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Author Topic: Sharp Edges on Stretcher Bars cause cracking on canvas prints...  (Read 4373 times)
philbaum
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« on: May 25, 2013, 11:41:14 AM »
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I'm convinced that early stretcher bars were designed for painters, not for for photographers using already printed canvas.  Sharp edges don't matter so much on painters canvas since the canvas is often primed after installation, causing shrinkage and therefore a tight installation.  

Many stretcher bars you buy often still have sharp edges.  When one stretches printed canvas, some users will blame the amount of force used as the cause of cracks.  But this is not the real problem.  When i started buying stretcher bars from French Canvas (frenchcanvas.com), i became aware that nice rounded outer edges will allow canvas to be stretched without  this tendency to crack.

When i've been forced to buy locally from an art shop, today i'm still getting getting sharp edges (they mostly cater to painters, so weren't much interested in my complaints)  So now i either use a handplane or file to round the edges before assembly.  

I can't say i get perfect quality on the stretcher bars from French Canvas because i still get an occasional warped  bar, mismachined bar, or a sharp edge or two, but i haven't found a company that produces better quaity yet.  But i am glad to hear that French Canvas is going to produce their own stretcher bars in the US using poplar wood.  I think it means better more consistent quality.  Which means less time for me to groom these bars before installation - a pain in the ass :-)

If there are better suppliers out there, please let me know.  I have to admit i have often ruled out suppliers that charge a lot more for their bars - so perhaps thats my problem :-)  Another thing that French Canvas does, is that their bars are often sized 1/8" under on their length, such that the breaks in prints occur on the side of the canvas and not on the front, where they tend to more disruptive to the viewer.  I have found this practice of making slightly undersize bars to work very well.

No, i don't have any affiliation or ownership with French Gallery, just happy to find a supplier that provides a more reliable product.  Also i should note, that their customer service has so far been excellent.

 
« Last Edit: May 25, 2013, 11:45:33 AM by philbaum » Logged
Dan Berg
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« Reply #1 on: May 25, 2013, 12:16:07 PM »
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Three options.
Do like I did and had my millwork firm setup and run my 1/12" and 2" stretchers with the proper radiuses.
Second option keep your present stock and run a small router with a quarter round bit over that bottom edge.
Last option is to find a supplier that offers the bars with the proper top and bottom radius.
I used Decor Moulding out of NY. In the past but the pine was inconsistent in size and needed more of that bottom radius for stretching without cracking.
« Last Edit: May 25, 2013, 12:20:45 PM by Dan Berg » Logged

Paul2660
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« Reply #2 on: May 25, 2013, 03:25:50 PM »
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Larson makes a very good 1.5 inch bar which I use.  Part number 6011 sold in 9 ft lenght.  I also sand down the first edge just a bit to take some of edge out. 

Paul Caldwell
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Paul Caldwell
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bill t.
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« Reply #3 on: May 25, 2013, 03:46:21 PM »
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When last I used stretchers these guys had a good product with excellent consistency and nice rounded corners.  The boxes were also sized for economical shipping.

Just remember, if you cut your own stretchers they will not be easily adjustable to re tension the canvas.

http://linenliners.com/products/stretchers/
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philbaum
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« Reply #4 on: May 25, 2013, 08:21:05 PM »
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Thanks for the replies.  Still checking out some of the suppliers mentioned.  I'd forgotten, but i do have a trim router than i haven't used in a while.  It would make sense to use that for the occasional rounding chore, that might speed things up a bit.

Linenliners has quite the selection of bars, but i'm going to still try to minimize the amount of woodworking i do.
But some of those framing supplies might be useful jobs i occasionally have - a good source.

thanks, phil
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darlingm
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« Reply #5 on: May 25, 2013, 11:24:47 PM »
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OP, dead on.  Before I started stocking lots of mail ordered bars, and larger ones I could cut down to size, I searched every place I could find that sells stretcher bars, and they were all meant for artists with sharp edges.  I don't think many storefronts stock rounded bars.
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chaddro
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« Reply #6 on: May 28, 2013, 03:05:58 PM »
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Dick Blik actually has a decent stretcher bar with keys so you can add tension to the stretch print after.
I've been using them for several years now. They have heavy duty bars up to 96" and also braces.

http://www.dickblick.com/products/blick-heavy-duty-stretcher-bars/

You may have some minor inconsistencies from bar to bar, so I always buy in store so I can test fit before buying.
 
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RFPhotography
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« Reply #7 on: May 29, 2013, 07:55:26 AM »
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Are you talking edges or corners?  It makes a difference.  I've never found a stretcher bar that had a sharp edge (the part of the bar that touches the print).  But every stretcher bar I've looked at does have sharp corners (where the two milled pieces join).  The latter is pretty easily taken care of, if desired, with a power sander.  That said, I've never had a problem with cracking with properly coated prints.  The spray on coatings are useless.  But there are roll on coatings that do a very nice job of sealing the print and preventing cracking. 
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PeterAit
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« Reply #8 on: May 29, 2013, 10:11:42 AM »
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I assume you don't really mean that the canvas cracks, but rather the varnish you have applied? Could that be the problem? I have stretched many prints on bars with 90 degree edges without a single instance of cracking (I use the the Breathing Color varnish). FWIW, my workflow has the stretching done within a day or at most 2 of the varnishing. If the varnished prints sat around a lot longer, perhaps the varnish gets a bit more brittle?

I would not accept bars that are not the specified length. If I want the print to wrap around the edge by a wee bit (a good idea), I will make the print that much larger.
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Peter
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philbaum
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« Reply #9 on: May 30, 2013, 01:35:53 AM »
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I'm talking the edges along the length or width of the bars, not the corners.  And its not the canvas cracking, that would be really bad :-), its the pigment flaking off the creased canvas, minutely - very tiny flakes.

I've been using aqueous polyurethane varnish, exterior, clear, selling for about $20/quart which is probably much cheaper than BC.  I previously was using interior polyurethane and it cracked more frequently, the exterior is definitely better.  Self leveling, dries in less than 2 hours, brushed on coat.  Now i get only a slight amount of cracking in the corner when its folded back on itself.   

I buy my larger prints (larger than i can print that is :-)) from a company that sprays on the varnish.  I don't see cracking in even the corners on theirs, so its either due to a lighter coat or better varnish than i'm using.
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Photopro888
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« Reply #10 on: May 30, 2013, 02:27:35 AM »
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I have tested many stretcher bars (Including French canvas) and the best I have found are from ML Supplies (http://mlsupplies.biz/C-Stretcher-Bar_c21.htm) the edges have the perfect amount of roundness to them. The sizing is always very accurate within a 16th of an inch the corners join so good that they are sharp so I do sand them (by hand) with a sanding block, but it only takes 60 seconds to do four corners.

It looks they may use the same stock from what Bill T recommended (http://linenliners.com/products/stretchers/) but Im not positive on that, so if you dont have your own chop and join equipment this place (ML Supplies) is my favorite for stretcher bars.
 
As far as canvas cracking, I would agree with Peter its most likely the coating (that we put on) that will pull the canvas coating (the coating that the canvas manufacture puts on) along with the ink    the BC coating is good if you stretch in a day or two, but with ClearShield Type C I can stretch months later without issue, this has been my experience after well over a hundred Gallery Wraps.

-Darren
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PeterAit
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« Reply #11 on: May 30, 2013, 07:19:20 AM »
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I've been using aqueous polyurethane varnish, exterior, clear, selling for about $20/quart which is probably much cheaper than BC.  I previously was using interior polyurethane and it cracked more frequently, the exterior is definitely better.  Self leveling, dries in less than 2 hours, brushed on coat.  Now i get only a slight amount of cracking in the corner when its folded back on itself.   

The BC Timeless Gloss or Satin is $90 a gallon, just a little more than you are paying. For some odd reason, the matte is $120 a gallon.
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Peter
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jferrari
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« Reply #12 on: May 30, 2013, 08:08:15 PM »
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The BC Timeless Gloss or Satin is $90 a gallon, just a little more than you are paying. For some odd reason, the matte is $120 a gallon.
Or $107.95 as reported on their website...
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bill t.
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« Reply #13 on: May 30, 2013, 10:57:37 PM »
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If anybody's interested the corner joints on those ML Supplies bars were made with a device called a thumb nailer or thumbnail joiner.  It's not as awful as it sounds, really!  I don't  recommend the technique, but it is a way to join frames without an underpinner, while enhancing your pleasure at generating an even bigger sawdust mess than your saw.  If you are interested in that technique, you should search thegrumble.com where you will get an earful of widely varying opinions.  The best ones aren't cheap and they are as persnickety as you could hope for.
« Last Edit: May 30, 2013, 11:00:34 PM by bill t. » Logged
Dan Berg
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« Reply #14 on: May 31, 2013, 05:27:59 AM »
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Although I have an underpinner my tool of choice has been my hand held v nailer.
Especially with the larger frames. A spot of glue,pinch the joint together with your fingers and shoot 3 nails per joint.
Flip the frame over and another 3 vnails per joint. lightly sand the corners and done.
The vnails pull the joint together so no clamps required. You start with square miters you get a square frame.
I just completed a 30"x40" frame and it took 3 minutes to cut up the 10' lengths on my dual mitersaw and another 5 minutes to staple and sand.Just under 10 minutes from start to finish.
And the reason to make these yourself? The frame was actually 30 1/16" x 40 1/8" the exact face size of the canvas after stretching requires that little difference in frame sizing.

« Last Edit: May 31, 2013, 05:39:17 AM by Dan Berg » Logged

mg73
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« Reply #15 on: May 31, 2013, 08:26:08 AM »
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Dan,

Which V nailer are you using?  How do I get one?
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Dan Berg
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« Reply #16 on: May 31, 2013, 05:17:24 PM »
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It is a Woodtek, available at Woodworkers Supply.
$229.99
« Last Edit: May 31, 2013, 06:06:30 PM by Dan Berg » Logged

rgvsdigitalpimp
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« Reply #17 on: June 01, 2013, 02:09:01 PM »
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Hey Dan, I saw the image of the V nailer you posted.  I didn't know they sold these.  I'm going to purchase one ASAP.  Quick question.  The wooden stretcher bars you are nailing in the picture.  I like the little lip on top.  Where do you get these made? 
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petermfiore
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« Reply #18 on: June 01, 2013, 02:13:30 PM »
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rgvsdigitalpimp,

The lip is pretty standard on Artist stretcher strips. It is there to prevent a brush from striking against the stretcher bar, leaving a phantom mark. Search on Artist stretcher strips , and you should have a good choice.

Peter
« Last Edit: June 01, 2013, 02:18:41 PM by petermfiore » Logged

Dan Berg
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« Reply #19 on: June 01, 2013, 03:55:45 PM »
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rgvsdigitalpimp,

The lip is pretty standard on Artist stretcher strips. It is there to prevent a brush from striking against the stretcher bar, leaving a phantom mark. Search on Artist stretcher strips , and you should have a good choice.

Peter
Their are other good reasons for that top lip w/radius. All manufactured bars have it.(Or they should.)  
I have my millwork shop do custom runs twice a year to my specifications. All the proper radiuses 1 1/2" and 2" deep bars in 10' lengths in Poplar. It is called taking charge of your quality control. Just too many defects coming from my suppliers.
« Last Edit: June 01, 2013, 04:08:19 PM by Dan Berg » Logged

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