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post #1 of 9 (permalink) Old 05-03-2013, 07:02 AM Thread Starter
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Default Winter dry air problems

I had built a 3.5 x 3.5 ft coffee table out of reclaimed barn floorboards which turned out very well. The boards were jointed. glued and Kreg pocket screwed together for an (almost) perfect finish. However, the air in the house was unusually dry this winter and some of the glue joints are showing slight separation. Not enough to really piss me off but enough to be visible.
Any thoughts on repairing the damage? Do I have to disassemble the table and just reglue and screw it back together or should it be rejointed and then reglued? I don't want to have to refinish the top, if possible.
Any thoughts/help would be appreciated.
Thanx, David
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post #2 of 9 (permalink) Old 05-04-2013, 10:51 AM
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Hey, David; that's a strange issue you're having(?)> It should have worked the other way 'round.
Normally one would try and achieve the lowest moisture content as practical; shrinkage results from the wood drying, not absorbing moisture.
One would have assumed the wood would swell as the relative air humidity.
Are you sure your interior was as dry (relative humidity) as you think it was?
Keep in mind what's going on outside may not translate to the interior conditions if your home/shop are tightly sealed up and you have a family taking showers, doing laundry, breathing, cooking, etc...that's a lot of moisture being introduced.
Sorry, that didn't answer your question.
Another member introduced the subject of Kreg-screwing boards together to make up a panel. The question was asked 'Why are you screwing the boards together, rather than jointing, gluing and clamping (with alternate joints being suggested)?'
In my own opinion, screwing adds unnecessary stresses in directions not desired in a glued panel. The boards will break before the glued joint, in a properly assembled panel.
Can you post pictures of what the separation looks like? Is it related in any way to the screw locations?
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post #3 of 9 (permalink) Old 05-04-2013, 10:52 AM
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Oops...
"One would have assumed the wood would swell as the relative air humidity."
Add "increased" at the end of the sentence.
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post #4 of 9 (permalink) Old 05-04-2013, 02:18 PM
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David it is hard to give a proper opinion without seeing it but, wood is subject to movement if the moisture content of the air changes, that is unfinished wood, after any item is made then proper polishing/sealing should stop that, the thing about polishing is this, to effectively close of the effects of moisture levels changing then you have to polish all the exposed surfaces, and that means under the top as well, it means inside drawers and under them and their backs as well and inside cabinets and over the drawer runners (if they are wooden that is), any spray sealer should normally be good enough, that is you do not have to polish the inside of an item to the same finish that you have achieved on your seen areas but it has to be closed off and under table tops is as important as the seen areas. So if there are areas of your item that are not properly sealed then the water in the air will keep entering the item through those surfaces and expansion/contraction will keep happening as the ambient local moisture level wanders up and down and it would be worse if you do have very dry to more wet ambient moisture levels, now having said that then your joint should not be opening up, without seeing it I also cannot say what happened so what glue did you use and did you spread it around and glue up the joint completely and what joint support (loose tenon, tongue and groove, dowels, biscuit joints) did you use? Glues are not all the same and you have to use a glue that works, do some test joints, if the glue was not effective then the join can move around but when you do a proper glued joint theN the wood should break before the join does, there are many spectacular glues these days that "do not let go" and when you make widening joints in a top, and I think that this is the jointing that you are referring to, then you have to do the best damn joints and use the best glue that you can, I will say that even if you did not use joint support, like dowels or tenons, then a straight but joint should still be very strong if the join is done to meet properly and if the glue is suitable, and the item is properly sealed up inside and out. I hope that this helps and if you want my professional opinion then strap the coffee table to your back and catch a flight to Sydney Australia, Mascot International Airport has excellent coffee and you can have some as I have a look at it so I will meet you there.

Don't ever forget that working with wood is fun but sometimes it is not that funny. NGM

Last edited by neville9999; 05-04-2013 at 02:23 PM. Reason: I left out an n, I hate a then that is typed as a the
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post #5 of 9 (permalink) Old 05-04-2013, 09:14 PM
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"Proper sealing/finishing" does not stop moisture from entering or leaving wood. Popular misconception! Slows it, but doesn't stop it! If it did, wood movement would not be the issue that it is!

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post #6 of 9 (permalink) Old 05-05-2013, 01:07 AM
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David
You did not explain where you build the table outside in a uncontrol tempature area or dry control area. Also table manufactures usually do not finish unside of tables helps control humidy level. If you moved the table inside after you finished it, it would continue to dry
It properly will not be a problem if all glue joints run Parallel to each other when humidity goes up the joint will tighten. Also agree with Dan about screwing panels together
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post #7 of 9 (permalink) Old 05-05-2013, 07:22 AM Thread Starter
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Thanks, all, for the comments.
1. the table was assembled during the summer in my garage (normal summer humidity)
2. The inside of the house was exceedingly dry this year (broken humidifier)
3. the underside of the table was NOT sealed.
4. with Spring here (?) and Summer coming,perhaps things will tighten up again.
5. got a feeling I relied too much on the Kreg screws and may have starved the joints of glue. Guess I'll stick to dowels and/or biscuits for panels.

Would sealing the underside (at this point) do any good?
Because of the dark tone of the wood, pictures are going to be difficult, but I'll give it a shot and post soon.
Thanx again, David
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post #8 of 9 (permalink) Old 05-06-2013, 04:37 AM
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Quote:
Originally Posted by Skyewalker View Post
Thanks, all, for the comments.
1. the table was assembled during the summer in my garage (normal summer humidity)
2. The inside of the house was exceedingly dry this year (broken humidifier)
3. the underside of the table was NOT sealed.
4. with Spring here (?) and Summer coming,perhaps things will tighten up again.
5. got a feeling I relied too much on the Kreg screws and may have starved the joints of glue. Guess I'll stick to dowels and/or biscuits for panels.

Would sealing the underside (at this point) do any good?
Because of the dark tone of the wood, pictures are going to be difficult, but I'll give it a shot and post soon.
Thanx again, David
David as I said it is not possible to give a full opinion without seeing it, you did not say how you did the joint or how close the wood met, or what the gap filling properties of the glue used is as some glues can fill big gaps without much loss of strength and some lose strength with a very small gap so if you care to spend the time then do a similar join the same way with the same glue and let it dry then load up the join and see if it opens under load or not, but I will reaffirm that a properly constructed butt joint that is glued with a suitable glue should not break under load and the wood should break before the join will break and most of what I have said before is about best conditions and best methods, but I am not surprised that you have said that the top was not sealed underneath, my opinion about sealing the tops underside comes from me being an award winning Professional Cabinetmaker with nearly 40 years of making widening and other joints and anyone who makes a wide timber top out of solid wood had better use properly seasoned and tested wood of a known and suitable moisture content and then seal it up over and under, look at all those old tables with cracked and split planks and you will see the proof there. About sealing it up now, doing that will not undo the situation as it is, it will not fix the failed joint so you will have to decide if you leave it as it is and let it age with grace as those tables also look very nice to me, if you have an interest in learning about the pit falls of furniture making then make another table from scratch and do better joins and seal it up, time will show that I am correct, and about those tables that are not sealed up underneath, they will all be cupped and show signs of movement, through the years then most persons who have run any business have taken steps to save time and thereby make more money and any question that is hard to answer can be answered in some soothing way, Like "no we don't polish timber table tops on the under side as that allows the wood to move naturally as the weather changes, wood is a living this after all"!!! Well wood that has been cut down is dead and if it is not properly sealed then it will move around as the seasons pass and anything made out of wood that is not properly sealed will twist and turn, it is why those old drawers will not open anymore. If you want to know the rest of my name then look for me on the lists of Australian Cabinetmaking Apprentices of the year. NGM

Last edited by neville9999; 05-06-2013 at 04:41 AM.
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post #9 of 9 (permalink) Old 05-06-2013, 05:52 AM Thread Starter
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Thanx, Neville. About the wood being seasoned, these boards came from the floor of a horse barn (about 50 yrs old). They were straight and true when assembled.
YES, I should have sealed the underside. The glue was standard yellow glue. Only 2 of the 6 joints show any seperation and only at the first 4-5 inches from the edge. Glue starved? Probably, it was one of my first attempts with this wood. Maybe it was softer/more absorbent than I realized.
However, lessons learned. Thanks for the advice. That's why I come to this Forum.
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