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Author Topic: Gallery wrap canvas buckling, stretchers, and re-tensioning  (Read 1281 times)
del@pscc.com
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« on: March 04, 2014, 04:37:48 PM »
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We have produced and sold many gallery wrap canvases, both large and small.  Small (e.g., 8x10) canvases seem to retain their tension but larger canvases are prone to buckling, either seasonally or with long-term changes in ambient temperature and humidity.  While canvases can be tightened or re-stretched, that is a practical solution only for large collections of canvases, such as exhibitions, where several can be adjusted in a single trip.  It is not a solution for individual canvases hung on customers' walls or shipped to distant locations.  Even if it was possible, the need invariably to touch up spots where ink cracked or popped off during adjustment further complicates the matter.   And this is all made worse by the fact that we are addressing photography, not high-value oil paintings for which the cost of a "touch-up" visit might be a minimal portion of the original sales price or value of the canvas.

All of our stretchers use mitered slip joints at the corners.  For larger canvases we also install cross braces as well as either wooden wedges or turnbuckles to facilitate future adjustment.  In addition, we varnish each wooden stretcher before assembling frames and stretching canvas, thus assuring that archival standards are maintained.  But for individual, moderate size canvases, this is not much help -- the only solution seems to be replacement, and even that is no guarantee, depending on the ambient temperature and humidity.

We looked into various stretcher designs and have concluded that we are already using the best there is.  Even Wunderbar (not available in the US) or other sprung-corner, patented designs do no more than to impose some initial tension on the corners.  Although marginal adjustments can be made with turnbuckles and wedges, the canvas still needs in most cases to be unstapled and re-stretched in order to compensate for later buckling.  Would a different method of attachment be less likely to accentuate problems?  For example, a method by which the canvas was attached only to the center of each side, (or not attached at all), but held under tension between the center and the ends of each bar, with some kind of spring tension arrangement allowing the canvas to move along but not across the stretcher bars.

One other possibility is that manual stretching is itself at least the partial cause of later problems.  Are machine-stretched canvases less prone to objectionable buckling?   

Does anyone have constructive suggestions or a better approach?

Dave.

By the way, a useful reference is Steven Saltzyk, Art Hardware, the definitive guide to artists' materials, Watson-Guptill, 1987
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bill t.
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« Reply #1 on: March 04, 2014, 05:16:40 PM »
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While I have not wrapped canvas recently, I have several pieces in the field some of which were hand wrapped, while others were machine wrapped.  Bottom line: the machine wrapped canvases are in much better shape several years down the road, with very little of the sagging and rippling issues that have crept into many of the hand-stretched canvases.

All those canvases were  very well braced with crossbars, perhaps more than I really needed, and that extra bracing perhaps took good advantage of evenness of stretch you get from machines that can handle one full side in a single stretch with very consistent tension everywhere along the edge.  I can only recall one instance of "adjusting" a slack machine stretched canvas, but several cases of tightening hand stretched ones, or talking somebody through the steps over the phone.  The machine canvases were all wrapped on rigid, mitered basswood stock from Linen Liners.  The hand wrapped ones were all the adjustable corner type.  Go figure.  Maybe 3" wide rigid stretcher bars are less problematic that 1.5 to 2" adjustable stretcher bars.

If you hand tension canvas in many steps working from the center towards the edges, there is a tendency for things to get tighter and a little out of control as you approach the edges.  This invites various kinds of buckling, as well as the classic syndrome where there is a lot of ripple radiating out from the corners, and buckling towards the center bottom.  In any case, it's very difficult to maintain consistent tension across an entire side while manually stretching a large canvas.  That consistency of tension over an entire edge is one of the places machine really shine, in addition to raw speed.

The machine I used was a manually operated Join Rite and I found it very well designed and easy to use.  I had a 60" and a 36" section joined together to handle (almost) 8 feet.  It came to me very used, beat up, scratched and a little warped, etc. but still worked like a champ.  I liked that I could feel the tension develop as I worked the canvas, although you might get a somewhat more consistent tension from machines that apply tension via adjustable, regulated shop air.
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Paul2660
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« Reply #2 on: March 04, 2014, 07:15:11 PM »
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The machines will give you a more even pull as they are grabbing one entire edge at a time.  You still have to be care on pressure as you can pull on the canvas too much and it will start to separate especially at the top(face) of the print where it first goes around the stretcher bar.

I don't use the adjustable corners etc.  I use a 1.5" fir bar from Larson part number 6011.  This is sold in 9 foot lengths and I have a contract with a local frame shop to have it chopped and joined.  I will use a center support on 24 x 36 and larger.  On 40 x 60 and 36 x72, I do add a corner support but it's not adjustable.  These frames are all joined with a v nailer/glue process just like a standard wood frame. 

For the stretch, I switched to the Bull Dog pliers that have the teeth and are built around a set of pliers that look like vise grips.  I can't say enough about just what a difference these make.  You have so much more control over the piece, and are working 4.5" of canvas at a time.  Prints that are finished with these pliers are drum tight, with no ripples. 

Are you going to get a bit a sag over time, sure.  It's canvas and it will take in moisture from the air and will react to cold/warm, more/less humidity.  However what small amount of slack develops, is not a show stopper and has never had to be re-worked.  For a hand stretch, the Bull dog pliers are the way to go.  If you are doing a large number of canvas prints/stretches, then the canvas machine is the way to go.  They are expensive and take up a lot of room in your studio/shop.  I don't do enough canvas prints to justify it. 

This link is to a article I wrote about the pliers I am referring to.

http://photosofarkansas.com/2013/03/14/031413-review-of-the-breathing-color-stretch-relief-pliers/


Paul C.
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Paul Caldwell
Little Rock, Arkansas U.S.
Photography > http://photosofarkansas.com
Blog> http://paulcaldwellphotography.com
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« Reply #3 on: March 04, 2014, 07:26:12 PM »
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These spring-loaded stretcher bars: http://www.wunderbars.com/ or flat-mount the canvas.

SG
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del@pscc.com
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« Reply #4 on: March 05, 2014, 12:36:07 AM »
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Thanks for the quick responses.

It's interesting that both  bill t. and Paul2660 point out the potential advantages of using a stretching machine.  I'm inclined to see if I can try one out.  I see that Lexjet now carries the Studio Canvas Master ($2950), WholesaleArtsandFrames has the Canvas Stretching Machine ($650), Gilderspaste has the Quickmate stretcher ($738), PILM has the Tendy ($???), and JoinRite has the Canvas Stretcher ($1650).

Any others or recommendations for/against these?  Anything comparable to Wunderbars available in the US?

Dave.
 
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shadowblade
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« Reply #5 on: March 05, 2014, 01:15:47 AM »
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Thanks for the quick responses.

It's interesting that both  bill t. and Paul2660 point out the potential advantages of using a stretching machine.  I'm inclined to see if I can try one out.  I see that Lexjet now carries the Studio Canvas Master ($2950), WholesaleArtsandFrames has the Canvas Stretching Machine ($650), Gilderspaste has the Quickmate stretcher ($738), PILM has the Tendy ($???), and JoinRite has the Canvas Stretcher ($1650).

Any others or recommendations for/against these?  Anything comparable to Wunderbars available in the US?

Dave.
 

Why not just order Wunderbars from the UK?
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jferrari
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« Reply #6 on: March 05, 2014, 07:32:52 AM »
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Tight is tight. Whether from pliers or machine. You are up against the laws of physics. Wooden stretcher or strainer bars are hygroscopic and will change their dimensions with changes in relative humidity. You can mitigate sagging canvas to a small extent by kiln-drying your bars immediately before stretching your canvas. The correct solution is to not stretch your canvas prints at all. A quick search of dry-mounting will provide hours of entertaining reading. Actually, Bill T. has written some excellent posts on the subject. I'd start by barking up that tree.
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John Nollendorfs
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« Reply #7 on: March 05, 2014, 04:16:29 PM »
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Thanks for the quick responses.

It's interesting that both  bill t. and Paul2660 point out the potential advantages of using a stretching machine.  I'm inclined to see if I can try one out.  I see that Lexjet now carries the Studio Canvas Master ($2950), WholesaleArtsandFrames has the Canvas Stretching Machine ($650), Gilderspaste has the Quickmate stretcher ($738), PILM has the Tendy ($???), and JoinRite has the Canvas Stretcher ($1650).

Any others or recommendations for/against these?  Anything comparable to Wunderbars available in the US?

Dave.
 
Dave:
The WholesaleArtsandFrames machine can not do gallery wraps. I myself have machine similar in design to the JoinRite, and love the design because of the open ended aspect. My machine is only 30" wide, but I have done 60" wraps, using the machine to do the center, and then hand stretching the corners with a regular set of stretching pliers. I highly recommend that type of machine as cost very effective for smaller operations. Remember the JoinRite 36" model is only $1,095. probably adequate for up to 3'x4' frames.
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rgvsdigitalpimp
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« Reply #8 on: March 08, 2014, 03:50:45 PM »
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I agree with Paul on those pliers.  I bought them before BC took control of them straight from the designer.  I can't rave enough about how good this tool is.  Extremely tight results.  I have a couple prints on my wall and at customers homes about 3yrs old and are just as tight as when first wrapped.  Just my opinion. 
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Mike Guilbault
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« Reply #9 on: March 08, 2014, 09:39:50 PM »
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I also use the Stretch Relief pliers and love 'em.  I find I need about 3/4" more canvas than normal for the teeth to grab the canvas, but I get drum tight stretches every time.  I also used keyed stretchers so when the humidity changes, the canvas can be tweaked to provide a tight stretch with a couple taps of a small hammer which the client can do themselves. They're a little more money than the simple strainers, but easily becomes a selling feature.
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Jason DiMichele
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« Reply #10 on: March 10, 2014, 05:56:05 AM »
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I also use the Stretch Relief pliers and love 'em.  I find I need about 3/4" more canvas than normal for the teeth to grab the canvas, but I get drum tight stretches every time.  I also used keyed stretchers so when the humidity changes, the canvas can be tweaked to provide a tight stretch with a couple taps of a small hammer which the client can do themselves. They're a little more money than the simple strainers, but easily becomes a selling feature.

+1. And if the stretcher bars you speak of are from Upper Canada Stretchers they are also built extremely well aside from being keyed.
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Jason DiMichele
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