Isolation Coats Between Acrylic Paint Layers

Note: This page may be frequently updated.

Inspired by the Old Masters’ or Maxfield Parrish’s methods of painting in layers of transparent glazes over an underpainting (verdaccio or grisaille), one can elect to use acrylic mediums as isolation coats between each layer or every few layers of colored acrylic glazes.

The basic process is do the underpainting, let dry, lay down an thin layer of acrylic medium (not varnish) as and isolation coat, let dry, do a thin layer of glaze color or three, let dry, lay down a thin layer of acrylic medium as isolation coat, let dry, repeat with layers of colored glaze and isocation coats as you see fit. Before you finally add varnish, if you even varnish your painting, you’ll add one final layer of acrylic medium as isolation coat, and let dry. That’s the basic process.

A layer of isolation coat before varnishing your painting will protect your painting during any future restoration efforts.

Painting in layers method fascinates me, and I’d like to try it with acrylic paints, so here’s some of what I’ve gathered so far. Isolation coats, if done right, allow for maximum play of light between the layers of color.

A simplified presentation of glazing in acrylics is shown at Soft Gel Gloss (an acrylic medium) is ideal for both glazing layers and isolation coats. Gloss is best because it allows for optimal passage of light. Thin it with water in a 2:1 Soft Gel Gloss to water ratio or use straight (stronger in paint removal situations).

The Basic Method

  • Do a colored background. The initial colored background sets a color mood and helps to unify the painting. This is just a colored background and it comes before the underpainting.
  • Let it dry. (Golden Open Acrylics may not dry completely overnight, by the way. Also, if you want them to dry faster, lay down very thin paint layers, thinner than a dime. Golden warns that their open acrylics may not be suitable for the underpainting layers and suggests their High Flow acrylics for underpaintings in one of their videos.)
  • Isolate. Lay down three thin diluted or undiluted layers of Soft Gel Gloss acrylic medium on top of the background color, letting each layer dry individually.
  • Transfer sketch.
  • Do underpainting.
  • Isolate. Lay down an isolation coat or three, your preference.
  • Let dry.
  • Add transparent colored glaze layer(s). Thin the artist grade acrylic paint colors with acrylic glazing liquid/fluid rather than water. See warning about thick layers of the acrylic glazing medium. In other words, keep your layers using acrylic glazing medium thin and let each layer dry sufficiently. Also, a 1:10 paint to acyrlic glazing medium is a recommended ratio.
  • Generally. Here’s a page on Golden Paints acrylic glazing medium.
  • Dry each. Let each transparent colored glazy layer dry before doing the next.
  • Etc. Add as many alternating transparent colored glaze layers and protective isolation layers as desired…
  • Drying Time — Let the painting cure a few days to a few weeks, depending on how thick and numerous your paint layers are.
  • Final isolation coat. Use Soft Gel Gloss acrylic medium 2 parts Soft Gel Gloss to one part distilled water. Practice first and note about avoiding bubbles.
  • Final Piece Drying Time Before Varnish is Applied The two stages of drying for acrylic paint are when it’s dry to the touch and when it’s cured. Dry to the touch may or may not equal cured. It’s cured when the complete thickness of acrylic paint and mediums are completely dry all the way though. The cured stage determines the ultimate physical properties —  adhesion, hardness and clarity — to fully develop. For very thin films, cure time may be a few days, while films of 1/4 inch thickness or more will take months and even years to be completely dry.
  • Varnish layer. Varnish for acrylic paintings.

That is not the only method of painting but it’s the one I’m focused on now.

Matte vs. Satin and Gloss Acrylic Mediums for Isolation Coats

Some say they use some matte medium, for texture, over the glossier isolation coat between layers. That would add a opacifying haze if matte medium were chosen for the clear layer between each colored glaze layer. Choose matte medium once or twice, especially in background or in initial layers, and then it’s probably okay. Matte medium opacifies somewhat and lightens colors. It would interfere with the play of light between layers if you rely on it too much yet it can be advantageous in limited situations.  I tried matte medium over a dark starry night sky background surrounding a luminous figure and it turned out fine.

Maxfield Parrish, Color Layers

Painters like Maxfield Parrish would have abraded the clear isolation layer with very fine loose pumice before adding the next layer of colored glaze. Light travels through all the transparent layers (glazes), bounces off the canvas, travels back up through the layers of glazes and reflects back at you.

In this way, you get both optical mixes of colors and a luminosity that you can’t achieve with a physically mixed color. Additional layers of clear coats between the layers of colored glazes might help with that play of light and can prevent previous layers from being disturbed as the next layer is worked.

As I try underpainting, then adding layers of colored glaze in acrylics, I’ll have to experiment regarding matte medium vs. fine loose pumice abrasion vs. just adding the next layer of colored glaze after each isolation coat.

Strength and Removability

Golden Paints reports that, as far as their line goes, there is no significant difference between the soft gel and most other gel mediums in regards to strength. I’m going to try using Golden Polymer Medium as an isolation layer too.

The MSA and the Polymer Varnish are removable with mineral spirits and ammonia, respectively.

Acrylic Soft Gel is generally not removable (unless you use strong solvents and physical abrasion that might degrade the painting surface more than what’s desirable).

Benefit of Painting in Layers Like This: Correction and Removing Fresh Layers of Colored Glaze Acrylic Soft Gel

Any glossy surface, Golden Paints says, allows thin layers of fresh paint to be added and they can be removed with rubbing alcohol. It would be difficult to remove a layer of cured undiluted gel medium with alcohol but a thinned out acrylic paint or medium (with water ) is a weaker film, and can be easier to remove, especially if fresh and painted on a less porous surface (like a previous layer of cured acrylic medium used as an isolation layer).

To clarify, an artist may not remove the Acrylic Soft Gel medium, but may sometimes remove thin layers of freshly applied paint with alcohol. Carefully.

Golden Open Acrylics for UnderPaintings

I have some Open Acrylics I want to use as underpaintings. I think I’ll use them in the thinnest of layers, perhaps drybrushing them on, and then I’ll let them dry a couple of weeks before proceeding with the layers of polymer medium(s) and transparent colored glazes (for which I’m going to use Golden Fluid Acrylics and Da Vinci Fluid Acrylics). Since the underpainting contains the composition and values of the painting, I think it’ll be worth the wait.

Bonus Notes: Verdaccio Colors!

Note that verdaccio was traditionally made from what we’d now call Mars Black, Yellow Ochre, White (use Titanium, not Zinc White), and a very small amount of light red (was cinabrese)

So what to use for red in acrylic verdaccio mixes in our times? A tiny touch of Cadmium Orange + Quinacridone Rose? A touch of Perinone Orange + Cadmium Red Medium? You may want to try the artist grade fluid acrylics for the Quin Rose? I like that. Napthtol Red? Vermilion Hue can be found in the form of Winsor & Newton Galeria acrylic. Permanence A series 1. The pigment is Napthtol Red (PR9).  Unfortunately, Galeria are student/studio paints of flowing consistency with a relatively low pigmentation so the coverage will be poor. Almost all vermilions that you can get in the United States, whether oil or acrylic, are convenience mixtures and are not true Vermilions. Golden Paints offers its Historic Acrylic colors, in which they have tried to recreate the look, feel, and characteristics of some pigments that were either too toxic to use with waterbased acrylic binders, or that are no longer available. Alizarin Crimson Historic Hue is the only red but it’s not a cinnabar or china red. Try mixing cad orange [ PO20] and quin magenta [PR122] in fluid acrylics with cadmium red in heavy body acrylics (perhaps open acrylics)? An azo red is a mid shade red, probably with more rose than orangish undertones? Azo condensation red is sometimes also known as transparent vermilion. Golden Acrylics says: “Vermilion (PR 106) is a toxic pigment made from Mercuric Sulfide. This naturally occurring ore is the source for Mercury, and was ground up as a pigment for centuries and termed Cinnibar or Zinnober.

Early cultures of the Greeks, Romans and Chinese created Cinnabar artificially for centuries, as early as 6th century B.C., but it wasn’t until the 15th century that it was termed Vermilion. Direct sunlight causes it to darken substantially, and it was quickly replaced by the Cadmium Reds upon their arrival. …

Toxicity may also cause a pigment to fall into disfavor. Pigments made from lead or mercury, such as Naples Yellow or Vermilion, can be poisonous and may have inadvertently killed many early artists. It is believed that Vincent Van Gogh’s mental illness and suicide may have been due, in part, to his frequent use of true Naples Yellow. Many of these very toxic pigments were replaced by the Cadmium family of pigments, which in turn are yielding to better choices in the evolution of pigment selection. Although Cadmium is less toxic than lead and mercury, it is still a heavy metal with an uncertain future due to continued regulatory concern.

“As part of GOLDEN Artist Colors’ ongoing efforts to provide safe products, we have introduced several organic colors as replacements to the Cadmiums — Pyrrole Red, Pyrrole Red Light, Pyrrole Orange, and Hansa Yellow Opaque.” Try Quinacridone Red in Golden’s Heavy Body Acrylics.

Reference Resources: “In addition to being similar in hue and chroma, these colors have greater exterior durability than cadmium pigments.”

How about fluid acrylics? Rose Madder Quinacridone Da Vinci Fluid Acrylic is a more permanent and stronger color. It’s readily replaced by quinacridone rose (PV19) or quinacridone magenta (PR122 or PR202). You can modulate it with a thin glaze or addition of pyrrole orange (PO73) to simulate the effect of the purpurin dye, if you like. I like the Rose Madder Quinacridone Da Vinci Fluid Acrylic option, personally. Because I have that already, I tried it, and it worked well.

Bonus Video Values and Verdaccio underpaintings:

5 thoughts on “Isolation Coats Between Acrylic Paint Layers

  1. Pingback: My Fourth Painting: “Shimmer,” 24″x24″ | KarenAScofield

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