A few days ago I popped over to Sinopia’s website to see what’s new. They’ve long been highly regarded as an excellent supplier of raw pigment and paint making supplies. Among this is material for making casein paint and gesso grounds. Gesso, as you may know from some previous posts of mine, is a paint ground made traditionally with rabbit skin glue or casein, and different types of plaster solids. What was new to me is they now offer a casein based gesso that you can buy ready-made. No mixing of materials, just open the can and paint it on. I ordered a small jar of it that arrived this afternoon.
As I waited for the order to arrive, I fired off a few questions to Sinopia that they responded to quickly.
If I use this on paper, since it contains oil, should I first add sizing to the paper before applying the gesso?
“Even though the Gesso contains a linseed oil emulsion, it is completely water soluble and safe to use on paper without any sort of primer. The Casein Gesso makes a great substrate for oil painting.”
Does it have a shelf life?
“No, our Gesso does not have a shelf life. Although, once the container is opened and air gets into the jar, then the paint starts to skin over after a few weeks. In that case, the dried paint layer can simply be peeled off and the paint underneath is still in perfect shape.”
Should it only be used on firm supports? Can it be used on stretched canvas as well as wood panels?
“The Gesso works well on both panels and stretched canvas.”
Below are my first impressions of this product:
It is very thick, more so than I expected. Thicker than acrylic primers I have used, but about the same as oil primers. It can be brushed on right out of the jar, but you’ll need a good thick brush. However, it can certainly be thinned with water. If you thin it and use it as an oil paint surface, I would recommend sizing the surface first.
In the picture above I show on the left a thinned mixture (about 30% water) on a black sheet of mat board. On the right side of the board I painted 2 coats right out of the jar. I painted the 2nd coat (not thinned) after about 15 minutes, and it took about 30 minutes or so for that to dry to the touch. A hair drier can speed up the evaporation of the water content.
In this picture I’m comparing the 2 coats of gesso to Golden’s acrylic primer. The primer is much thinner, and 2 coats of it are not as bright as 2 coats of gesso. The gesso covers quite well, even on this dark black paper.
There was no information about how long to wait before I start painting on this surface. In my initial test, I waited 2 hours after applying the 2nd coat, and tested casein, oil, and gouache paint. I used the paint right out of the tube, and thinned with water or turpentine for the oil. I saw no problem with adhesion, or more importantly no reaction with the ground lifting into the paint. I even washed the surface with a brush loaded with water, dabbed it with a paper towel, and none of the white was released.
Regarding oils, it is recommended by Golden when using their acrylic primer that has been thinned with water, you should wait several days for all the water to evaporate before applying any oil paint to the primer surface. In this case, I would advise the same with the casein gesso, since there is some water already inside it.
In Sinopia’s description on the website they say this has “all the same qualities” of rabbit skin glue gesso. I would say it has some, but it doesn’t feel the same. I’ve made many gesso panels using RSG or casein (without using an oil emulsion,) and I can say that this surface feels different. Traditional gesso feels like a slab of cold stone. This reminds me more of an oil primed surface. It is a water and oil emulsion, after all. I like that feel, but it’s not like traditional gesso to me. The big difference with an oil primed surface and this, of course, is you can’t use any water media on top of an oil primer. Also, an oil primer takes a long time to cure, but this does not.
Comparing this to a traditional gesso ground, despite the different feel, this has many similarities and some benefits. RSG requires much more preparation time, and has to be held at a warm temperature while using. Once it’s made it has a shelf life of only a few days at the most. Casein gesso that I’ve made (not using emulsified oil) can last up to 4 to 6 months in refrigeration, and then starts to break down and become useless. According to Sinopia, this product can be stored indefinitely. No refrigeration is required. It’s equally as versatile as traditional gesso for use with all media, but according to Sinopia can be used on flexible surfaces like a stretched canvas, which is not true of traditional gesso.
The biggest problem I’ve had with acrylic primed surfaces is they destroy brushes. The solids in them will wear down an expensive brush in no time at all. Time will tell if this casein gesso will have the same problem. I suspect not. There are some acrylic primers that will work with watercolor or gouache, like Fredrix’s Watercolor Canvas, or Ampersand’s Aquabord, but the surface has to be made porous so they’re even rougher for brushes. Also, if you apply those primers yourself, like Golden’s Absorbent Ground, they are supposed to be applied on top of a standard acrylic ground, so you have to have both types. This casein gesso doesn’t have those problems. It appears to me at this point to be more versatile, potentially more so than any other ground on the market!
I’ve only had this for a day, so much more testing is required. My first impression is very positive.