As conservators caring for a range of paintings in the QAGOMA collection, we began to notice that some contemporary paintings on pre-primed canvases do not always behave predictably during conservation treatments. This, combined with questions from artists, led us to a three year collaborative project with colleagues in Singapore and Melbourne to assess the range of commercially primed canvases currently available to artists.
The aim of this project was not to recommend one brand over the other, but to enhance understanding of current products and consider potential influences that the canvas and priming type may have on conservation care.
Historically, fabric supports for easel paintings have been made from linen or cotton fibres and primed using glue or oil-based layers. More recently synthetic fibres have become available for canvases, and synthetic polymer primers are now commonly used as preparatory layers. Many commercially pre-primed canvases are marketed with a ‘universal primer’ – intended to be suitable for both water and oil-based paints. Canvases commercially primed with oil-based primer are also available to artists.
We began our project by asking 28 Australian painters about the canvases they choose. Most responded that they always purchase pre-primed canvases either off the roll or pre-stretched, with only one painter choosing to apply their own priming. Canvas selection was guided by trial and error, availability and working qualities, with price point being the fourth consideration. Most artists did not vary their canvas choice when working in different mediums (i.e. oil or acrylic paint). Interestingly, slightly more artists were working in oil paint than acrylic.
We then sourced 53 commercially primed artist canvases from Australian and Singaporean suppliers, documented and analysed the canvases using various scientific methods — characterising the fibre that makes up the fabric, the canvas weave and also the type of coating used as the commercial priming layer. The scientific methods and results we used to study the canvas samples are summarised in ‘Investigating commercially-primed artist canvases: supplementary data’ and discussed in a paper that is to be published in 2021 (Carter et al, submitted).
In summary, fibre analysis showed good correlation with the information provided by manufacturers — with most canvases being cotton, followed by linen. Polyester (polyethylene terephthalate — PET) was found in only a few samples, including as a cotton/PET blend. Three weave patterns were identified in the canvas fabric — most were plain weave (1 x 1 thread), followed half basket (1 x 2 threads) and a few as full basket (2 x 2 threads). Cotton was typically found as half basket, while linen, PET and PET/cotton blends were mostly plain weave. These weave patterns reflect manufacturer design to strengthen weaker fibres by doubling the thread (full basket) or by doubling only the warp or weft (half basket). Typically we found that half basket cotton canvases with their uneven weave pattern showed the most uneven response to moisture.
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Universally primed canvases were found to have ‘synthetic polymer’ priming layers. A range of synthetic polymer types were identified, including acrylic, polyvinyl acetate (PVAc) and acrylic/PVAc copolymers with and without styrene. The high incidence of styrene was a surprise as in the past it has been associated with cheaper materials and poor stability. Generally acrylic copolymers are considered to be more stable than PVAc, although there are many factors influencing long term ageing.
34 different synthetic copolymer combinations were found in the 53 samples — with no two primed canvases showing identical formulation (except some of the same brand — but not always). This wide variety of synthetic polymer binders used in commercial priming layers suggests the artist canvas industry lacks specific standards and makes it very difficult for artists to know exactly what copolymer is used in the canvas they are purchasing. Consistency is not guaranteed even within brands nor between batches and we found it difficult to purchase the same product twice, even using the same product code.
Pigments and fillers identified in the samples were predominantly titanium white and chalk in the synthetic priming layers, most often in combination but sometimes singly. Other pigments and fillers including barium sulfate with titanium white and/or zinc white were found in fewer samples, primarily in oil priming layers.
Within the small number of oil-primed canvases analysed, ‘zinc soap’ formation was evident in some canvases — potentially posing a risk to subsequent oil-paint adhesion. Often the oil primed canvases were found to also contain synthetic polymer based underlayers, so the benefits of choosing an oil primed canvas are unclear.
One of the main recommendations from this research is for painters to avoid leaving commercial priming layers exposed as a white colour in their paintings. This is because many of the universal priming layers contain styrenated acrylics which can become yellow over time when exposed to ultraviolet light from daylight or some light fittings. Priming exposed as part of your painting may be vulnerable to yellowing if it contains styrene, thus it is recommended that priming should be covered with paint.
Anne Carter and Gillian Osmond (QAGOMA) with Lynn Chua and Filzah Mohd Amir (Heritage Conservation Centre, National Heritage Board, Singapore) and Ruby Awburn (Independent Conservator, Australia)
Aspects of this research have been presented at two symposiums during the 3 year project, and the posters from those conferences are also included below.
- Anne Carter, Lynn Chua, Filzah Mohd Amir, Ruby Awburn, Gillian Osmond and Joey Ng. ‘Investigating commercially-primed artist canvases’ in eds. Ian McClure, Cynthia Schwartz and Jim Coddington Conserving Canvas, Getty, (submitted).
- Anne Carter, Lynn Chua, Filzah Mohd Amir, Ruby Awburn, Gillian Osmond and Joey Ng. ‘Investigating commercially-primed artist canvases: supplementary data’ QAGOMA website, 2020.
- Anne Carter, Lynn Chua, Filzah Mohd Amir, Ruby Awburn, Gillian Osmond and Joey Ng. ‘Investigating contemporary pre-primed artist canvases’. Poster presented at Conserving Canvas Symposium, Yale University, October 2019.
- Gillian Osmond, Lynn Chua, Anne Carter, Ruby Awburn and Filzah Mohd Amir. ‘An FTIR survey of contemporary pre-primed artist canvases’. Poster presented at the 13th Infrared and Raman Users Group symposium, Sydney, December 2018.
- Joey Ng and Yeow Liang (Heritage Conservation Centre, National Heritage Board, Singapore) are gratefully acknowledged for the cross section images.
- QAGOMA Foundation
Featured image: Commercially primed canvas for sale on a roll by the metre / Photograph: Anne Carter / Courtesy: Art Shed Brisbane