Help, Saggin Linen!

[Richard Bingham]

Young oil paint is amazingly resilient and tough. Old paint films which have become embrittled are likely to crack and fall off the support when subjected to radical stresses.

Painting on stretched canvas is a relatively "chancey" proposition over the long haul, because the support is inherently flexible, and ultimately, the paint will not be. To avoid grief over sagging, slack, or puckering canvases, the best "fix" is for the painter to be knowledgeable on the properties of painting supports - it's hard to beat painting on your own supports if you have the skill and the time to make them.

In short, the most commonly used materials are quite given to "slacking off". Cotton canvas is not particularly strong, and will often become slack simply from the attack of being painted on. This is less of a problem for a glue-sized/oil primed canvas than for one primed with acrylic gesso which does not effectively shrink the fabric, and remains flexible.

Linen is a stronger fiber, but subject to changes in ambient humidity; slacking off in damp weather and tightening up in dry weather.

Hemp is much stronger than linen, does not get loose when worked on, as cotton does, and is much more resistant to changes in humidty, but it is not commonly offered pre-primed or pre-stretched.

Polyester is eminently stable, stronger than natural fibers, unaffected by humidity, and can be painted on directly without sizing or priming, but there is no "old world mystique" to using it.

[Mary Cupp]

I have never seen hemp canvas but it sounds quite interesting. I know the hemp fiber is exceptionally strong. Has anyone had any experience with it?

I use mostly cotton canvas but it is a compromise, as linen is so expensive. I am wondering if hemp would be an improvement without as much expense. Does anyone have any advice on using it?

[Richard Bingham]

Originally Posted by Mary Cupp

. . . hemp fiber is exceptionally strong. Has anyone had any experience with it?

Yep. Search online for hemp products. One source is "Pickering Int'l." where I bought several yards of a very good, heavy hemp twill a couple of years ago. Be advised that searching for hemp products will get you some spam from "legalize pot" groups. :wink:

Be wary of samples that look good. Before buying the twill, I purchased a medium weight square-weave canvas that looked OK in the swatch, but was heavily sized and fullered in the mill. When washed out on the frame, the intestices opened so wide the stuff resembled a screen door.

The scuttlebutt is that the Chinese use a process for preparing the raw fibers that results in shorter staples and a weaker fiber. Hemp processed in Eastern Europe is "done correctly".

Oh! Cost? As I recall, the hemp twill ran about $10 per running yard at 72" wide. I never use cotton to make up my own supports, and unprimed linen prices vary depending on weight, thread count and running width. I figure the average cost of materials for stretching and priming my own canvases runs about $2.00 per sq. ft., including stretchers and brass tacks.

I wouldn't recommend using acrylic gesso on hemp - prime with a glue size and an oil ground. Hemp can be crabby to stabilize, i.e., it's more difficult to work with and tension correctly than cotton or linen, but once the canvas is finished up, it stays put.

[Jean Kelly]

I've painted on hemp and loved it! The problem is finding one with a subtle texture instead of rough. Mine was quite textured, which was fine for the painting I was doing, but probably not good for fine detail work.

I got it from Dharma Trading Co. unsized and raw. Loved it!

Jean

[Mary Cupp]

I took a look at Dharma and found one hemp canvas product, but I was concerned that it had almost twice as many threads going one direction as the other. It also said that the shrinkage was a lot more in one direction. That doesn't sound like something that would be stable enough for painting. Does anyone have any experience here?

[Jean Kelly]

Mary,

I used the 100% hemp linen canvas, washed it first, ironed well then glued it to a pane land sized it with gesso. I still have the painting after 5 years and it has held up beautifully ever since. Washing in a mild detergent and drying it takes care of the original shrinkage, after that it is stable. This fabric and the fabrics from this company are untreated and must be cared for before painting, but it is worth the extra effort.

I'm sorry I wasn't more precise in my answer about working with hemp. I still loved it!

Jean

[Richard Bingham]

Originally Posted by Mary Cupp

. . . twice as many threads going one direction as the other. It also said that the shrinkage was a lot more in one direction. That doesn't sound like something that would be stable enough for painting.

As with most aspects of oil painting, painting on stretched canvas is a proposition that comes pre-loaded with misinformation, prejudices, mythologies, and of course, personal preferences. It is not difficult nor especially time-consuming to prepare your own painting supports in the studio, but it does require "craft" to do it well - attention to detail, some experience with materials, and common sense.

Jean has outlined the first necessary steps for dealing with any fabric stuffs for painting. Washing eliminates all "foreign" sizings and /or fullering applied in the mill and pre-shrinks the material, which will definitely make for a predictable response and a good foundation for building the support.

Glue size is called "size" for a good reason. Regardless what stresses or amount of shrinkage obtain when the material is wetted with a glue size solution, all movement is "fixed" when the glue is dry and stresses eliminated for all practical purposes. Cut an old painting off of the stretcher, and it will appear as a "slab", inert as an old piece of linoleum! Ergo, when it comes down to working with a given material, it matters not whether the warp shrinks more than the weft, so long as one follows correct procedures, and uses sizing and priming materials of optimal quality.

Working with canvases of different fibers, weights, thread counts and weave patterns I have found "square weave" materials invariably exhibit the greatest amount of shrinkage (and hence, internal stresses) as opposed to other weave patterns. Twills are nearly immoveable on the bias, with some "give" 90 degrees opposed. Some herringbone weaves can equalize stresses such that shrinkage is unnoticeable.

You would think these behaviors would make these weaves preferred supports in terms of strength and stability, but nowadays, one seldom encounters other than square-weave linen and cotton in varying weights and thread counts, although hemp and other weave patterns were common enough in earlier times .

In terms of long-term durability, panels are a better support than stretched canvases, but problems with surface quality, flatness and the weight of large panels have made stretched canvas the "best solution" for many hundreds of years. In any case, 80 to 100 years is about the lifespan of a stretched canvas before re-lining becomes necessary.

However, canvas glued to a panel isn't going "anywhere", not being subject to the same stresses as a stretched canvas, or the possibility of being punctured, dented, torn, or becoming slack on the stretcher frame, and sagging, bagging, or puckering.

[Thomasin Dewhurst]

Richard, What's the best glue to use for gluing canvas onto board? And for what reasons?

And what happens to foamcore / gatorboard after time (with the foam centre) - if it deteriorates, how do you get the canvas off to re-glue it to something else?

Thanks!