Splined Canvas | A New Method of Stretching Presents Challenges for Structural Conservation
Over a few months during the fall of 2021, five paintings came to the Williamstown Art Conservation Center with a support that the paintings lab was unfamiliar with: a splined canvas strainer (fig.1). Two contemporary artists active in New England were represented in this group, both of whom had been using commercially prepared, splined strainers purchased between 2004 and 2020. Despite being readily available in artist supply shops or Amazon, discussions, written records or other valuable information about this type of stretcher does not seem present in the field of painting conservation.
The paintings came to the WACC for evaluation of condition concerns such as mold from flood damage and tears. Addressing these issues unveiled some of the challenges that conservators may face when handling this type of support. Aspects of their condition necessitated the release of the canvases from their splined stretchers as part of treatment. During this process, it was discovered that the construction of the splined strainer prohibits an easy release of the canvas. Furthermore, reusing the spline to re-stretch the canvas may result in damage to the tacking margins. This article will present the history of stretching canvas, highlighting the method of construction used for splined stretchers. Risks and concerns will be given for treatment of these supports with an example of how to overcome the challenge of re-stretching canvas onto a splined strainer.
FIGURE 1. Example of a splined canvas strainer.
The way that a canvas is adhered to its auxiliary support can provide a wealth of information about a painting. The method of stretching the canvas and the tools and materials used to attach it to its support can tell us about the support’s manufacturing history, the artist’s technique, and previous conservation treatments if any. Today, the most common supports for canvas paintings are stretchers and strainers. Strainers have fixed joins (fig.1). In contrast, stretchers have expandable joins that may be adjusted to improve tension without removing the canvas (fig.2).
FIGURE 2. Example of a traditional five-membered stretcher. Stretchers have 1-2 keys in each expandable join.
FIGURE 3. Example of securing the canvas along the tacking margin with tacks.
Typically, a canvas painting is folded over the side of the auxiliary support and secured on the tacking margins or fold-over edge. Throughout history, the materials and methods used to attach the canvas to its stretcher or strainer have evolved from lacing, wooden pegs, glue, tacks, and nails to more modern staples and splines. Beyond the advancement in fasteners, canvas paintings have also seen a change in the location and placement of the attachment along its auxiliary support. A common sixteenth-century practice was to nail the canvas support directly to the face of the auxiliary support before painting, having no excess canvas along the edges [1]. Similarly, South American and Spanish Colonial paintings in the seventeenth through nineteenth centuries also lacked a canvas selvage, and the canvas support was glued directly to the face of the stretcher. In the seventeenth through eighteenth centuries there was a shift towards stretching the canvas support around the sides of the stretcher and securing the canvas to its stretcher with nails and tacks along the tacking margin (fig.3). This is the most common type of attachment we see in the lab. During the 20th century, this tacking margin was generally left unpainted and, in some cases, unprimed [3].
In the 19th century, there was a shift from traditional artist-prepared materials to an industry of mass-produced commercial products. This included commercially available stretchers, strainers and pre-primed canvases. While pre-primed canvases were commercially prepared and sold by English colormen as early as 1677, the move to strained canvases or pre-stretched canvases became more popular starting in the mid to early 19th century [4]. It was not until the late 19th and early 20th century, with the development of more uniform stretcher bars and the invention of canvas pliers, that artists could purchase stretcher bars and pre-primed canvas to make their own stretched canvases.
A more modern variation is the gallery wrapped style. “Gallery wrap” is a method of stretching a canvas in which the canvas is wrapped around the sides of a stretcher or strainer and attached to the reverse of the wooden support (figs.4-5.). Typically, gallery wrapped canvases are manufactured with a commercially primed canvas. This creates a clean appearance, free of visible fasteners, such as staples or tacks, and allows the margins to be a part of the artist’s composition (fig.3, fig.5). This style is popular among artists who prefer to display their work unframed.
FIGURE 4. Reverse of a gallery wrapped stretcher without keys placed.
FIGURE 5. Edges of a gallery wrapped stretcher.
Gallery wrapped canvases can be split into two categories: back-stapled and splined. Back-stapled canvases are fixed to the back of the stretcher bars and the canvas itself has uncut corners and generous selvage (fig.4) [5]. Comparatively, the splined canvas (sometimes referred to as a tuck and roll style) is secured to the back of a strainer with a rubber spline tucked into a slat or channel cut into the reverse of the stretcher bar (fig.6a-6b).
FIGURE 6a. Reverse of a gallery wrapped splined strainer. The joins of the strainer have been fixed with staples to prevent expansion.
FIGURE 6b. Detail of the splined strainer. Excess selvedge is secured by the white rubber spline tucked into the strainer bar channel.
The first mention of the production of splined canvas supports was in Mexico as early as 1996 at the Tara Materials manufacturing facility [6]. A US patent for the idea of a splined canvas was applied for by Kathryn H. Dix in 2000. The patent was approved May 28, 2002, under the name “Minimal Contact Stretcher.” Dix claimed, “there is a need for a stretcher bar framing structure that can have material attached to it without the need for staples or other fastening means” [7]. The solution was a stretcher frame that “contains a channel so that the canvas material is folded over the top along an exterior surface and folded into a channel so that a rubber spline may be inserted attaching the canvas to the frame without the need for staples.” [8]. The popularity of splined canvas stretchers rose dramatically amongst American artists and students in the early 2000s [9]. Artists desired the clean and “professional” look that the splined stretching method provided.
Currently, almost all of the splined canvas stretchers sold in the U.S. are made abroad in China, Mexico and Vietnam, as noted in the U.S. International Trade Commission investigation on Artist Canvas’ from China. The variety of manufacturers results in some differences amongst the brands; however, the overall components are the same. The auxiliary support, in this case the stretcher or strainer frame, is composed of four kiln-dried wooden members. Some larger stretchers have cross bars or corner braces for additional support. Each member is beveled to reduce the contact between the wood and canvas surface. Depending on the manufacturer, some stretcher bars have steeper beveled angles than others, while some have a raised beading along the outer turnover edge of the stretcher bar instead. Some brands are manufactured as strainers, as the corners are joined at a mitered joint and secured with two staples in the corners. Other manufacturers join the corners using a mortise and double mitered joints. This version is theoretically expandable; however, typically the wood members are stapled in the corners for extra support, effectively making it a strainer. The element that these variations have in common is the channel that runs parallel to the outer edge on the back side of the four main strainer bars (fig.6b). It is this feature that makes the splined canvas strainer unique. The pre-primed cotton canvas is hand stretched onto the strainer members using a blunt chisel to push the edges of the canvas into the channel. Afterwards, a mallet is used to hammer the rubber spline into the groove in the wood to fix the canvas in place. The corners of the canvas are stapled on the reverse and several staples are fixed in the groove to secure the rubber spline in place. The corners are cut and trimmed out rather than folded so the canvas lays flat along the reverse. The excess canvas that is not tucked into the channel is then cut for a clean appearance.
Beyond the aesthetic benefits of a clean finish or deep edge, the most apparent advantage to splined canvas stretching is the limited number of puncture holes created in the canvas. We see an array of damage to tacking margins caused from rusty tacks or staples that corrode the canvas fibers around them. This is the only benefit that we can ascertain from our evaluation of this type of support. The disadvantages caused as a result of a painting stretched using a splined stretcher, far outweighs the aesthetic benefits. The most obvious disadvantage of the splined stretcher is the difficulty in removing the canvas from its support and re-stretching it. The fixed nature of a splined canvas does not allow for the tension to be adjusted, so the canvas is more likely to sag over time [10], requiring re-stretching or the reduction of planar deformations. Re-stretching and other structural treatments, require the conservator to temporarily release a canvas from its support. Similarly, an artist may need to release a painting from a splined stretcher in order to roll it for storage or travel. The challenge then in either case, is how to safely restretch the canvas using its original stretcher. While researching splined stretchers, several videos were found highlighting the idea that these canvases are difficult to re-stretch using the spline and groove method. Some suggested the canvas cannot be removed from the stretcher at all, and must be cut off its stretcher. Others suggest using sharp instruments to chisel away the wooden frame to have better access to the spline. All of these examples demonstrate the difficulty presented in the structural conservation of contemporary paintings on splined strainers. Ultimately, the conservator must spend quite some time using a fine spatula and pliers to carefully remove the rubber spline and gently coax the edges of the canvas out of the channel (figs.7-11).
Re-stretching the canvas to its original support presents its own unique challenges. This mostly stems from the manufacturers trimming the corners and excess selvage canvas, limiting the amount of usable canvas to adjust tension while stretching (fig. 12). A sufficient amount of excess canvas is needed to re-stretch the painting in an even manner without risking damage to the tacking margins. Another component that can lead to potential conservation issues are the rubber splines themselves. As rubber ages, it weakens and can become more fragile and brittle, making it more susceptible to breaking when being handled, removed, or adjusted. The rubber spline wraps around the entirety of the stretcher, making it impossible to just release one side or area along the margins. Instead, the entire spline must be removed.
Because the margins are often painted and intended by the artist to be part of the composition, careful considerations must be taken to protect the margins and preserve the alignment of the canvas on the stretcher. Paintings done on this type of stretched canvas are typically left unframed, leaving them more susceptible to damage.
FIGURE 12. Excess selvedge is scant or short in a manufactured spline strainer. These short tacking margins are difficult to re-stretch with appropriate tension.
The conservators at the WACC who needed to re-stretch the five paintings onto their original splined strainers experimented with two methods. Two attempts were made for each method, using the original rubber spline in both cases. The first attempt was made by adding toned Reemay®, adhered with BEVA film, to reinforce and extend the scant tacking margins. A standard phillips head screwdriver was found to be the best tool to retuck the canvas into the channel in the stretcher bar. While the Reemay® is inherently thin, the excess material made it more difficult to push down into the channel. The second attempt was made without the addition of Reemay®, however this made it much more difficult to pull the canvas to the proper tension.
The most successful re-stretching technique was to add Reemay® secured with BEVA film to the scant margins (toned to match the image) and match the previous folds and stretching. The canvas was adhered to the reverse of the strainer with staples through the Reemay®. Similarly, a grosgrain ribbon can act as a barrier between the margin and the staple as the canvas is re-attached to the stretcher bar.
Splined Gallery Wrapped strainers are widely manufactured and in frequent use by contemporary artists due to their clean aesthetic. This type of support presents challenges for removal and re-stretching of canvas and, therefore, many aspects of structural conservation. It is important to both document this type of support and share the findings with contemporary artists and our colleagues in the field of art conservation. Ultimately, the WACC conservators recommend attaching a strip lining and abandoning use of the channels and rubber spline for re-stretching. This methodology can help prevent damage to the tacking margins while providing the conservator with the adequate tension needed to properly re-stretch a canvas.
Photography Credit
Photography by Maggie Barkovic.
[1] Stoner, Joyce Hill and Rebecca Anne Rushfield. Conservation of Easel Paintings. 1st ed. Routledge 2021. pp. 153-159.
[2] Ibid, p.154.
[3] Katlan Alexander W. American Artists' Materials Vol. Ii : A Guide to Stretchers Panels Millboards and Stencil Marks. Sound View Press 1992. pp. 20-29.
[4] Ibid.
[5] BLICK art materials, Materials for Artists (USA: Dick Blick Company, 2020), p.190.
[6] Artists’ Canvas From China, Inv. No. 731-TA-1091, USITC Pub. 3853 (May 2006).
[7] Kathryn H. Dix, Minimum Contact Frame, US Patent 6393742B1, filed 2 March 2020 and issued May 28 2002.
[8] Ibid.
[9] Artists’ Canvas From China, Inv. No. 731-TA-1091, USITC Pub. 3853 (May 2006).
[10] Elsayed Ahmed Elnashar. Compact Force Effects of Canvas Stretched Woven Fabrics and the Angle-view on the Philosophy of Painting "Ages" of Artist's Sergi Cadenas. American Journal of Art and Design. Vol. 5, No. 1, 2020, pp. 1-11. doi: 10.11648/j.ajad.20200501.