Thread: Any tips on rectifying/preventing cupping of carved wood panels?

I'm guessing that the cause could be one or more of the following

he's carved green wood which has cupped as it subsequently dried

he's put a finish on the carved work but not the back of the piece leading to uneven moisture take-up / loss

he's using flat sawn boards rather than quater sawn ones (flat sawn boards will cup more readily that quarter sawn ones)

he's hasn't alternated the growth rings when glueing up flat sawn boards

the carved piece has been stored/displayed flat against a wall in a way that allows moisture to more easily move in and out of the carving than the back of the board


there's sure to be other suggestions

ian

Exactly as Ian has stated.... I concur.

The relief of the carving eliminates any wood to expand or contract so when the back acclimates to the weather and conditions it is free to move and will grow in size whilst the relief side has no where to go and will remain the same. Sealing the back as well as the front will retard the seasonal movement but will not completely stop it and needs to be secured in a frame or casement to hold the panel flat whilst it influxes the moisture. (or lack of moisture)

Wet the panels with water,
Lay them hollow down on a flat surface.
Put a weight on top, (be careful too much weight may split the board)
Wait until dry (a few days)
If the board is still cupped repeat the treatment (possibly a few times)

After you eventually get it flat and dry its necessary to seal both sides with a varnish or lacquer or shellac. Oil is useless as it doesn't stop the timber taking moisture from the atmosphere. You also need to frame the back of itto allow for timber movement but prevent cupping.

Hey Bob... I just read this thread and the other day I noticed that my keel timbers have begun to move... so these are Kapur 8in x 6in x 16 - 20ft and have started to bow one in particular (longest ) Ive tried layin them cup side down with weight on top but that hasnt worked... Im starting to think that I may be better off cuttint them in half length ways and going from there? perhaps then laminating the keel from the sliced lengths... can be done but would rather them in one peice

(the woods dry as by the way)

Thanks you gents . I have taken all of the comments on board, and have included a couple of pics below to demonstrate the extent of the problem.

Ian, the timber he has used is one of the Asian (meranti?!!) species which was kiln dried abroad and stored locally for 18 months prior to use, so green timber is not the problem. He has indeed put a stained wood-wax finish on the carved face & nothing on the reverse, so this could be part of the problem. Hard to accurately pick the growth rings on this stained meranti, but the sawing method & growth ring placement could be factors as well. It is designed to be hung on a wall, so your observation on moisture movement in the front vs back may have some merit as well, particularly in a heated room?.

Hickory, comments noted - thank you.

Echidna (Bob), I had in mind to try the water inundation method followed by a bit of "sun baking" to the rear of the panel. I will also use your recommendation of some weighted persuasion during the drying process. I am also considering the introduction of a framed perimeter (steel angle or similar timber?) to the panel.
I am also interested in your comments of oil versus varnish/lacquer as a sealant, and the resultant effects on the timber. Does the group concur?

As you will all see from the photos (if they work) the panel is deeply concaved to the face. From experience, this always seems to happen to some extent because of the lessened face thickness & profile which allows the full depth rear face to retain more moisture, and gives the face a little more air exposure. However, the resultant curvature would seem somewhat severe given this factor alone.

If this is considered a matter of interest to others I will post some further results & photos of the attempted rectification process. The work itself is too good to abandon, I think.

Attachment 25065 Attachment 25066

Thanks. Wayne

Originally Posted by Hardenfast

I am also interested in your comments of oil versus varnish/lacquer as a sealant, and the resultant effects on the timber. Does the group concur?

As you will all see from the photos (if they work) the panel is deeply concaved to the face. From experience, this always seems to happen to some extent because of the lessened face thickness & profile which allows the full depth rear face to retain more moisture, and gives the face a little more air exposure. However, the resultant curvature would seem somewhat severe given this factor alone.

If this is considered a matter of interest to others I will post some further results & photos of the attempted rectification process. The work itself is too good to abandon, I think.

Attachment 25065 Attachment 25066

Thanks. Wayne

Take note of what the pros in the group say,
They are more likely to have experienced these problems and permanent solution than many of the other members.

There is absolutely NO WAY I would EVER use an oil finish on bare timber, if it is sealed so it is impearmeable to moisture ingress/egress , that's another matter.

The face has lower moisture level than the back as the front has shrunk more than the back. Some simple timber cleats screwed on the back (in slotted holes) once its flat again, should hold it ok. Get rid of the oil wax finish and use varnish/lacquer/shellac etc. You can always wax over that.