How To Repair Cracked Veneer Table Top

Introduction: Veneering a Table Top

Words and photos: Darren Oates

Once made, the veneered top of the table shown above is simply screwed-on. For a screwed on top to resist wood movement, a panel veneered over a substrate is a suitable choice.This top has camphor laurel veneered over an MDF substrate with solid Mackay cedar edging. The only problem was, the camphor laurel veneer had been sliced over 40 years ago and was very dry, brittle and, as you can see below, quite buckled. If I had pressed the veneer in this condition it would have cracked in several places and be ruined.

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Step 1: Flattening the Veneer Leaves

To flatten the veneer it had to be 'rejuvenated'. I did this by re-introducing moisture into the wood with a mixture of water, glycerin and methylated spirits. The exact ratio I used was 880ml of water with 60ml each of glycerin and methylated spirits. This made up a litre of solution, enough to rejuvenate about 20 pieces of veneer the size of my 600 x 300mm. Spray the solution onto the veneer until it is soaked. Let it sit for about an hour so the solution can permeate right through.

After an hour clamp the wet veneer under heavy pressure. Above you can see the jig I made up specifically for this task. I used two large pieces of bakelite and a steel frame with 12 large bolts, but you could easily make up the same thing with two sheets of melamine and a whole heap of G-clamps. Below you can see how the veneer looked much flatter after two hours in the press.

Step 2: Drying the Veneer

The veneer is not ready to be used yet though. It needs to dry before it can be glued to a substrate. The way to do this is to sandwich the veneer between layers of corrugated cardboard and paper towel. The cardboard allows air to pass around the veneer as it dries while the paper towel helps drain the moisture. Each piece of veneer was again pressed with the following order of layers: cardboard, paper towel, veneer, paper towel, cardboard. Once the veneers are stacked clamp them very lightly together. At this stage you are only aiming to stop them from buckling when they start to lose the moisture that was put into them. Keep them in the press for at least 12 hours and then change the paper towel and cardboard and repress them for another 12 hours. You can then change back to the first lot of cardboard and paper towel which should be dry by that stage. Using this method the veneers should be dry in two to three days.

Step 3: Matching the Grain

Arrange your veneer sections to give the best grain flow. I find the easiest way to bookmatch veneers is to match one pair (see above), tape it in place, then successively match up the third and fourth pieces (see below).

Once you've decided on the best combination of pieces use a sharp pencil to mark lines where the veneer needs to be cut. The veneers are glued butted up next to each other, so the edges need to be square. For this reason you can't use a standard knife that has an angled blade, instead you'll need to use a marking knife which has a flat side. I made a pair of marking knives from an old Stanley plane blade by cutting it in half lengthways and regrinding the blade. This gave me a left and right handed set.

Step 4: Stitching the Veneers

Use masking tape to fix the veneers into position. You can glue the veneers to a substrate with the tape on but after they have been glued and pressed the tape can be hard to remove and there is also a risk that some of the veneer will come off with the tape when you remove it. To overcome this I stitch the veneers together with yellow glue and then remove the tape when the glue has set before I press the veneers onto the substrate

Use the same roller you used for the laminating, just run a light bead along the veneer edge. When you have done this lay the sheets flat again and tape together on the opposite side to the one you already have taped, pulling the edges of the veneer together. As the veneers are dry they will want to revert back to their original buckled form, so to prevent this place a piece of MDF on top of the veneers and keep this on until they are ready to go into the press. After an hour the tape can be removed from both sides and the veneers are ready for pressing.

Step 5: Vacuum Pressing to a Substrate

After a few failures with PVA I now only use two-part epoxy for gluing veneers. I've had great success with Techniglue which is used two parts resin to one part hardener.

Make three equal sized-blobs to ensure you get the right mixture. Apply a very thin layer to both the substrate and the veneer. As this is not a water-based product the veneer will not swell. Make sure there are no blobs of glue on either the substrate or the veneer, as the glue will seep through the veneer making it hard to clean up when dry—or even worse make a bubble under the veneer. If the latter happens you'll end up sanding through the veneer. I use marine ply for my substrates as I find it to be very stable and very rigid.

I made my two-stage vacuum press set-up for a few hundred dollars and use this for all my vacuum tasks. If you don't have access to a vacuum press you can press the veneer onto the substrate between two thick pieces of MDF, but you will need a lot of clamps.

To protect the corners I put a piece of leather on each. If you don't do this the corners will be rounded under the vacuum pressure—worse still if the corner is sharp it can puncture the vacuum bag. I leave the veneer in the bag for eight hours. When this has been done you'll need to veneer the other side to prevent the substrate from cupping.

Step 6: Adding a Solid Edge

When the board comes out of the press I clean up the edges on the panel saw. The panel after I did this is shown above.To continue the theme of the timber used on the base I glued a 50mm edging of Mackay cedar onto the panel. I don't generally mitre the corners when I do this type of edging because I don't think it suits my furniture. After machining the stock for the edging I glued the short sides on first, then the long ones.

After cleaning up the edges I went over the whole top with a power sander before applying six coats of lacquer.

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