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newbie with a question about sealing stretcher bars

josjosjos

Grumbler in Training
Joined
Apr 15, 2020
Messages
1
Hello! I have recently deiced to start stretching my own canvases! I'm sorry if this is not the right place to ask this but do I have to seal my stretcher bars or can I just put them together and start stretching canvas over them? I have seen so many different opinions on the internet about this and figured I would ask here! Thank you all so much!
 

wvframer

Humble Picture Framer
Forum Support Team
Forum Donor
Joined
Oct 9, 2007
Messages
1,526
I don't seal stretcher bars.

If you do want to seal one, use a foil tape. Using a varnish or shellac is not very effective.
 

tedh

SPFG, Supreme Picture Framing God
Joined
Nov 7, 2005
Messages
11,377
Same with what the others are saying.

now, the next issue: do you stretch from the centers of the bars, or do you start at the ends? This debate has been debated. I’d suggest watching the YouTube videos that recommend starting at the centers of the bars.

Good luck!
 

CB Art & Framing

SGF, Supreme Grumble Framer
Joined
Feb 20, 2007
Messages
2,114
If it’s a valuable painting, why not. Some good quality gesso maybe?
CMI has some primed stretcher.
For decorative prints I would not.
Some lower quality material has sap & beetle jokes & comes warped-I would avoid.
 
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wpfay

Angry Badger
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Sep 1, 2000
Messages
10,541
I guess my question is "To what end?".
Good quality stretchers are made from No.1 Basswood which is relatively low in lignin and tannins. Painting them really doesn't seal them if your concern is acid migration. As Greg mentioned, only a metal (or glass) barrier will stop that. Besides, very little acidic gas escapes from the side grain of the wood, it comes primarily from end grain. Normal framing of canvases doesn't trap the gasses, and they are dissipauted before they can do damage. Sealed frame technology works by limiting the amount of oxygen available for oxidation but also has a whole new set of maintenance issues with it. Even with the metalized tape, you are still punching holes in it, effectively breaking the seal, with staples or tacks.
From what I've seen, the primary damage to canvases, other than impact, is weakening of the unprimed linen that is wrapped around the stretchers. Linen has wood protein, Lignin, in it and in the presense of oxygen will slowly self destruct. This area on a stretched canvas in a frame is also an attractive place for bugs and their debris which can accelorate the decay. Painting the stretchers will have no effect on that.
If you have a very valuable canvas to stetch, look at Trimar stretchers. https://trimarstretcher.com/ for some interesting modern technology, or to Simone Liu for more traditional styles https://simonliuinc.com/stretchers/
 

nikodeumus

CGF II, Certified Grumble Framer Level 2
Joined
Apr 21, 2015
Messages
447
I guess my question is "To what end?".
Good quality stretchers are made from No.1 Basswood which is relatively low in lignin and tannins. Painting them really doesn't seal them if your concern is acid migration. As Greg mentioned, only a metal (or glass) barrier will stop that. Besides, very little acidic gas escapes from the side grain of the wood, it comes primarily from end grain. Normal framing of canvases doesn't trap the gasses, and they are dissipauted before they can do damage. Sealed frame technology works by limiting the amount of oxygen available for oxidation but also has a whole new set of maintenance issues with it. Even with the metalized tape, you are still punching holes in it, effectively breaking the seal, with staples or tacks.
From what I've seen, the primary damage to canvases, other than impact, is weakening of the unprimed linen that is wrapped around the stretchers. Linen has wood protein, Lignin, in it and in the presense of oxygen will slowly self destruct. This area on a stretched canvas in a frame is also an attractive place for bugs and their debris which can accelorate the decay. Painting the stretchers will have no effect on that.
If you have a very valuable canvas to stetch, look at Trimar stretchers. https://trimarstretcher.com/ for some interesting modern technology, or to Simone Liu for more traditional styles https://simonliuinc.com/stretchers/
Fantastic answer! I learned more about stretchers in that post than all my years of muddling through on my own. 👍
 
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