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Split along the glue joint - why?1/9
The other post about splits in the shop was well timed as we just got a call about a Boos Block we installed about a year ago. It was finished with oil that the home owner swears they are maintaining. It looks dry to me but we have an appointment later in the week to see it in person.
I'm guessing humidification is to blame since this crack opened up a couple inches on Saturday and is now about 12" long. Why would it crack along the glue joint? This would indicate an improperly prepared joint, at least how I understand all of this, but isn't the glue supposed to bond stronger than the wood itself?
How would you handle this? We had to cut the original block to size so we voided the warranty from Boos. Is the homeowner to blame for not "properly" conditioning their home?
Is the only solution here to redress the joint and reglue? I would prefer to leave it in place and not bring it back to the shop.
Thanks for your help. I rarely post but really enjoy this forum.
How's the block mounted? I've seen more than one of those screwed tight to the cabinet, no oversized holes in the cabinet cleats. So when the solid wood shrinks or expands, something has to give. If you didn't have slots or oversize holes in the cabinet, it's your mistake to fix. The top has to come off and the holes opened up. Then it's a discussion between you and the homeowner. Do they want you to take the top back and rip it down the crack and reglue, or are they okay with you gluing in a small tapered ripping and then sanding and refinishing.
What the responses to the previous post doesn't address but may be the culprit is allowing for movement in the installation. Did you fix the top with slotted holes for the screws? A top could easily shrink 5/16" in dry winter conditions.
Sorry for not including our installation method - we drilled an over-sized hole and used a screw with a fender washer to allow for seasonal movement. I don't think we restricted any wood movement and would be surprised if that were the cause. We've done a few like this and this is only one we've gotten a call about.
This off the Boos site:
Kitchen Counter Tops - Wood: Care & Maintenance - Download PDF
Extremes of humidity and dryness can swell and shrink hard rock maple and/or oak enough to cause small seasonal checks to appear, usually at the ends of tops or at the end of a lamination. This possibility, though remote, is an unavoidable condition of enjoying the character and beauty of a living material. Cracks filled with a cellulose filler of the right tint become practically invisible. You can help preserve your wood table top by keeping your home humidified in the winter and by refreshing your table often with Boos ® Mystery Oil and/or Boos Block ® Board Cream.
All Butcher Block products is recommended to be oiled on all surfaces with Boos ® Mystery Oil and/or Boos Block ® Board Cream at least once every 1-2 weeks depending on the use or household conditions. This will help protect the wood from damage. With a minimum amount of care and maintenance on your Wood Table Top, you can lengthen the life of the top for many years.
We always fasten one edge hard to the cabinet. Then drill 1" long slotted holes. Fender washers and screws are fastened lightly with a screwdriver. You would have to drill a huge hole to allow for the expansion in both directions.
The idea is that you control which way it moves.
So what happened. The moisture content of the counter top went down enough for it to shrink. It had a bad glue joint. It should have cracked next to the glue joint.
This all could have been prevented by allowing the counter top to move around more.
Cracks near the ends are not unusual perhaps a screw went into the joint ?
I'm not anticipating installation to be the guilty party. I understand about screwing one side tight. I don't do this because if you have more movement than you allowed for at the other end, or if you screw isn't centered in that hole, trouble can arise.
We drilled 3/4" holes in the stretchers at the front and rear and used fender washers like Adam described. We've done a few of these and this is our first problem.
They sent me a picture this morning. It looks like there are wood fibers in the joint, so maybe not a total joint failure? I would assume with a total joint failure both sides of the joint would be clean, since the glue never would have achieved a good bond with the wood. And I'm not thinking these fibers are food/trash as this just opened up on Saturday.
When you look at the to, meter the underside in several places along the edges and in the center of the top. If you have pinless meter, measure the top surface.
Use a sling hygrometer or a digital one to check the RH in the room. Ask about humidification. Have copies of Boos info as well as Spekva (see other thread) to show to your customer. Then go away and make your determination.
I see what I would call glue fibers more than wood fibers in the open joint. At 1/16", that is a lot to fill - anticipating that it could try to close up and then cause compression set, and another crack nearby if the RH change is cyclical. I'd suggest a hard colored wax for the time being.
How do you fix anything after its been oiled?
What said to me wood fibers is a zoom in on the very bottom edge. It looks like some of these pieces jag into each other. Glue wouldn't likely do this.
So if an increase in humidity should close up the joint, would a decent approach be to do nothing now and wait for the interior humidity to normalize and then epoxy?
I'd though about bringing a humidity gauge with me, but I'm not sure what revelations it will bring if the overall temps are up and the heater isn't running all the time. This would likely show higher humidities, which would discredit my explanation for what is going on. Overall, this is a pretty crappy situation for all involved.
I took another look at the glue joint. It looks like something dissolved the glue. Like it turned to mush and the moisture change tore it apart.
What adhesive does Boos Block use on their countertops?
What has the customer been putting on it? Call Boos Block and ask them what chemical would aggressively attack their adhesive.
Perhaps the customer is at fault...
I am told they have put mineral oil on it and oiled it every month. I won't get to see it until next week sometime as my appointment got pushed back. Boos won't reveal their glue information.
One solution may be to place a draw bolt
It would be nice for Mr Jones were the glue to be found at fault, but I have seen that look before. Glue or wood or both or neither, it is open, yawning trouble coming your way.
I have to say it is heat and low humidity. This thing is open because that end is drying out and shrinking. But the bulk of the wood has not dried out as fast as the end. It was just looking for the weakest place to crack. I will bet that a heat register/wood stove/dishwasher is much closer to this end than the other. The only other cause I can offer is that one piece or the other is/was a bit higher MC than its neighbors, and as it equalized, it shrunk and opened. Hence you know where to meter.
When one looks at woodwork, one thing historically is that end grain was always coved up. Stair tread returns are a good example. Even the better flooring jobs had a perimeter that covered up the end grain in the main field of the floor. Some exterior doors had 'shoe' molding that covered the ends of the stiles, and all along the bottom rail. Butcher blocks did not have returns, but they did have the threaded rods since the glue was not reliable and compression set was a small price to pay for the use of that end grain Hard Maple.
I think threaded rods, countertop bolts and even a big a** clamp would not fix it, or fix it for long. You can fill it with colored wax as a goodwill gesture, take no blame, and ask to watch it for a year. The old guys I used to work with said that if it lasts a year - a full cycle of seasons - then it will last forever.
D - Good stuff with the draw bolt. It would be almost as much work vs. ripping, jointing and regluing. I'm leaning towards David's suggestion of wax-and-see, but I do will keep that idea in my back pocket.
David - The top has been installed for eleven months.
I also agree about low humidity and heat causing this to happen, and to happen so quickly (it was suddenly there on Saturday, when the wind chill was around zero).
However, why did it pop at the glue joint? Bad luck? Was that the weakest link in the glued up chain? Was it shrinking and was going to crack at the weakest point, and the joint happened to be it, even though it was strong enough to keep everything together when the humidity was in a more suitable range?
Where's Dr. Gene?
If you put a draw bolt under it, make sure to go out in the spring and loosen it up. If you don't, the wood cells will crush under the bolt head and the crack will open back up next winter. Put too long of a rod under it, and the top will want to bow this spring.
How big is this counter top?. If its held down only by the screws you described, it should come off in minutes.
Stuff the thing thru the table saw with a decent blade. Wash the oil off with acetone. Glue it back together with epoxy. Reinstall it.
Why did it crack on the glue joint?
It had to crack somewhere.
While the glue joint may cause you to question all the glue joints in the entire top, it may just have been in one end of one pice that did not get prepped correctly - or as well as all the rest of the joints.
Planer snipe, ripsaw angle, less glue, burnished wood surface(s), glue not allowed to 'wet out', etc. can all cause a stressed joint to fail.
You have no control over that since you did not make the top.