Notes from The Painter’s Handbook 2: Sizes and grounds

(This is the second in a series of blog posts sharing my notes on the fundamentals of building a durable oil painting, based on information in the book, The Painter’s Handbook by Mark David Gottsegen. Please understand that I am not the expert here; I’m putting these notes out there for me just as much as I am for you, the reader. Start with part one, Notes from The Painter’s Handbook 1: Oil painting supports.)

sizesgrounds

So, after selecting a painting support – which in my case, will continue to be something solid like hardboard – the next thing to figure out is how that support is to be made suitable for accepting oil paint.

Sizes for Oil Paintings

  • In this context, “size” has nothing to do with the dimensions of a painting. It is a thin glue or resinous mixture that is applied to a raw support. It should sink into the support’s surface without coating it.
  • Fabric (canvas, pre-primed or otherwise) supports first need to be mounted on something: either stretched on bars or adhered to an auxiliary solid support.
  • Pre-primed canvas, once mounted or stretched, needs no additional preparation.
  • “Raw” (unprimed) canvas and panels need further preparation with a ‘size’ followed by a ‘ground’ before accepting oil paint
  • Sizes must be correctly prepared and applied or damage to the painting will result
  • One traditional size is hide glue (sometimes referred to as rabbit skin glue). It can be used as a size on fabric, paper or to mount fabric to a panel.
  • Hide glue has a serious drawback: it is extremely “hygroscopic” meaning it “tends to absorb and expel atmospheric moisture, even when apparently dry – and its response to changes in temperature and relative humidity can be extreme. It shrinks greatly when humidity is low, and expands considerably when the humidity is high. Both responses put undue stress on a relatively rigid and brittle dried oil paint layer, especially when it has been painted on a primed or unprimed flexible support and stretched…The oil paint has little choice but to crack under these conditions…hide glue is generally denigrated as a size and is not recommended for a textile that is to be primed and painted with oil-based paints.” (p. 52) Because it’s an organic substance, hide glue has been known to attract hungry insects and molds as well.
  • In other words, sizing raw linen with rabbit skin glue helps to accelerate the eventual destruction of the painting. Yet, for reasons that are a complete mystery to me, many, many artists still insist on doing this. As far as I can tell, it’s mostly because of tradition: doing things the “Old Masters’ way” despite considerable 21st century scientific knowledge that shows alternate materials and methods to be far superior.
  • Other sizes include gelatin, starch, methyl cellulose (all organic and hygroscopic), and acrylic resins which do not react to atmospheric humidity. All of these options are considered “reversible”; they can be redissolved and removed at a later date, if necessary.
  • Acrylic resins (varnishes) that can be used as size: Golden Artist Colors’ MSA/UVLS or Liquitex Soluvar
  • Irreversible sizes include acrylic dispersions (aka polymerized acrylic resins or “matte medium”), and polyvinyl acetate dispersions (aka PVA or common white glue). Gamblin Artists Colors makes a PVA size. Golden makes an acrylic dispersion medium called GAC 100 that can be used as a size.

Grounds for Oil Paintings

  • Ground is sometimes referred to as “primer” and is applied to the support after it has been sized
  • Provides tooth for the paint to grab onto
  • Makes future conservation efforts easier
  • Should be white – not tinted – in order to maintain color relationships and brightness in the oil colors which become more transparent with age
  • Should be somewhat absorbent
  • Should cover evenly and not leave open pinholes in fabric supports
  • Should be immune to most of the movement (expansion/contraction) inherent in flexible (stretched fabric) supports

Oil Grounds

  • An oil ground is the traditional one for oil paintings, made from lead white pigment + linseed oil. Lead white must be used with proper precautions as it is toxic. Winsor & Newton makes a lead white that can be used as an underpainting or ground, called Foundation White.
  • Other white pigments that can be used: titanium, zinc and combinations of the two, but these are less durable when linseed oil is the vehicle. Poppyseed, safflower or other non-yellowing oils are better choices; read the label to see what’s been used.
  • Note that zinc is sometimes combined with titanium to make the white whiter, but the resulting paint film is more brittle than titanium alone.
  • White alkyd resin grounds are considered to be an improvement over traditional oil grounds; manufacturers include Winsor & Newton, Gamblin, and Daniel Smith.
  • Two coats of oil ground are recommended for priming

Acrylic Dispersion Grounds

  • The correct term for an acrylic ground is “acrylic dispersion ground” rather than “gesso”. I tend to refer to this stuff by the shorthand term of “acrylic gesso” because I am well aware that it is not the same thing as traditional gesso (which was made from chalk, pigment and hide glue). The two products have very different ingredients and surface characteristics. So be aware that acrylic dispersions – even if labeled “gesso” by the manufacturer – are NOT the same as traditional chalk-based gesso.
  • Beware of cheap “no name” acrylic dispersion grounds. Always use the good quality name brand stuff. And never use latex house paint.
  • Because acrylic grounds are about 50% water, you should use at least four coats to prime your support.
  • The water content in acrylic grounds can take up to 30 days to evaporate completely, even if it feels dry to the touch within hours. This water content can dissolve organic materials in the panel or fabric resulting in something called “Support Induced Discoloration” or SID. To avoid this, a product like Golden’s GAC 100 or GAC 700 is recommended as a size to isolate the support from the ground. I must interject here that I personally have never noticed SID on the panels I’ve primed and I have used acrylic gesso (Liquitex) for years. Sometimes I use the primed panel fairly quickly, but others have sat around for years with no noticeable discoloration whatsoever. So this SID problem is news to me. Still, keep it in mind.
  • Acrylic dispersion grounds are “…brilliant white, very adhesive, and retain flexibility and toughness as they age”. (p. 60)
  • Can be used on most permanent supports (flexible or rigid) that are not oily or greasy
  • Do not apply over hide glue without an intermediate layer of a GAC 100 or 700 product
  • Application and cleanup are easy as these grounds are water-based. I use a paint roller and keep it wrapped in plastic in the freezer so I never have to wash it.
  • Acrylic dispersion grounds are questionable to use under oil paints on flexible supports (i.e., stretched canvas) because acrylic  remains flexibile and oil paint becomes brittle with age. This can be avoided by adhering the fabric support to a panel or mounting on a panel stretcher.
  • Recommendation is that paintings on a flexible support of 3 square feet in area (or larger) use an oil ground.
  • Never try to reuse old oil paintings by re-priming with acrylic ground. This violates the “fat over lean” rule
  • When used on rigid supports, acrylic grounds can have somewhat less tooth for the paint to key into.

Traditional Gesso Ground

  • An ideal ground for a rigid support is the traditional gesso made of chalk, pigment and hide glue. However, this ground is brittle, so should not be used on flexible supports.
  • A gesso + oil emulsion ground (aka “half-chalk” ground) is sometimes used on rigid supports. It is more flexible but will yellow with age.

That’s it for now. There’s a lot to digest here. In addition to longevity, your choices may be influenced by your particular working habits and preferences. It’s a bit of a balancing act – what’s the point of using, say, an oil ground if you hate how it feels under your brush?

Up next: Solvents.


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