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07-28-2011 07:12 PM
Like CHHoliday who posted a couple of weeks or so ago, I also have a severe problem with that issue. I work in a basement shop which has pretty high humidity. But I always let projects dry 1 week before final sanding. I, for the life of me, could not figure out what I was doing wrong. Now I know, glue issue. My question is this, does the hide glue in a bottle solve the problem? Or real hide glue only? Or neither? What IS my best (glue)solution for edge gluing slabs(alot of my projects)? My work looks amatuerish when these flaws pop up after a couple of months, not what one wants for ones reputation. Thanks!
07-28-2011 09:32 PM
If this si something that just started to happen, I'd make sure all joint surfaces are flat, and square.
Clamping pressure and glue amount can play the trick too.
Are you using any type of alignments, ie; biscuits, T&G, etc?
What is the moisture content of the wood at the time of gluing?
How humid is in the basement?
When the project is done, where does it go to? Home? What conditions are there?
Bottom line is, the joints shouldn't pop if done right.
07-29-2011 07:09 AM
I would not think humid conditions are playing a huge role in this since most garage shop don't have a/c and it's humid outside. How much glue are you using on the joint, If you clamp it and don't get alot of squeze out there might not be enough glue. Maybe try experimenting with scrap trying different processes to see if anything changes.
07-29-2011 07:52 AM
I didn't see the earlier post to which you referred....but are you talking about glue creep? If so, that's fairly common with PVA. You can use urea formaldehyde (the plastic resin glue) which won't creep, and I don't believe hide glue will either though it comes with a whole different set of things to deal with. I have been using the UF glue on all my table tops exclusively since I learned of glue creep, but I still use PVA pretty much anywhere else. If I misunderstood your problem I apologize for this goobledy-**bleep**.
07-29-2011 07:55 AM
What you are dealing with is a form of "adhesive creep". Here is a discussion that may be helpful.
Creep has been known about for many years, perhaps even centuries. It's nothing new and has already been defined precisely, so no need to reinvent the wheel here. PVA is the classic and renowned creeper.
The tendency of the glue to ooze out of joints is one form of creep. A classic example is in a slab edge to edge glueup, such as a table top. When ambient humidity rises the timber and the the glue swell. When the ambient humidity goes down the timber shrinks again, and so does the glue, but the glue doesn't all shrink back into its original place resulting in a line of pimples disfiguring the finish. Actually, under sustained high humidity that the glue keeps on absorbing moisture and creeps out of the joint without the need for the timber to shrink. The symptoms can also be seen sometimes at the shoulder line of other joints such as mortise and tenons.
Another cause that I've witnessed several times is to make a solid timber slab with edge joints in a fairly humid workshop without climate control using PVA as described before. Then right away get to planing and preparing the surface ready for polishing with scrapers, sanding, etc.. Right after that apply the finish, whether it be varnish, pre-cat, or another finish, and take the piece into a drier house, either heated or air conditioned. Three to five days later the rows of pimples will be apparent as the timber shrinks.
07-29-2011 12:09 PM
All surfaces are flat. I have a 22' sander and they come out great. Temp- winter 64 deg f, humidity @80% humidity. Summer @70 deg and 70% humidity. I use biscuits for alignment, and from building the projects, the biscuits aren't the cause here, on a different project with no biscuits, still have lift. Plenty of clamp pressure and squeeze out. Wood usually sits in the shop for at least 2 months before use. When done, most go upstairs to my house, but many are to paying customers. Also many projects, where this isn't an issue, things still look great. Doing these glue ups for a long time, my process doesn't vary, just the results. Some times on maple. Some times on exotics. Some times doesn't happen.
07-29-2011 12:21 PM
I read that from the post a couple of weeks ago, Howie. That was when I realized I'm NOT crazy, that it really DOES happen. I just wasn't clear as to my best solution on slab edge gluing. Fred suggests urea fl. glue(plastic resin). I'm going to the store in the morning to buy some. Thanks everyone!!
07-29-2011 12:28 PM
Just remember that stuff: 1.) has a shelf life and 2.) isn't a big seller. I saw some containers of it in a local hardware that 1/4" of dust on top, and passed on buying it. Point being, it should be reasonably fresh and needs to be stored in a cool, dry place between uses.