Solve this glue up puzzle...

[Eric DeSilva]

I made a few end grain cherry cutting boards for Christmas presents. Several 1.5" thick, several 2.5" thick. On the thicker ones, after finishing, the glue lines magically emerged proud of the surface--like tiny ridges. The boards were sort of a subway pattern with blocks about 1.25" thick, 4" long, arranged in a 4/4/4 or 2/4/4/2 pattern, alternating. I flattened them post glue-up using my open frame sander w/80 grit, then went 80 grit -> 120 -> 220 with a ROS. Sanded, they were like glass on top. Then I applied (liberally) several coats of food-safe mineral oil, allowing it to soak in.

Did this a couple days ago and set 'em on end to let them suntan a bit in the window. When I ran my finger across the thick ones yesterday, there were the tiniest ridges where the glue lines were. Made no sense to me. I would have though, if anything, absorbing oil would have made the wood expand. Any ideas? It was an easy fix, I'm just curious about what actually happened.

[Philip Rodriquez]

Wood moves... :eek:

I've made a bunch of these. Assuming the moisture content was okay and you gave the boards enough time to acclimate to your shop... I'll guess that it was the moisture from the TBIII. How long did you let the thicker boards rest after the last glue-up?

[Eric DeSilva]

Wood moves... :eek:

I should probably clarify, I don't think this is the result of the wood slipping and the joint going out of square--I think the ridge I'm feeling is hardened glue forced out of the joint, or the wood shrinking around the glue. Probably the former. I've done these things as time has permitted over the past couple weeks. The first glue up (to make long 4/4/4s and 2/4/4/2s) was three weeks ago, then those got flattened, sawed into 2.5" strips, and the second glue up was done maybe two weeks ago. For both glue ups, the wood sat in clamps overnight, and it was probably a couple days before I started flattening. It was probably several more days before I started applying mineral oil.

The wood itself had been sitting in my shop for over a year. It is a finished (heated/cooled) basement, so there is very little humidity flux.

I just can't figure it out. The ridges appear on both on the up/down and left right glue lines.

[Philip Rodriquez]

The result is simply a result of humidity changes within the wood. The bigger the block, the greater the movement. If the wood sat for a year, I still suspect the water from the glue.

Another big factor is the direction of the growth rings. You will get a lot more movement if they are all moving in the same direction. To minimize this, you can prep your stock so the growth rings alternate.

If the ridges get too bad, resurface it in a few weeks.

[Eric DeSilva]

We're talking about an end grain cutting board. You really think it is shrinkage in length? Over 2.5"?

[Peter Quinn]

One piece moves left, one moves right, another moves X, the next piece moves Y. The whole thing is a giant push-me pull you. I doubt you had much movement in length over 2.5", and the moisture from the glue should have worked its way out over 2 weeks. Which glue? I don't tend to think of cherry as one of the most stable species. Pretty, yes, but not stable. What do I think happened? Wood moved.

I was a chef for a number of years before becoming a wood worker, and I can tell you that end grain butcher blocks in use in real professional kitchens do not tend to stay perfectly flat, nor is that a particularly important factor in their performance. "Flat" is really only important in show pieces. Spend a few years butchering meat on one on a daily basis and it will take on a lovely soft patina, and you will scarcely remember those ridges. Christmas presents you say? I guess most people would not appreciate a two year old, smells vaguely like meat, blood stained, salt bleached, battle scared butchers block as a gift?

[John Coloccia]

There's just something I'm not understanding. If the wood is all glued to itself, how is a glue line making little ridges? I could see maybe possibly getting little bumps, and maybe that's what you're describing, but I'm reading it as getting sharp little ridges right at the glue line. Is this true?

I've never made an end-grain cutting board so maybe I'm just inexperienced, but I'm just having a hard time understanding how the wood could make such a sharp ridge unless it's coming unglued. Does that make sense?

Now what I HAVE seen is someone try to sand down a glue-up, and the sandpaper leaving the glue lines proud of the surface because they're rock hard and don't sand easily. When you run your hand over the surface there's enough dust to make it seem smooth. Then they wipe on some oil, walk away, and when he comes back the glue lines appears, but actually it was just the act of cleaning away the dust by wiping with oil that made it apparent.

Anyhow, I'm just rambling. I'm really interested what's going on too because a cutting board is high on my list of things to make this winter (my old store bought one is finally starting to split after many years of service).

[Chris Ricker]

I think what you are experiencing is called "glue creep"
Don't worry too much, it's common and easily repaired. just sand with your last grit sandpaper and re-apply the mineral oil. it happens to me nearly every time I do an end grain.
you'll have to google "glue creep" for a scientific explanation if you would like, but it really is nothing to worry about.
In fact I have 4 boards in the shop that were finished(done) about 3 weeks ago, they have it and should pose no problem after a knock down sand and re-oil.

[Howard Acheson]

I bet you used a PVA adhesive like Titebond. That is a very characteristic result of moisture and heat changes. Here is a treatise the is the best discussion I have seen of the issue.

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 my anecdotal observations are 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 polish, 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.

Somewhat related to this is using an aid for edge glue alignment, such as biscuits with PVA. These jobs need time to settle. If you are in too much of a hurry and prepare for and polish it all as soon as you get the piece out of the clamps, the chances are you'll see a row of rugby ball shaped depressions telegraphing the position of every biscuit a couple or three weeks later, although I've seen them appear as much as a year, or more, later. The moisture in the glue swells the wood either side of the biscuit, and it takes a week or two for this moisture to work its way out of the joint properly. My advice then is to not rush into the preparing for and polishing stages after this type of glueup, particularly table tops and the like which show off every flaw. I don't use PVA for this specific kind of glueup at all anymore here in hot, humid Houston. I tend to reach for the hide glue nowadays, either out of the pot, or the liquid stuff.

[Kyle Iwamoto]

Hmmm.... I guess you shouldn't worry about it. It happened to me, and I was also interested in what the cause is/was. I just got my cabinet scraper and got rid of it. It creeped a couple times, and hasn't been a problem for the last year. And we use the cutting board constantly.

This is such an awesome board. So many knowlegdeable folk! TYVM for all the replies.