Balancing a Table Top

Balancing the veneers, the finishes, and the construction sequence will help keep the table flat. March 30, 2008

I am making a conference table top 44" diameter x 29" high. What would be the best material to use, besides solid: particleboard or MDF? I made one top table using particleboard, with 5-ply veneer construction, high sheen rubbed finish on top, and on the back of the top table, we used sealer and stain only. The problem after finishing was the top cupped (convex). Can anyone suggest how to avoid cupping on the top table?

Forum Responses
(Furniture Making Forum)
From contributor N:
Please clarify "5-ply veneer construction... and on the back of the top table... sealer and stain only." It sounds like you put 5 layers of veneer on particleboard, which doesn't make sense to me. When you say the back (bottom) of the table had sealer and stain only, do you mean sealer and stain on veneer or on exposed particleboard?

From contributor J:
Must be for small conferences! My kitchen table is that size. Anyway, the best material depends on what equipment you have to work with, and what you are experienced with. I'd build it out of solid unless it was some species that wasn't available or was cost prohibitive in solid.

Your table cupped because you created a moisture imbalance by not putting the same amount of finish on the underside, and I suspect you didn't veneer it either. Remember, what you do to one side of a panel, you need to do the same to the other. If you do that, your problems should be minimized.

From the original questioner:
A 5-ply veneer will have a core with the grain running north-south, a layer on either side of the core with grain running east-west and another layer on either side with grain running north-south.

What I used on my conference table:
1. Face veneer (crotch mahogany)
2. Cross band
3. Particleboard
4. Cross band
5. Back veneer (Q/cut mahogany)

On the back veneer (Q/cut mahogany), we put sap stain, smoothcoat, and high-solid sealer. On the top (crotch mahogany), we did very high sheen (gloss) rubbed finish.

Contributor J, you are correct about the moisture imbalance by not putting the same amount of finish on the underside. The problem is on the top of the table, we did high gloss rubbed finish. What finish should we do on the underside?

From contributor N:
I would use the same product as on the face, in the same number of coats. You don't have to rub it out like the top. Most of my tables are hand rubbed oil and wax. I do the same 5 or 6 applications on the underside, but I don't get as carried away wet sanding on the underside.

Why did you do all that crossbanding? Was the crotch material really wrinkly or something? Seems unnecessary to me.

From contributor P:
The finish is definitely a problem, and the veneering might be too. While you got the right balance of layers on both sides, you also have to look at the sequence they were done - you can't do one side completely and then do the other, or you will have an uneven moisture balance in the core. I don't think there is anything wrong with crossbanding under the face veneer, as particleboard can sometimes telegraph through a single layer of finish.