MITRA Forum Question Details

​Hi

We cover this in the following thread:

https://www.artcons.udel.edu/mitra/forums/question?QID=164

All the best,

Sorry. I believed that was covered as well and inserted it without rereading. What attaching to the back achieves is that it is both more aesthetically pleasing if the work is to remained unframed but also it allows for ample fabric to retensioned if the work ever needs to be removed from the stretcher. As a conservator who regularly has to restretch paintings, I can tell you that is very difficult to do so when there is only fabric on the tacking margin. Probably the best method (if one is not trying to achieve a “clean” edge) would be to allow for a wide tacking edge, tack along the sides, and staple the extra fabric to the back to allow for future conservation work. When stapling please follow the 45 degree angle as mentioned in the above thread.

The following Conservation Wiki speaks to this issue:

https://www.conservation-wiki.com/wiki/Stretchers_and_Strainers:_Factors_to_Consider#Variations_Due_to_Application_of_Stress.2FStress_Concentrations_of_System

The results appear to be more complicated than a simple superiority of one method over another. Tacks appear to have contribute less stress but attaching the canvas to the back is also less stressful to the surface of the painting. Here is the salient text:

In a comparison of the relative merits of staples vs. tacks, they found less concentration of stress with tacks. Tearing was also a problem with staples, particularly if the staples were not absolutely parallel to the edge. If they were not perpendicular to the direction of the load, stress would be concentrated in one of the staple “legs” and tearing was much more likely. Similarly, up to a certain load, the staple would act as a “bridge,” meaning the load would be distributed along the entire length of the staple. However, above a certain load, slippage of the fabric under the staple's middle would occur, and stress would be concentrated at the two legs, which would often result in tearing. The sharp rectilinear edges of the staples certainly play a role in this; therefore rounded “wire” staples are preferable. Tearing was not a problem with tacks. Historically, failure of the fabric around the tack was the result of deterioration caused by the rusting of the tack, a problem easily eliminated with the non-ferrous tacks available today. Closer spacing of either staples or tacks led to reduced stress/strain concentration. Staples applied diagonally to the tacking edge showed no difference in stress distribution to staples applied parallel to the edge. Staggering the staples added stress concentrations, however, probably due to the greater amount of fabric in front of some staples.

In comparing attaching the fabric on the face, on the side, and along the back edge, the further the attachments were from the picture plane, the more even the distribution of stress. There are probably two factors at work here: more fabric to even out the stress and the friction of the stretcher bar. In general, the authors calculated the side and rear attachment resulted in 67% and 45% of the stress of front attachment, respectively. The application of card between staple and fabric was also studied. A continuous piece of card, running the length of the edge, was most effective at distributing stress more evenly, and thicker card was more effective than thin card or fabric tape. Probably the stiff card works like the “bridge” of the staple, distributing the stress over a larger area and mechanically resisting cusping. All the canvasses attached using staples showed visible cusping, and the authors found secondary cusping could be formed by restretching as little as four weeks after priming. Preliminary indications show that care must be taken in restretching to minimize the potential of creating secondary cusping. Further research on this topic is currently being carried out by the authors (Young and Hibberd 2000, 212–220).