milk powder she had bought for her young son, but he didn’t like the taste. She let me take it home to experiment with, since I had never tried making casein from a dry powdered milk before.

This particular brand from Saco Foods is like other commercial milk powders I’ve seen at grocery stores “fortified” with vitamin A & D (and sometimes E) so I’ve always avoided using them, but there are other brands on the market that don’t have anything else added. It could be convenient and more economical to make casein from this if it works out well. It did. Here’s how I made it:

I followed the instructions to re-hydrate the powder by adding 3 3/4 cup of water (distilled) to one package, 3.2 ounces, of powder. This made about 4 cups of milk. I used a blender to mix it well, and set it in the refrigerator for 24 hours. The next morning, I poured the milk into a pot, and heated it on the stove to @150 degrees, turned off the heat, and added 1/2 cup of distilled white vinegar. Stirring for a couple minutes it congealed into a ball of casein. So far so good. I removed the ball of casein and filtered the liquid through cheesecloth to catch as much extra casein as possible, and then tore up all the casein into small pieces so it would dissolve more easily. In the picture below is a bowl of about 2.5 ounces of casein from the 4 cups of instant milk.

I rinsed the casein in clean water a couple times to remove as much of the vinegar as possible. Next I placed it in a 12 ounce jar, and I diluted 2 teaspoons of borax in 1/2 cup of distilled water that I heated in the microwave for about 20 seconds, and then added to the casein. This will turn the casein into a glue gel.

After about 6 hours or so the casein had started to transform into a gel, but was still a little lumpy. At this point I stirred in a drop of thymol to act as a preservative, and let it sit for awhile longer. After about 12 hours it had transformed into a very thick and stiff gel, about 1/2 cup.

Comparing this to other casein glue I’ve made I would say the gel from raw milk is more opaque, and gel made from dry casein powder is has a slightly darker amber tone. It does feel slightly sticky, so I would guess it will work just fine for my needs in making paint, gesso, or fixative. Very encouraging.

I’ll check out a few local grocery stores to see if I can find some instant milk powder that is unfortified. If not there are plenty of brands on the internet I could order. Here is one from Bob’s Red Mill, for example. The label says it has 0% vitamin A, so no Palm oil is added, and no vitamins D or E. The vitamin C is a natural milk component. From that 22 ounce packet I should get about 4 cups (32 ounces) of casein gel. If I remember correctly, I can get about 16 ounces of gel from a gallon of fresh milk. In powder form, the milk can be stored up to 2 years.

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Shiva Casein Paint Test Update

July 24, 2017

To follow up on my previous post, I had found that one of my Richeson/Shiva paints, Cadmium Green, transferred to a dry paper towel with just some light rubbing after the paint had dried. Now I wanted to see if other tubes I owned had this same problem. They do.

This picture shows a sheet of paper on which I painted 1 inch swatches of all the different tubes of Shiva paints I have. The paper towel at the bottom shows pigment from each swatch that transferred over. I did not dilute the paint at all with water, and did not apply the paint too thickly. All of the paints smeared easily when rubbed, some more than others, with the sole exception of the Raw Sienna. The ivory black in particular smeared very badly, and even after a day of drying felt to have a weak paint film.

Since all of the paints are old, in some cases decades old, I asked around to other people who used these paints if they could test any tubes they might have that are newer, and see if they had the same problem. I heard back from a couple people. One person had some Richeson caseins that were only months old, and found they had the exact same pigment transfer problem. The other artist rubbed the surface of paintings he had made that were at least 3 months old, and said no paint at all rubbed off. What this tells me is it might be possible that if the paint is allowed to cure for awhile longer, the pigment will adhere better and not rub off. This strikes me as a strong possibility. So, I think I’ll do a new test on paint swatches that sat undisturbed for a month or more, and then see if any pigment rubs off.

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Comparing My Casein Paint to Shiva Brand

July 22, 2017

I wanted to follow up on my previous post where I made my own casein white paint, and see how well it compares to tubes of the Shiva paint I had, and discovered something interesting. I used the paint swatch I made testing my paint on a sheet of Strathmore textured “Art Paper” 65lb.

I painted a small swatch of the Shiva titanium white, undiluted, next to the swatch of mine I had made. It may be hard to tell in this photo, but I noticed their white has a slight off-white yellowish tint to it that mine does not. I let this dry for a day, and came back and gave both a buffing with some colored fabric, and saw no transfer of pigment from either swatch. Next I placed a small piece of cellophane tape over each one, rubbed it, and removed the tape. Both transferred some paint, but more paint came off the Shiva swatch, lifting almost all the paint from the paper. The casein binder I used to make my paint was over a year old, so later I’ll see if a fresher batch performs better.

Since that tube of Shiva white is many years old, I thought I’d test a newer tube of Cadmium Green that I had to see if it performed any better. Rather surprisingly the pigment adhesion was worse. I let that paint swatch dry for about 3 hours, and rubbed the surface with a paper towel. You can see quite a bit of pigment rubbed off. The tape test pulled off quite a bit of pigment also, and the way the pigment transferred was not in sections of paint, but powdery like what I saw on the paper towel. This tells me that the adhesion on this tube of Shiva paint is poor. Granted, it’s about 5 years old or so, but it shouldn’t come off this easily. I have commercial tubes of gouache that adhere better than this. I hope the newer Richeson brand of Shiva adheres better. Now I want to test the rest of the Shiva paints I have. This is not terrible, but surprising. This paint adhesion is not much better than soft pastel.

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Plaster Coated Paper for Gouache Paint

May 4, 2017

As I get ready to prepare the surface for my new painting, I wanted to test out a ground to use especially for the grass area I’ll be painting. I’ll be using a large sheet of illustration board, and coating it with a thin ground made with spackling compound.

Spackling is a paste made out of (typically) calcium carbonate, silica, and glycol. You can find it at hardware stores, and it’s used for filling small holes and cracks in walls prior to painting. It can be thinned with water. I’ve added a small amount of acrylic medium to improve the adhesion and make it more flexible. In the picture above, I’ve drawn an area in pencil to show the rough texture it makes. It feels like a fine grit sandpaper. I applied just one coat. It creates a nice paint ground, but can lift if you use a very wet wash. Adding acrylic medium helps prevent that.

The main reason I’m using this particular ground is to allow me to lightly scrape away paint layers. You can see the marks I’ve made on the small test area of gouache paint in the picture. It will help me create a more convincing grass texture. The tools I used here are a bamboo pen and a solder scraping brush. The bamboo doesn’t dig too deeply into the plaster, and the steel brush gives a fuzzy, random scratch. I’m using various commercial gouache paint, as well as a couple of my own. This should work well for me.

UPDATE:
I’m adding a closeup of the painted area to show the scratch marks better.

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Sinopia Casein Gesso Update: Jar Problem

May 2, 2017

I’m interrupting my series of posts on the new painting to point out a problem I discovered today with a jar of Casein Gesso from Sinopia. This follows up on two posts I made in the past: one is a review of this product, and another was how I store paint containers like this upside down.

I bought this jar of gesso a little over a year ago, and keep it inside a drawer in my studio. I haven’t used it in awhile, but today I decided to open the drawer to try it out again, only to find the contents had leaked out. The lid was screwed on tight, but that wasn’t enough to stop air from getting in, and some of the contents leaking onto the drawer. Fortunately that was plastic, so it was easy to clean (that’s what that clean piece of gel is in the picture,) but I had to use a plumber’s wrench to get the lid off, and found that about 1/3 of the paint had dried out. That rounded disk inside the lid is about 1/2 inch layer of dried paint, and more dried on the sides of the jar. It had been stored upside-down.

As I mentioned in the article link above, I store containers like this upside down just for this reason. Screw-on lids of this type make very poor containers for paint, since air gets in easily. Even if this was stored upright, air gets in, and would have dried out the paint even worse. Some jars you can buy come with cushions inside the lid, sponges or thick paper, that help seal the jar. Another solution I’ve used in the past is to wrap wide tape around the outside. That has to be replaced frequently, but it’s better than throwing away paint.

Metal cans for paint make a better seal than a screw-on lid, unfortunately, a quart size can is the smallest available. Tubes are also better since the opening is smaller, so less air gets in. The best option is to use it up quickly. Prime several sheets of paper stock or canvas that you have on hand, and don’t store the left over paint for very long.

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Watercolor Paper Stretcher – Version 3

November 1, 2016

My previous version of a paper stretcher worked well enough, but it was a bit awkward and bulky in the design, so I came up with another modification.

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I replaced those 4 strips of wood clamped to the outside edge with several small strips of wood glued to the back of the frame and flush with the outside edge. Now I don’t have separate strips of wood to carry around or lose.

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In place of the screw clamps, I’m now using 2 inch binder clips attached to these strips of wood. I can fold the wet paper around the edge, and use the clips to hold it place. Now I don’t have to tape the paper to the back when it dries in order to remove the clamps. I can leave the clips on while I’m painting.

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The metal handles on the clips are also removable, which makes the frame sit better on an easel or flat on a table.

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This frame is 16 x 20.” I may build a larger one, and have the four 1/8 strips go along the whole length of the outer edge so I can place the clips wherever I want. I didn’t have enough scrap wood for that this time, but this will work just as well.