I am conserving a vintage frame constructed of pine, where the mitered corners have developed gaps as wide as 1/4″ and where the frame has warped to about 2″ from flat. It is a heavy 36″ x 34″ frame. The frame had 3/4″ pine planks professionally tapered and glued to the back on all sides.
I had to removed the backing planks to enable closing the gaps on the mitered corners. When I removed the backing planks, the warping was corrected.
I would like to leave the backing planks off once the frame is properly repaired, but if they were part of the original frame fabrication, I should probably reinstall them. If they were added later to stabilize or strengthen the frame, I would likely leave them off.
I believe the frame was fabricated before 1950. It frames a hand painted copy of Hals “Baffoon Playing a Lute” that was possibly painted between 1880 and 1900.
Question: Do you know of a framing technique where planks are glued and nailed to the back of a frame to provide structural strength, either during original frame fabrication or to stabilize a frame at some later date?
Any recommendations would be appreciated.
Frame Front.jpgFrame Backing Plank Construction.jpgFrame Corner Misallignment 2.jpg
Thank you for your expertise, Martin.
I errored. The planks are exactly 1/2″ thick. I attached photos.
I am not an expert on evaluating dried glue, but I put a drop of water on a spot of dried glue on the back of one of the boards. In a couple of minutes it became sticky but did not dissolve completely.
The addition of heat cause the water soaked spot to dissolve immediately allowing me to easily scrape the spot down to bare wood. Heat also caused other glue areas to bubble up immediately.
I suspect the planks were attached with hide glue and nails, but your expertise would be appreciated.
I had to shave a minimum amount from the mitered corners to get them as square as possible, so I cannot assess the glue used in the joints. I used steel mending brackets on the back of the corner joints to minimize the affect of the slight bowed and warped frame boards during reglueing. Getting the corner joints “perfect” was impossible. But, after reglueing, the frame looks very good.
I am concerned stress from the warped and bowed frame boards will cause the joints to fail over time. I plan to insert a wooden dowel in the thick part of the frame near the outer edge of each corner for added strength.
Should I strengthen the inside of the corner joints with a bracket? I have considered countersinking a small metal mending bracket across the joint using flat head screws to keep it flush with the back of the frame boards. Your expertise and suggestions will be appreciated.
The frame seems to be very strong, so I don’t plan to replace the backing boards. I typically use hide glue for my repairs.
Any help is appreciated.
Have a great day and stay safe!
Frame Backing Board.jpgBoard Back with water drop on glue.jpgGlue spot after water removal.jpgGlue spot after water heat and scrape.jpg
I have seen backing planks like you describe, but usually they were ¼” thick and were placed there not to strengthen the frame but as a protective backing.
Some “High End” artist stretchers in the late 19th century were fabricated with panels within the stretcher to protect the canvas and today in most museum we attach single wall corrugated or foam core boards but this is to protect the artwork not strengthen the frame. Also in the 19th c. there was a semi water proof papers used as a backing protection, used usually when paintings were sent abroad on ships even though they were in crates as moisture protection.
You do not describe what the miters were adhered with, animal hide or a PVA adhesive and, if a PVA, whether the old glue had to be removed and a better adhesive used? Epoxy works as a sealant to the wood so the future joint will always be compromised. I would not replace those planks but photograph them as you had found them as an (archival record) of the frame treatment. It is possible that the random laying of the wood planks were not fully dried and because they were glued and nailed, cupping or warping or just simple expansion followed and because the planks were fixed the pressure went to the weakest place the miters. If you feel that you need to replace the planks I would consider edge planing for future expansion, no glue and screws only or better replace with ¼” or 3/8” plywood sealed on both sides (using an acrylic or polyurethane coating) and screwed to the back of the frame.
Martin KotlerFrame ConservatorSmithsonian American Art Museum
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