Good caulk for wide pine boards?

[Charley Hunsdorfer]

I just refinished a coffee table top with spar varnish. The top is made up of 3, 10" pine boards, rabbeted and overlapped where they meet.

These open joints are great collectors of dust, table salt, dust and anything that gets spilled.

My plan is to trim the joint edges (circular saw or router) to bare wood on the two opposing inside faces, put a bond breaker (string, shoelace) down at the bottom of the joint and apply a dark brown caulk of some kind, to keep liquids and debris out.

However, I do realize that the pine will come and go some and I have to choose the caulk well to avoid adhesion failure.

Any thoughts on what caulk will be fairly tough, resilient and adhere well to bare wood? I would prefer a flat finish.

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[Tom Ewell]

Maybe look into boat deck caulks/sealants.
Not sure about color selections
Check out for potential, if any, toxicity problems too.

[Jason Roehl]

Elastomeric.

Buy a real bond breaker--foam backer rod.

[Frederick Skelly]

I'm not 100% sure I'm following you. Are you going to essentially run your saw down the length of each joint, basically cutting a shallow groove?

This is not the solution you are asking about, but if you are going to cut such a groove, you might consider gluing in a narrow piece of pine instead of caulk. I suggest this because to me, caulk is unsightly on a piece as pretty as that. In addition, I think you'll get more durability out of wood than caulk in that application. (Table tops get rubbed on every time you clean them after a meal.) Another idea could be clear epoxy instead of caulk.

Good luck with whatever approach you decide on.

[lawrence dosson]

charley
I am assuming that you are allowing wood movement at your overlapping joints is this correct ?
in other words you have each board fixed at the base were as there can only be movement across there width at the seams
if that is the way your table is then you will have a hard time using any hard caulk ETC it will always want to expand and contract at your board joints
lovely table buy the way but the way we normally build table tops from solid wood is to make tight joints glued up solid no cracks at all and allow for the expansion buy the method it is attached to the base RE: figure eights- some type of slots and z clips or some thing similar

[Bill Space]

I have had good luck in a table made from a slice of a tree trunk, using 100% silicone rubber Caulking. It is a slice across the growth rings so some splits are wide and some are very narrow.

If your table were mine, I would first just try putting a dark brown colored 100% silicone caulking into the existing grooves that you want to fill. I would put blue painters tape along the edges of the grooves you want to fill, and then fill them with caulking. Then I would run my finger, or possibly a straight edge of some type, along the top surface to get a smooth bead. Finally I would remove the blue painters tape while the silicon caulking was still tacky.

Leave the table top untouched for 24 hours to be sure that the silicone cures properly and then you should be good to go.

If for some reason you do not get a satisfactory result, you have not wasted much time and can then proceed with a more time-consuming fix.

The only question is how deep those existing grooves are and whether there will be enough grip for the silicon rubber. My guess is the caulking will probably grip OK...

Bill

[Frank Drew]

I don't associate caulk with furniture making so I'd rework the table with tight fitting glue joints.

[John C Bush]

I have used marine urethane caulking/sealer/adhesive to seal between mahogany planks for hatch covers.(Old boat restoration) It is flexible, adheres well, and is sandable. IIRC we used teak oil as a finish. Haven't seen it for a few years but no mention of any downside from the freind i did it for. Comes in conventional caulking tubes and is reasonable cost.

[Charley Hunsdorfer]

Thank you all for the replies.

Yes, it is my intention to clean the wood edges of the joints buy cutting, to create a better bonding surface for the caulk. I will only enlarge the gaps as little as is necessary to accomplish that. I will try a bronze exterior silicone and cross my fingers that it will adhere well enough.

Yes, I know the boards will expand and contract. If I were to fill the spaces in solid, or rip and edge glue to make one whole, I'd be concerned about future splitting during seasonal changes. I could remove the boards and finish both sides to help reduce that possibility, overall not a bad idea, but we like the seamed look.

You will notice that a corner was at one time broken off. The original owner had tacked it back on with finish nails. I asked my wife if she wanted me to replace that board, but she said the crack added to character of the table, so I made a stronger repair with wooden dowels. I left all the nail holes (from previous repairs, trim that was removed, etc.) that show both on the surface and around the edges, taking care to soak them with both linseed oil and then varnish. There are even the remnants of old red and white paint in the crevasses, which she elected to keep.

Again, I appreciate all the input. I'll show the end result in a few days.

[Alan Schwabacher]

It sounds like the problem is not the gap, but that it's closed at the bottom. If you disassemble to clean the edges of each piece, what if you rip off the rabbet from one piece, and glue it into the rabbet of the other. This converts from shiplap to simple slightly open joints that look almost the same from on top, but if crud gets in it can fall out the bottom.

If you do choose to use a caulk, it seems likely you'd get best results by not applying it to bare wood. A finish that sticks to wood, followed by a caulk that sticks to the finish, is likely to work better.

[Frank Pratt]

I can't for the life of me understand why you would want to use caulk as a solution to the problem. Caulk & furniture just don't belong together. The result will be ugly at best. That's a beautiful old table, give it the repair it deserves.

I'd remove the top, separate the 3 boards & then lightly joint the edges. Just enough to get a good flat glue surface, yet still leave a little of the round over on the corners. Then glue it back together, carefully lining up the edges & wiping of any squeeze out. Then fasten the top back to the base in a manner that will allow for seasonal wood movement. You shouldn't even have to do any refinishing other than maybe some tinted wax.

The top will still have those visible seams (which are part of it's charm) but there will be no cracks to hold crumbs & gunk. Good luck & post pics of your results.

[Joe Jensen]

I can't for the life of me understand why you would want to use caulk as a solution to the problem. Caulk & furniture just don't belong together. The result will be ugly at best. That's a beautiful old table, give it the repair it deserves.

I'd remove the top, separate the 3 boards & then lightly joint the edges. Just enough to get a good flat glue surface, yet still leave a little of the round over on the corners. Then glue it back together, carefully lining up the edges & wiping of any squeeze out. Then fasten the top back to the base in a manner that will allow for seasonal wood movement. You shouldn't even have to do any refinishing other than maybe some tinted wax.

The top will still have those visible seams (which are part of it's charm) but there will be no cracks to hold crumbs & gunk. Good luck & post pics of your results.

Agree, this is what I'd do.

[Tom Ewell]

Perhaps the OP just likes a variation of the look
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