What's wrong with cotton canvas?

[Thomasin Dewhurst]

What's wrong with cotton canvas, by the way? I've been ignoring the fact that most accomplished and well-collected painters use linen. But I thought I'd better ask. Is that because linen does not deteriorate as fast? I heard that linen sags more than cotton, though, and doesn't have the tautness to bear vigorous paint application.

[Richard Bingham]

Different materials for different applications and considerations.

Possibly the first consideration is material strength. The strength of yarns, and subsequently the textiles they're woven into dependends on fiber length, or the length of the "staple" as it's termed by weavers. Linen has a longer "staple" than cotton, which is the shortest of the natural fibers. Hemp has the longest staple. Synthetics (like polyester) have an infinitely long staple.

In my experience (which depends in part on observations made in the high 'n' dry mountain west, where humidity is always very low) cotton canvas stretched taut and optimally prepared will "slack off" under the attack of working a painting - vigorous brushwork, scraping, etc. Under the same conditions, linen remains stable and taut. Linen on a stretcher is more readily affected by changes in ambient humidity, however, and can slack off noticeably in very damp weather. Using linen too light in weight, too loosely woven, or too thin in thread count exacerbates the problem if lighter materials are out of scale for the size of a piece.

The long-term durability of linen depends on proper sizing and priming. It's a "nature" thing; oil of the flax seed (linseed oil) is particularly effective at rotting the stem of the plant (flax, or linen fibers). If it's not properly sized, linen canvas rots more readily than other natural fibers, but all become brittle and decay in time if allowed to absorb any vehicles and oils from priming and painting. Polyester doesn't decay in the presence of linseed oil, and can be painted on directly, without sizing or priming, if one wishes to do so.

The cachet which linen enjoys has less to do with being the best textile for painting supports, and more to do with the fact that it was the commonly used material of the "Old Masters". I've noted many patrons and gallerists will "ooh and "aaah" over linen, as if it were the gold standard, so there remains some advantages of salability for using it.

Of the natural fibers, hemp is likely the best of the three, as it is strongest, resists slacking off under a hard work-out, and seems to be least affected by changes in ambient conditions. It is, however, a bit more difficult to stretch and size.

Trivia: the word "canvas" is a corruption of the Latin word "cannabis", the name for hemp. Roman tri-remes had hemp-canvas sails.

[Michele Rushworth]

I use Claessens 13 dp linen. If I stretch it when my studio is dry (ie not on a rainy Seattle day with the windows open!), and especially if I re-stretch even tighter when the painting is done, it doesn't sag later. I love this stuff.

[Thomasin Dewhurst]

Thank-you Richard and Michele. Where does one get hemp canvas? I haven't seen it advertised in art stores anywhere. Does it come pre-primed and stretched at all?

[Richard Bingham]

Like the TV ads say, "Not sold in stores!" Hemp is not widely used (for anything) and is not widely available. Here are two links to purveyors of hemp fabrics:

http://www.pickhemp.com

http://www.hempbasics.com/store.php?crn=204

To the best of my knowledge, pre-primed hemp canvas is not offered by suppliers who sell pre-primed canvas. Of these two sources, I was unimpressed with Pickering's offerings, and there appears to be quite a marked difference in quality between textiles milled in the orient, and those made in Europe. I was quite pleased with material I purchased from the other source. There's little assurance when choosing these materials, you have to see samples, then test. Samples can be misleading, because they're all sized, fullered and pressed, which makes them appear very different when properly washed and stretched, ready to size.

Originally Posted by Michele Rushworth

. . . I stretch [Claessen's linen] when my studio is dry (ie not on a rainy Seattle day with the windows open!), and especially if I re-stretch even tighter when the painting is done, it doesn't sag later. I love this stuff.

I believe linen "behaves" very well in the environment it's prepared in. It's likely your canvases would shrink quite a bit tighter if they're sent from the northwest rain forests to a very dry climate. The good news is that a little extra tension is not really a huge problem . . . far better than slacking off and sagging!

[Thomasin Dewhurst]

Originally Posted by Richard Bingham

Hemp is not widely used (for anything)

... except it's "medicinal purposes" perhaps? ...

Thank-you for being so informative, Richard. I might try to get some and make a canvas, but I am very lazy when it comes to priming my own stuff, so it will be small. And I suppose that's a good thing if it doesn't hold up to being painted on. I might try some linen for a change too, but generally the expense always sways me towards canvas, and the comments I have received here make me think that canvas is not too bad a way to go.

Just a question or two leading on from this - I rabbit skin glued the back of one of my canvases that was a bit slack. Was that a bad idea seeing as though I didn't take the canvas off the stretchers to do it? And will this prevent proper drying of the oil paint, thus causing buckling, perhaps and problems with varnishing (if I eventually get round to doing that)?

[Richard Bingham]

Originally Posted by Thomasin Dewhurst

... except it's "medicinal purposes" perhaps? . . .

Ha ha ha ha. Thomasin, I started getting some "strange" e-mails after purchasing hemp canvas from Pickering . . . care to join the "Legalize Marijuana" movement?

Putting full-strength RSG on the back of a completed canvas is not the best idea, nor is it the best way to correct a canvas that's slacking off. On the other hand, it's not a huge error that will result in the piece self-destructing before your eyes, and the only way to do that successfully would be to apply it with the canvas attached to the chassis.

Approaches for correcting tension problems in a finished canvas, depend on how "bad" it is. A slight pucker can often be corrected by dampening the backside of the canvas with a water/alum solution. If the canvas is just a bit loose, it can be "keyed up" by tapping in the corner wedges, but this should only be done with the piece in a frame to insure that re-tensioning doesn't knock the chassis out of square. Anything these small adjustments can't correct requires pulling tacks to re-stretch properly.

Re/ RSG as a size for raw canvas, it's bad practise to saturate canvas with a full-strength glue solution, because it embrittles the canvas, and exposed glue on the backside could attract pests (like book-worms and silver fish) and a coat of glue is more hydroscopic than canvas.

The sizing is a barrier coat between the fabric and the priming, and its sole purpose is to prevent canvas woven from natural fibers from absorbing oil and vehicles from the primer and subsequent applications of paint, which will cause it to rot within a relatively short time. Nothing more. For this reason, the proper way to size a raw canvas is first to give it a "drink" of half-strength glue, which will prevent application of the full-strength coat from saturating the fabric. The full-strength glue should be applied when it is cool almost to the point of gelling, so that it will not wet the canvas to the point of saturation, and as it cools on the surface, forming a gel, should be rubbed in with the palm of the hand to even out the coating.

All this takes far more time to explain than to do!

[Thomasin Dewhurst]

Well, thank-you for explaining everything so well, Richard. This time round I really understood much better about rabbit skin gluing - i.e doing the first "drink" and the doing the second "gelling". So your time has not been wasted in this respect.

[Richard Bingham]

You're very welcome. It's my pleasure to be helpful by sharing the information I have on materials and processes.