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Warping Art Piece

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Forum topic by QuickTooth posted 04-19-2012 11:55 AM 1048 views 0 times favorited 6 replies Add to Favorites Watch
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QuickTooth

8 posts in 996 days


04-19-2012 11:55 AM

Topic tags/keywords: question glue warp mdf

I have been making wall sculptures for a little while that consist of a 1/2” MDF backboard with hundreds of small wood blocks glued to the surface. I started using plywood as a backboard but had to much issues with warping. Using MDF seemed to fix that problem until this last large project I had done for someone warped badley after I sent it to them. This piece is 6’6” x 2’0”.

I suspect the glue could be the culprit but I had this for a few days after glue up before I sent it and it was straight when it left. When I glued this I basically painted the back with glue and then adhered all the blocks one section at a time. Also I used tightbond II and the wood blocks are pine.

So, basically can you think of anything to tell my client as to what to do to fix the warp? Besides laying it flat with some weight on it I am out of ideas.

Also what can I do to prevent this in the future? Different backboard? Different glue?

Thanks in advance!


6 replies so far

View Tyrone D's profile

Tyrone D

314 posts in 999 days


#1 posted 04-19-2012 12:03 PM

How is it hung on the wall?
If it’s a semi-permanent fixture, you could make it so some of the blocks lift up and have screws 16” and 24”OC. All the owner would need to do is pre-drill the studs(If mail-order) and put in screws. The blocks could be friction fit so they don’t fall out. Perhaps even some double sided tape.

Do you put a finish on the back?

-- --Tyrone - BC, Canada "Nothing is ever perfect, we just run out of time."

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QuickTooth

8 posts in 996 days


#2 posted 04-19-2012 12:12 PM

It is hung with a long metal french cleat running the length of the piece. I had though about screwing it as you say to stud with removable blocks before. but the issue is that this piece arrived this way and was warped before even being hung. And yes I apply poly to the back.

Thanks for such a quick reply. My brain is going crazy at the thought of having to redo this, and a couple of others!

View Lee Barker's profile

Lee Barker

2169 posts in 1517 days


#3 posted 04-19-2012 01:32 PM

Interesting problem, well described.

Sometimes wood will react due to internal stresses. We can exclude that here; the pine pieces are too short and the mdf has no grain.

The poly on the back: waterborne or solvent?

My intuition tells me that the convex side would be the side that is taking moisture, but it seems more likely that the moisture would come from the glue.

I have two suggestions:

First, some experiments with MDF. Strips maybe 5 or 6 inches wide and 49 long. Try different combinations.
Could you try a strip of 5/8? It might have just enough integrity to negate the problem.

Would it be possible to glue the blocks on with contact cement?

Second, to repair: I think these will have to be laid on their face and then scored on the back 1/3 deep with a panel saw, just to weaken the backing. An external frame may still need to be applied to the back, but the weaker you can get the backing without taking its integrity, the better. The frame on the back may need to be pieces of solid stock that are actually cut with a curve to them. Dry clamp until you get the right combination of counteractive force vs. the existing curvature. This is an intuitive process, but it will work. The cuts would start an inch or two in from the edges.

I like the artwork, btw.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View Earlextech's profile

Earlextech

986 posts in 1357 days


#4 posted 04-19-2012 03:37 PM

The problem here is quite simple, it’s just like formica. If you laminate one side of a board, it will warp towards that side of the board. You must also laminate the back of the board. A peice of formica might just do the trick and would make the back look finished.

-- Sam Hamory - The project is never finished until its "finished"!

View moment's profile

moment

2123 posts in 1348 days


#5 posted 04-19-2012 06:13 PM

I would assume that the french cleat was not installed on the piece before you shiped it . A metal heavy duty ( non flexible ) cleat,running the length of the work, would not have allowed the warping on both corners as shown . If you had edge glued as well as face glued the individual pine blocks then you would have a very stable structure . Edge glueing may also require that you paint the pine pieces after assembly . The use of large glued up pine or birch ( solid wood panels 3/4 “thickness ) from HD or IKEA have always worked well for me as a backing . Your artwork is too time invested to have this happen by using Cheap MDF or undersized non-hardwood plywood as a backing .

Quick Fix: Call a couple of cabinet shops near where your customer lives and discuss the problem and the cost to fix it. Have the customer deliver it to them and then you can pay the Cab Shop promptly. It is better to lose a little money than your reputation . A timely resolution will appease your customer, hopefully.

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QuickTooth

8 posts in 996 days


#6 posted 04-20-2012 12:04 PM

Thanks for all the responses guys. This non woodworker who has found himself working with wood appreciates it greatly!

Earls analysis seems pretty good for what I was thinking. I think it is more the glue shrinking a little and pulling the board into a warp rather than it warping because of moisture content. And laminating the board is something interesting I will have to consider.

Moment, there was a cleat installed before hand but it was an aluminum cleat that was quite bendable along that direction. Edge glueing all ove those blocks might make something like this entirely to time consuming. It already takes about 6 hours to get all the pieces laid out straight and in order without applying glue to each individual block. But i will consider still if I can apply it.

Also, would birch ply be the best for this? I chose MDF not for its cheapness but for its straightness and thought it would bend less. I think I have seen laminated MDF, not sure, maybe even one sided laminated…that seems good. Any opinions?

BTW, for the quick fix I am heading down there myself to fix the problem. I will be actually removing some of the blocks and attaching it directly to the studs in the wall to force it back in shape. Then reinstalling the blocks with a velcro back.

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