Help, Saggin Linen!

[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!

[Julie Deane]

Thomasin, I'm sure Richard will give you excellent advice, and if you wish to research your question further, check out www.amien.org.

I recently have glued up to 36 x 48 inches on Dibond panels successfully. Also smaller wood panels. I've used either PVA glue or Liquitex gloss medium. With the wood, one needs to add a protective coat to it before gluing.

[Richard Bingham]

Originally Posted by Julie Deane

. . . I recently have glued up to 36 x 48 inches on Dibond panels successfully. Also smaller wood panels. I've used either PVA glue or Liquitex gloss medium. With the wood, one needs to add a protective coat to it before gluing.

Julie, thanks for the vote of confidence. What I recommend is to "do what works", and test to make sure your methods are sound. If I contradict a suggestion, or make one of my own that doesn't "set well" with some readers, the test is the final arbiter.

Gluing raw canvas to a wooden panel, I would use rabbit-skin glue. Hide glues "draw". The easiest way is to temporarily tack the canvas to the edges of a wooden panel (that includes plywood) and saturate the canvas with glue. Some shrinkage is desirable, and the "draw" as the glue sets makes for a flawless interface. I would NOT apply a coat of any kind to raw wood, it's been my experience that a film of anything, shellac, varnish, "sealer", etc. interferes with the glue bond. If it were desirable to apply coatings to glue joints, you can be sure luthiers would do so when building instruments; they do not.

Di-bond and alumalite are faced with aluminum sheet, which makes a glue which becomes brittle (such as PVA) a questionable choice. Currently, conservators are not averse to gluing canvas to such supports with "Beva-Gel" which is also a modern option to traditional maroflage. It's marketed through Kremer pigments, and is mighty "spendy". The material is a vinyl-acrylic adhesive, not chemically dissimilar to construction adhesives used to set tile or hang heavy, fabric wall-coverings at a tenth of the cost. I have used these adhesives and so far in testing, they certainly seem adequate. These substrates would not be ideal for a support under raw canvas, although the adhesives would be suitable for gluing pre-primed canvas to a wooden panel, and in this case, a coat of sealer would be necessary to keep the wood from absorbing too much of the adhesive - I believe this is what Julie had in mind in recommending an isolation coat over wood. RSG would NOT be a good choice for adhering pre-primed canvas to any support material.

Using acrylic medium would be functionally very similar, although with an attendant high cost.

??? Who knows what the likely failure modes and life-span for urethane and styrene foams will be? They are essentially stable, the foam makes for a structural cross-section, and they are not susceptible to decay from organic causes, or attractive to vermin. The only thing that seems to degrade them is UV, and that shouldn't be a problem as a support under a painting. I feel any difficulties the stuff will cause will occur long after they've laid lilies over the current generation of painters.

[Thomasin Dewhurst]

Thank-you Julie and Richard for your advice. My paintings are already painted - but unstretched - so I wanted to glue them to a board. The back of the canvas is raw (ish - it may have rabbit skin glue or something on the back - I bought it pre-primed). Could I used rabbit skin glue for that, or is it different for already painted paintings?

[Julie Deane]

Hi Thomasin,

I am sure Richard and I will have different ways to do this.

I've attached finished paintings as well as not-yet-painted, preprimed canvas to wood using PVA glue. The board was first given a coat of GAC100 to avoid any transfer of anything from the wood to the canvas.
I've not had any problems with the art staying firm to the wood.

Here's a link you might find helpful:
http://www.amien.org/forums/showthre...?t=1626&page=2