With the veneer lay-ups (the completed, taped veneer leaves) finished, it naturally follows that somehow you’ve got to glue them down to something. For centuries, the only way to stick them to the substrate was by using animal or hide glue, still sold today in the form of Pearl Glue. Using this type of glue is not a particularly difficult process, but does require a certain amount of practice to get right as it needs to be dispensed when hot from a special, double walled, cast iron pot. The liquid glue is kept at just the right temperature by very hot water between the outer and inner shells of the pot.
Many would see it as old fashioned, which undoubtedly it is, but it does have one redeeming feature and that is the process is reversible. The application of heat or steam will soften the glue, even in an antique centuries old, which makes it an ideal medium for the furniture restorer. The latter half of the 20th century saw the development of a whole range of industrially produced synthetic adhesives, many of which are in common, everyday usage; they are also suitable for laying veneer. The big issue though, is that many of these glues are permanent and can’t be reversed, which is probably going to cause a not inconsiderable headache for a 24th century restorer attempting to rejuvenate a damaged piece made in the 21st century!
I use Titebond III for veneering, but almost any of the water soluble PVA type adhesives can be used, provided that it’s water resistant, as I’ll explain later. It can be applied with a toothed or notched applicator, but a more consistent flow of glue can be obtained using a small foam paint roller, obtained for a few pence from your local DIY store. One useful technique with thicker bandsawn veneers is to open the leaves like a book and apply glue to the joint edges.
All of these PVA adhesives are water based which may cause problems when it hits thin 0.6mm commercial veneer as it’s liable to curl. If this is going to be troublesome, then a resin or epoxy glue should be used. I’ve recently tried the West System and found it excellent, but it’s critical that the instructions for use are adhered to strictly. This problem doesn’t occur quite so much when much thicker bandsawn veneer is used.
Assuming that any lippings (where required) have been stuck on, the glue can then be applied to the substrate and the veneer laid on top. Some form of clamping pressure then needs to be applied. This can be achieved in a number of ways depending on the facilities available in the workshop.
If the workpiece area is quite small, it can be placed between two flat boards and G or F clamps can be used to apply pressure. As can be seen from the picture, deep throat clamps will be needed to reach the middle of the boards.
Larger areas present a bigger problem and require a different strategy. Professional workshops where a lot of veneering takes place will probably have a very expensive, heated, hydraulic Platen Press, which will usually handle an 8×4 sheet. The smaller establishment or even a home workshop might use a vacuum bag, where atmospheric pressure at 14.7lb/sq inch equates to nearly one ton per square foot on the work!
Commercial veneer is a smooth, uniform thickness, so both sides of the job can be veneered at the same time. Bandsawn veneer may not be quite so regular so it’s advisable to only glue one side at a time (which should be uppermost) in the vacuum press. This allows the plastic bag to pull down evenly over the whole surface of the veneer.
Once the glue has been applied it can be placed inside the bag on some sheets of waste paper to prevent any glue spillage from adhering to the baseboard. It’s a good idea to wax it as well.
Once it’s inside, I then cover it with more paper in the event of a bleed-through, where too much glue may have been used which will find its way through the pores of the veneer when it’s under pressure. The paper prevents this glue, should a bleed-through happen, from sticking to the inside of the bag.
With everything secure, the bag can be closed and the vacuum created inside. The bag will pull down rigidly over the work and the outline will be seen clearly under the plastic. The vacuum obtained is easily checked on the gauge and, as can be seen, is quite considerable.
Under normal circumstances, I usually allow around two or three hours in the bag, but the whole process can be speeded up if some local heat is used to warm the workpiece. An electric blanket covered with an old sleeping bag is quite handy and after an hour, the job underneath is a bit toasty!
Once the glue has set and the workpiece has been removed from the bag, the easiest way to remove the veneer tape is to wet it with a nylon pan scourer. After a few minutes it will simply peel away, however if the glue used is NOT waterproof, the water will lift the veneer as well…as I found out to my cost.
When everything has dried off, both the panels can be finished and, once completed, it’s quite difficult to see where the veneer join is. If it has been done correctly it will be invisible; it can be seen on the oak panel as a slightly different colour (two random pieces were used) and the join in the teak can be seen as an abrupt line across the grain figure.