I really need help...we are seeing glue line creeping in some of our dining room table tops. we can't figure out what is causing this?? it's not always on every joint sometimes only a few. they always appear after top coating. we find if re scuff it and re lacquer it they stay down but it is so frustrating. Please help!!!
This is a common problem and a common misconception. The problem is the moisture content of your stock and the amount of time you allow from glue up to planing. What you're seeing is the wood shrinking around the cured glue line. You need to allow your wood to reach equilibrium moisture with its environment. Also, be sure to check the MC of your wood. It should be around 8-10%. Dr. Wengert has written several responses about this problem in the forum.
i have heard about the moisture content issue so i have been leaving panels clamped overnight wherever possible and a minimum of 4 hours to try to combat that. We are using Dural white glue but have seen the issue with others and the old yellow Dural as well. All of our lumber is from standard hardwood suppliers so i assume it is kiln dried to proper moisture content but maybe i should not assume. What is the proper amount of time lumber should sit in my shop for before milling and glue up? Most of our lumber is coming from the west coast by the ocean and we are in the province next door in Alberta so maybe this is causing the issue to be worse than normal? We usually let it sit for a few days wherever possible but we are a production shop and can't always do that...do i need to be leaving it sit for a week or more? how long after glue up to planning?
Using any type of water based glue you need to give the joint ample time to be able to rid the joint of the extra moisture that it has gained because of the glue.
This means a wait time of about 3 days. Ya, you heard me - days.
I've had this problem on door panels. So now what I do is glue up, plane to thickness after it's dry which is usually a few hours. Sand with my rough grit and then let them sit for a few days. Then sand with my final grit after that.
If you can't wait that long, use a glue/epoxy that is waterless.
I have seen some white glue joints that remain plastic(maybe this word will not offend the "creep" police) forever.
You could wait 3 days or 3 months and the glue will continue to move out of the joint after repeated sandings. It is because it is a soft drying glue.
Stay away from white glue.
Also while I'm at it. White glue is different from yellow glue. It is not simply a different color by a different brand as some people on WW seem to believe.
Franklin makes Titebond. #1 It drys rock hard and is easy to sand.
Franklin also makes a white glue. It is gummy and clogs sandpaper forever. It is known to remain plastic(creep move or whatever you want to call it).
Leo is correct with his recommendations for all glues. However, in my experience it may not make a difference if you are using a soft setting white glue.
You might want to invest in a moisture meter to check your wood when it comes in. Depending on how you store it it could take a long time for it to reach equilibrium with your area.
Regarding the difference between white and yellow glue; there are certainly differences between formulations of PVA glue. Some are softer than others. This is not, however, a function of the color. There are plenty of softer yellow glues out there and plenty of harder white glues. There are glues such as epoxy and polyurethane that don't contain moisture. They tend to be very expensive and more difficult to work with. If you allow your stock to reach the appropriate MC and allow it to rest after gluing before you machine you will likely do away with your raised glue line issues.
The amount of squeeze out and what you do with it will also effect this. I wait about 10 minutes and cut off the squeeze out with a chisel. If you get big squeeze out the glue inside the joint takes longer to cure out. Titebond I rock hard? Let a string of it dry on a piece of glass. Take it off and warm it with a heat gun. It droops like a wet noodle. Epoxy or resorcinol gets rock hard. Titebond I will always give a little, especially with heat!
Thank you everyone for your responses. Leo the 3 day thing will be difficult but thats how we have to deal with maple when we use it now so i guess we will have to plan production differently. Adam the white glue thing is interesting. We used Dural yellow for years and years and were convinced by a supplier to switch to white about a year ago. I have been concerned that it always seems to remain "rubbery" or pliable but i thought maybe this would help the panels expand and contract easier with less chance of cracking. Guess I was wrong! I will be switching back to yellow for sure. And Jeff the moisture meter is something i will have to look at getting I think. This never seemed to be as much of an issue when we were using local suppliers but since we switched to a west coast supplier we have been seeing it more and more. Thank you all again and will take you up on all the advice!
1. There are a number of phenomena that get described as "creep" People seem to like arguing over which qualify for use of this term. The the wood science folks enter into the discussion sporting a lab coat and PHD, however their opinions and text book knowledge are not always consistent with the way things really work.
Alot of guys who talk about this don't actually build nice things in a shop so there is a lot of really dumb info out there.
The bottom line is that "creep" can be related to the plasticity of the adhesive, or moisture introduced into the wood. From experience I have encountered and resolved problems related to both. This brings us to a couple solutions.
2. As others have pointed out it is wise to wait as long as possible after gluing up panels before final sanding. In my shop production tabletops, or door panels might get several days. A complicated lamination such a a butcher block countertop may be allowed several weeks. Quality work and furniture get several weeks.
2. Avoid using exterior PVA formulations like tightbond 2/3, unless you truly need the water resistance. For most interior woodwork they are not necessary.
I see a lot of people who are new to woodwork go for the exterior formulations
(especially tight bond 3) as the marketing buzz ("ultimate wood glue slogan") etc..." leads them to believe that it is superior.
Tightbond 1 dries rock hard in comparison.
If you want to see this for yourself, take a bottle of tightbond 1, and 3 and compare the hardness of the dried glue in the cap.
You can also use a more ridged adhesive, however this is often not practical as type 1 PVA's such as tightbond 1 are quite user friendly, and cleanup is easy.
I agree with the previous points made, but the cut of the wood can make a difference as well. That is the orientation of the rings at the glue line. With flat sawn lumber
it's possible to have vertical grain next to horizontal grain, which are going to expand/contract at different rates. Might explain why some joints move more than others.
I agree with Jeff...the color of the adhesive is not a factor.
You can also get creep from the heat applied subsequent to gluing the panels, even if you wait three days. (The failure to wait three days will give a sunken joint...a depression at many joints.) This is a good practice, but I doubt that it is the cure for your problem.
However, from your comments it sounds like you may have a raised joint; that is why you can "scuff it and then it stays down." This raised joint is caused by the heat softening the adhesive and then the pressure on the joint (all joints are under pressure) causing the soft adhesive to squeeze out. (Creep is usually referring to a long term movement, so creep may not be the best descriptive term.) So, do you use heat at the time of finishing to cure the finish? Or perhaps you use a sander or polisher that creates heat. The gloss of the finish makes such bumps, that cannot be seen in the rough, obvious.
The cure is to change to a white or yellow adhesive that is less sensitive to heat...when it cures, a chemical reaction occurs that is not reversible. In this respect, you can try TB II. You might also consider a top quality (not the cheap ones) PUR adhesive, but it is more expensive. Perhaps Jeff can give you a specific adhesive number.
This is the voice of experience speaking, as I have worked closely with this issue with others.
well I am a little confused as people are having different experiences with the Tightbond glues and which is best. We generally only use TB 3 when using exotics. Partly because we can only seem to find it retail and our suppliers carry Dural industrial glues. We are in Canada so I have never heard of Franklin? Dural has been used by many of us for years and I have only had problems since switching to their white. Gene i am not using heat to cure the lacquer but my belt sanders sure create heat. We are building higher end furniture and do mostly custom dining room tables so we do alot of belt sanding. I'm not sure how to source a glue that is less sensitive to heat as none of the labels talk about that kind of resistance. So you are recommending TB 2 for the heat issue? And Frank you are recommending TB 1 for the same reason? And Gene how do I avoid the heat issue? Once it has been heated does it cause the issue to happen again and again even if i let the piece sit for several hours before finishing? should I let it sit overnight and then lightly hand sand before staining and finishing?
Thought I'd weigh in on this from a desert location where my average humidity is in the single digits. I'm a small shop but have been using Gorilla Glue for glue ups and door panels and have never had a problem. Not sure how it would work out in a production shop but for me, it's the best way.
You're right Gene, should have mentioned that I spray one edge with water prior to glue up. Another thing I've found with the Gorilla Glue is that clean up is a breeze. I use a piece of UHMW plastic between the clamp and the wood and everything that foams out scraps, planes, or sands off without leaving any visible residue. I rarely stain so no experience there, tend to use oil, shellac, or other clear finishes only.
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