Help! Sagging Linen!
 

I have a LINEN canvas that keeps sagging. I have tried many tricks, re-stretching for one, lightly misted the back with water and let dry and used stretcher keys.
Does any one have a suggestion on how to tighten stretched LINEN that sags? I have heard that misting the back with rubbing alcohol works. Does any one know anything about that or if it works??? :bewildere
Thanks!
Lisa

I've had that happen and I've had to restretch it. I keep the corners attached to the stretcher bar so it doesn't get out of alignment and then I remove and re-staple it section by section in the same order as if I was stretching a new canvas. Pull as tightly as you can.

You can avoid the problem somewhat by storing the linen in a warm dry place and by only stretching it on a warm, dry day (not always an easy thing here in Seattle!)

I haven't had much problem with this since I bought some serious($100 !!) molybdenum canvas stretching pliers. It seems that the first time I stretch it is sufficient, most of the time.

I personally wouldn't spray anything on the back of it.

Hi Michele,
Thanks! I have re-stretched it three times already!!! uuuuuuuuuuuuuu
It starts of quite nice and tight and then gradually loses that tightness. It is so humid here in Atlanta and I have this problem on occasion but not this bad. I even set it up next to a space heater but no luck.

I have been stretching my own linen for 16 years now and have NEVER come across a problem like this one. If I hadn't already started the commission and gotten so far into it I would start over.

Thanks again!
Lisa

Lisa--

Search this site, as there are other threads addressing this problem too.

I've had the same problem, and it's somewhat endemic to where we live. Most of my paintings sag a little when the season changes to winter and the humidity goes down. But if you restretch and over-tighten, when summer comes the canvas almost hums it's so taut. Usually when the paintings live in the same space for a year, they stop changing so drastically. I don't know how much sag you're getting, but use caution due to this seasonal variance.

Bill Whitaker has suggested stapling foamcore to the back of the stretchers, to even out the changes in humidity over time (protects the painting too). Others have sealed the back of the canvas itself with various preparations, but I'm somewhat timid to do so. It may be perfectly fine.

I especially wouldn't use alcohol...except to ply the artist.

Maybe it's time to mount it to a panel. In Kevin McPherson's first book he has good step by step instructions on how to do that.

Thanks Tom & Michelle! I will search the forum again but I think Michelle is right, I need to just mount it on panel. aaaarrrgghhh!
Lisa

Was this a canvas you stretched and primed yourself, or was it pre-primed roll canvas which was mounted on stretcher bars?

Correctly done, a "home-made" canvas is usually more stable than those made up from pre-primed roll stock. As Tom notes, seasonal changes in ambient temps and humidity normally affect linen, and adjustments made in "slack" times may be too much. It's actually the major complaint against using linen, which seems most prone to be affected by climate change, and depending on the locality where you live, and where your paintings may be placed, other fabrics may be a better choice. Polyester is incredibly stable and unaffected by changes in the weather. Hemp is also far less reactive than linen.

As Tom notes, Bill Whitaker's suggestion to insulate stretched canvases from behind will not only ameliorate seasonal sagging, but will greatly extend the life of stretched canvases generally.

Perhaps spraying alcohol on the backside of a sagging canvas would re-shrink it, but I think that would only depend on the water content of the alcohol. Rubbing alcohol has a considerable percentage of water in it. Spraying the back with plain water would be a temporary fix, as the canvas is certain to sag once again when that added water has dried. Using an alum solution for the spray can be effective and "permanent" if sagging is minimal. A tablespoon in a pint of water works well. Alum will considerably toughen the glue size.

Mounting to a panel can be problematic: what kind of panel should be used? What kind of adhesive to use? Mounting to a panel may also obviate the main (only?) advantage of painting on a stretched canvas, i.e., the light weight of larger pieces.

Hi Richard,
Thanks for that. The linen is pre-primed which I cut and stretched myself, as I have been doing so for the past 16 years. It was nice and tight when I originally stretched it months ago. It sagged a bit and I tightened two sides. Now it is sagging again. The sagging isn't obvious, no ripples or buckles it is just very floppy when I paint on it.
Where can I find Alum?

Lisa,

How big a canvas is it? There are other options, depending on the size.

Hey Julie,
It is a 30x40

Short How-To
 

Lisa,

If you don't mind the weight, you can glue a thin piece of furniture-grade plywood to your stretchers and then glue the linen to it. I've found good success in doing that with smaller pieces, but I'm not sure how the weight would be for 30 x 40. You could try getting the local lumber place to custom cut you some out of 1/4 inch to see (you might need thicker for this size canvas). You will need to add some bracing.

Here are a few links that I have found helpful:

http://www.ampersandart.com/featured...ed-artist.html

http://www.amien.org/forums

I'm working my way up to the larger sizes (only done to 16 x 20 so far), so I haven't tackled a 30 x 40 inch canvas - yet. I feel it is helping my skill level to practice first. My first attempt was pitiful, but the improvement was rapid. You also might want to try your hand at some smaller sizes to get a feel for the task before doing this large a canvas.

For my 16 x 20 inch canvas, I glued my plywood panel to my stretchers. I used Golden's GAC100 to seal the plywood. I also made sure that my pre-primed linen was smooth on the back - I found that if I didn't use something like sandpaper to smooth off the nubs, they would show through on the front. I then applied Lineco archival glue to the panel, flipped it over and positioned it on the linen, turned it back so that the linen was facing upright and used a 6 inch wide brayer to get the linen smooth. I then weighed it down with a board and heavy weights and let it dry overnight. It came out very nice - the surface was perfectly flat: I folded and stapled the linen around the sides of the stretchers like I would normally do with a canvas.

For the Dibond, you would need to research the right type of primer to use. I thought I had that info, but can't lay my hand on it at the moment.

If you need to get a piece of Dibond quickly, I have two 36 x 48 pieces and I will be happy to sell one to you for what I paid. I'm about an hour north of Atlanta.

Hope this helps.

There are some other threads re: applying canvas to panels, and some methods get very exotic, such as aircraft aluminum, etc.

To Richard's point, I did my first portrait on canvas adhered to masonite, a 30x40 canvas (a "moderate" size), and it weighed a bloody ton. Haven't done it since.

Interestingly, Scott Burdick painted a demo here in Greensboro this year, and he is painting on canvas adhered to "gator board," a stiffer, harder version of foamcore. It's extremely lightweight and stable. He has done some very large paintings on this material, and they come to him with the canvas already applied. You might want to e-mail him and ask what manufacturer they come from--memory fails me now. And if you want to resize the canvas slightly, you don't have to restretch it, you can just cut it down.

Alum? Look in the spices section at your supermarket. McCormick packages approx. 2 oz of alum in a small jar . . . kind of a rip for the price asked for that amount, but then, you don't need much. Your local pharmacy may also have it.

Gatorboard is certainly a workable choice for panels to use for canvas supports. Available in 4'x8' sheets in thicknesses from 3/8" to 2", it's amazingly flat, rigid, stable and light in weight. Only drawback I see is that styrofoam core, which won't add much Old World ambience to perceptions of what a "fyne arte" oil painting should entail . . . you'd probably want to camoflage this aspect for the sake of your clients' peace of mind . . . styrofoam has a way of being negatively associated with fast-food packaging.

I believe "New Traditions" is one maker of canvas panels on foamcore board.

Lisa,

Alcohol on an oil painting is definitely a bad idea! There is a product called Tight'n'Up that works very well for tightening slack canvases.

Gluing the canvas to a rigid panel is probably the best thing, if you do it right.

Virgil Elliott

Hi Lisa,
I just happened on this thread and realize that my response is coming about a year late.
I had the same unfortunate experience a few months ago when I noticed that the canvas on a commissioned portrait was sagging. I was to deliver the painting two days later. Mine was painted on a pre- stretched canvas, 20 x 24. I found a lot of great input but none that worked for my timeframe, so in a panic I decided to try the quickest fix that I found. I have to tell you that I was terrified at the thought of doing this and I'm sure that it is not the best or safest method...but it honestly worked and the canvas remained tight. The instruction that I found online said to heat a pan of water to boiling, pour it into a bowl and using a clean, natural sponge, quickly and 'lightly' wet the back of the canvas...and immediately dry it with a blow dryer. It was an instant fix...not one that I'm proud of, but will probably do again as panic seems to frequent my studio :-)

I'd be really terrified to use water that hot. Oil paint is remarkably resilient, but anything has its limits. I'm not sure I understand the logic of using hot water. Maybe it affects the fabric sizing or something.

In a pinch, I've misted water onto the back from a plastic bottle/ plant sprayer. Room temperature. Also, I've let it air dry after, with a good result. Some folks would object to water at all, and they may be right, I don't soak the canvas down under any circumstance.

If the canvas was reasonably tight, again, time will lessen the expansion/contraction, but I understand that kind of pressure in a commission situation. Also, not moving it from place to place helps, once it's hung...I've had them slacken from the framer's to my studio in certain seasons. Once it figures out where it's to live, the painting will settle down.

I absolutely agree Tom, this was a risky process, not one to use if there are other time tested options available. I should note that I paint fairly thin as well and I'm not sure of the effect this might have if one were to have heavy paint on the surface.
Drawing on my vast knowledge of laundry :-), I do understand that hot water and a hot dryer are more likely to shrink most natural fabrics. The temperature of the water did seem to be key and I can't agree more that this shouldn't be a process in which the back of the canvas is overly wet, it should just be a light touch with a damp sponge to dampen the canvas.

No harm, no foul, as they say... :thumbsup:

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.

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?

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.

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

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?

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

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.

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!

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.

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.

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?

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

Pre-primed canvas or gluing finished painting to a panel, use acrylic gels, vinyl-acrylic adhesives, PVA or whatever turns your crank.

Gluing raw canvas to a wooden panel, you first tack the canvas to the panel, then saturate it with RSG from the front, this works well, and nothing will "transfer" to the canvas from the wood (?) because it's isolated by the glue. You can't do this with a pre-primed canvas or a finished painting, and while it is theoretically possible to use RSG for that pupose, it isn't the easiest stuff to use this way, and is not an appropriate adhesive to use over aluminum, or sealed wood.

Julie, just curious . . . what elements do you perceive "transfer" from wood to canvas, permeating an adhesive layer ? I know some plywood glues contain formaldehyde and other volatiles which may migrate or "off-gas", possibly reacting with other materials, but any solid woods suitable for the purpose (properly cured cabinet grades)are pretty much inert. Poplar panels were preferred from pre-Renaissance times by reason of several advantages that species presents for this application (broad planks, machineability, fine grain, low resin content, and optimal acceptance of glues and paint coatings.

Richard, I don't know a lot about all this, so I'm just following advice I've read and being extra cautious.

According to the Amien site:

GAC 100 is an acrylic dispersion medium developed to prevent SID ("Support-Induced Discoloration), wherein the application of an acrylic dispersion ground -- around 50% water at the outset -- can dissolve organic materials in the fabric support and cause them to migrate into the drying ground and discolor it.

So I got it backwards: it's not from the wood to the canvas, but vice versa.

Thanks, Julie. That's interesting. What I gather from this, is that it is possible water-soluble contaminants/colorants inherent in a canvas could come into solution when an acrylic, water-soluble ground is applied, which would present as discoloration, or variegated stains or watermarks in the painting ground. The sealer you recommended (GAC 100) is a product intended to "pre-prime" a suspect canvas before applying an acrylic painting ground, to prevent any such discoloration.

Going back several responses in this thread, I'd say that the best prevention for this fault would be, as noted, wash your raw fabrics before stretching and priming them! .

I don't think one need worry at all about anything on a wooden panel discoloring either pre-primed canvas (especially oil primed) or a finished painting, although the sealer could be useful to control the absorption of PVA or acrylic adhesives by a raw wooden panel. ?? In any case, it sure can't hurt anything . . .