Acrylic Gesso vs Oil Primer: Understanding Cold-Weather Failure Risk
Research by Christina Young and Eric Hagan sheds critical light on how modern primers perform under cold conditions. Their 2008 study, “Cold Temperature Effects of Modern Paints Used for Priming Flexible Supports,” focuses on mechanical failures that can occur in both acrylic gesso and oil-based primers when exposed to cold conditions. The study compares the performance of acrylic gesso vs oil primers at cold temperatures. These findings offer crucial insights for artists working with flexible supports, particularly those who incorporate historical painting techniques into contemporary contexts.
The Hidden Vulnerability of Priming Layers
Most artists consider the ground layer simply as a preparation for painting. However, this layer has a structural role that becomes especially important under environmental stress. When temperatures drop to roughly 25 °C below a primer’s glass transition temperature (Tg), the layer shifts from ductile to brittle and can no longer absorb handling stresses. Minor actions—such as unrolling a painting, tightening a canvas, or transiting vibration—may then initiate fractures that remain invisible until they propagate through the paint film.
The authors found that primers can shift from ductile to brittle behavior when temperatures drop to roughly 25 °C below a primer’s glass transition temperature (Tg). When this happens, even minor handling stresses—such as flexing from unrolling a painting, tightening a canvas on a stretcher, or shocks encountered during transit—can result in fractures. These brittle failures may originate below the paint layer, making them difficult to detect until more extensive damage occurs.
This is particularly concerning for paintings that travel between locations or are stored in conditions where environmental control may be inconsistent. Understanding the mechanical thresholds of priming layers helps mitigate these risks through better material selection and handling procedures.
What Is Glass Transition Temperature?
The glass transition temperature helps artists predict how a paint’s flexibility changes in response to temperature variations, influencing its mechanical performance. It marks the point where the material changes from a flexible, rubbery state to a rigid, glass-like state. Below this threshold, paint films are far more prone to cracking.
An analogy may help: imagine a rubber band placed in the freezer. As it cools, it loses flexibility and may snap instead of stretching. Similarly, paint films that fall below their Tg become more brittle and fracture under stress that they would typically withstand when warmer.
Hi George,
I’m confused, sorry. You say, “Note how oil grounds perform better,” but the only oil ground is WN Foundation White, and it has a Tg of 40, the second highest number on the chart. Yet the article states, “Lower Tg values generally correspond to greater flexibility at low temperatures, which reduces the risk of brittle failure.” That seems like a contradiction. I must be missing something, or I’m reading things wrong. How does your Lead Alkyd primer fare in light of the abysmal alkyd flexibility? That’s one of the two primers I use (Gamblin’s Oil Ground being the other). I thought acrylic was worse in winter because the oil and lead grounds remained more flexible in cold temperatures. Now, I’m wondering if I should paint outdoors with unprimed surfaces. Does Gamblin’s PVS size crack in colder temperatures as well? Thanks for your help. I enjoy your articles and videos,
Bill
Bill, I will answer your questions in several replies because they deserve a more in-depth discussion:
Why does Foundation White (Tg ≈ 40 °C) still outperform the alkyds?
Tg is only one factor. Young & Hagan reported that the W&N Foundation White (a lead-white oil ground in drying oil) fractured at lower strains than acrylics at room temperature, but unlike the alkyd primers, it did not become catastrophically brittle at 10 °C.
Why? Drying oil films (linseed) continue to polymerize and remain slightly ductile than the alkyd resin network, even though the lead-oil ground’s Tg is high. In contrast, the alkyd binders cross-link quickly, and their networks stiffen early, so once they pass below Tg, they crack with almost no plastic deformation.
A high Tg does not guarantee poorer low-temperature performance if the binder chemistry still allows limited plastic flow. That said, Foundation White did crack at 0 °C and –10 °C—just a little later than the alkyds.
How might a lead-alkyd primer fare?
The study did not test a primer that combined lead carbonate with an alkyd binder. Evidence suggests:
Binder dominates cold-weather behavior. An alkyd network—even pigmented with lead white—will likely behave more like the other alkyd primers (brittle by 10 °C) than like the pure drying-oil ground.
Lead pigment may slightly modify the Tg or modulus, but it will not override the alkyd resin’s rapid stiffness increase below Tg.
If you rely on that primer in cold temperatures on flexible supports, avoid rolling or aggressive stretching once temperatures drop to near freezing.
Is acrylic worse than oil or lead grounds in winter?
Acrylic gesso can remain flexible to ~10 °C, but several commercial brands in the study fractured at 0 °C or –10 °C.
Lead-oil ground lasted a bit longer but still cracked in sub-zero tests.
The bottom line is that below freezing, all modern grounds tested became brittle—none are immune. Acrylic is not automatically “worse,” but product-to-product variation is large.
Should I paint outdoors on un-primed surfaces?
Painting on supports without a primer avoids primer brittleness but introduces other problems (absorbency, staining, and long-term oil embrittlement in the textile). A more practical tactic is to:
• Paint on rigid supports, such as aluminum composite materials (ACM) panels, which are less susceptible to changes in temperature than flexible supports such as stretched canvas.
• Keep supports above 5–10 °C until the painting session starts.
• Apply low-Tg acrylic or oil grounds known to tolerate moderate cold.
Thanks, George! Excellent feedback, as always. I noticed recently that your lead oil ground dries within a few days. I purchased the Alkyd version to avoid the long dry times (6 months or more) of regular lead grounds. It looks like I can skip the Alkyd version for now on and avoid the extra brittleness.
Does Gamblin’s PVA (polyvinyl-acetate) size crack when cold?
Pure PVA films generally keep good flexibility well below 0 °C (Tg often < 0 °C), so the size itself is unlikely to fracture. However, if the ground on top becomes brittle, differential movement can still cause cleavage at the size/ground interface. Keeping the whole package above freezing remains the best practice.
Hi, George,
This article left me wondering:
What is the Tg of Rublev Lead Oil Ground?
What is the Tg of Michael Harding’s Non-absorbent Acrylic Primer? Would this value be in any of the manufacturer’s spec sheets?
Would the Tg of clear primer differ from the same primer in white or another color? Probably, right? But in which direction?
I’m amazed the Tg values are all room temp or higher. Really???
Thank you!
Gabrielle Savage Dockterman
Michael Harding markets Non-absorbent Acrylic Primer (NAAP) as an “acrylic styrene copolymer” with heavy mineral and carbon-calcium fillers. The company does not list Tg on its datasheet, and third-party test data are not publicly available.
Most high-solids styrene/acrylic gessoes fall between 25 °C and 35 °C. Because NAAP is formulated to be harder and less absorbent than typical acrylic gesso, the Tg is probably at—or slightly above—the top of that range.
How to verify:
Ask Michael Harding for a DMA or DSC value (they sometimes provide internal test numbers on request), or send a cured free-film to an independent lab for DMA.
A clear acrylic “primer”—without TiO₂ or CaCO₃—usually has a Tg a few degrees lower than its white counterpart, meaning slightly better flexibility in cold weather. However, studies by GOlden Artist OClors show that oil paint is likely to crack on clear acrylic primers.
Modern primers are engineered to provide a hard, sandable, toothy surface in normal indoor conditions. Manufacturers aim for Tg ≈ 25–45 °C so the dry film is firm yet coalesced without co-solvents. Unfortunately, that places the ductile-to-brittle transition close to ambient temperatures in unheated studios or transport trucks. Older animal-glue/chalk gessoes or low-Tg acrylic dispersions (Tg < 15 °C) remain flexible further below freezing but have other drawbacks (swelling, poor solvent resistance).
Rublev’s Lead Oil Ground differs from Winsor & Newton’s Foundation White in two important ways:
Rublev uses bodied (heat-polymerized) linseed oil, whereas Foundation White relies primarily on raw linseed oil. Bodied oil already contains longer, partially cross-linked molecular chains, so the film starts off slightly stiffer and shows a higher initial glass-transition temperature (Tg).
Rublev’s formula contains a higher proportion of basic lead carbonate relative to oil, producing a dense, highly filled film. Heavy pigment loading further restricts polymer-chain mobility, nudging Tg upward.
Given these factors, a fully cured free film of Rublev Lead Oil Ground will likely exhibit a Tg in the 30–40 °C range—3-5 °C lower than the ~40 °C measured for W&N Foundation White. Over the first year of curing, bodied oil films continue to oxidize and can gain another few degrees in Tg.
Bodied oil still retains more ductility below Tg than an alkyd network. Consequently, Rublev Lead Oil Ground should behave somewhat better than alkyd primers and slightly better than Foundation White when temperatures approach freezing. Keeping supports above 5–10 °C during handling remains the safest practice.