Marquetry: More Art than Craft
By Alan Mansfield of the Redbridge Marquetry Group, U.K.

Lesson 9: Blending Veneers

 

 

This month, let's consider how to blend one veneer into another for a smooth transition. One of the best blending techniques I know was taught to me by a very well-known veneer preparer and multiple award winner, Alan Townsend. It makes an almost invisible blend of veneers and is known as the "spears" method. I have only used this method on the UK's 1/64" thickness veneers, while using scalpel blades. It will probably work with American 1/32" thick veneers when they are saw cut, but I would make sure that the veneers are taped together first as misalignment would be very noticeable.

In the first illustration at right, I've cut a random saw-tooth edge on my picture veneer using a scalpel. Next, I place the veneer that I want to blend into my picture beneath the picture veneer, and line it up with the saw tooth edge until it presents the effect that I require. Once I'm satisfied with the look of the veneers, I cut into my new piece of veneer (the one that I'm blending in) with my scalpel blade by using the saw tooth cuts on my picture veneer as a template. This will become clearer if you look at the second illustration below.  
  I have found it's more accurate if you place your scalpel blade in an Exacto-style knife handle. (I use Swann Morton blades ground down on a diamond stone for this purpose, as it gives me much more accurate control than an E11 scalpel blade in a surgeon's scalpel handle.) The important point here is that you don't want the blade flexing about, causing a loss of accuracy. Slight gaps usually disappear with the natural swelling of veneer fibres when PVA glue is applied (this being due to the moisture content of the glue). As I mentioned in one of our previous talks, professional veneer preparers use ground down hacksaw blades held in very sturdy handles for the stability and accuracy they offer. They are also adept at sharpening these home-made implements.
You should vary your cutting line so that the joining pattern doesn't resemble a line done on a sewing machine. What I mean here is every half inch or so, move the direction of the line of spear points slightly off their predictable course so that they appear more random. If you have a look at the spear point joining line illustration at right, this will become clearer.  

Choose your Species
Some veneers lend themselves to the spear point blending method better than others. It's best to avoid veneers that crumble when cut, because they don't keep acute angles intact after you've cut them (even if you place gummed tape on the rear). You could try rubbing thinned down PVA (white) glue into such veneers to try and prevent the crumbling. However it's best to just stick with veneers where the wood fibres retain their structure when cut, without having to resort to glue and tapes.
It's also the best practice to have the grain of both veneers running in the same direction, as it is very difficult to cut spears across the grain. Some of the veneers which lend themselves well to the spear point blending techniques are aspen, castello, walnut and olive ash. Burl veneers unfortunately don't take kindly to this method of invisible joining. Burls by their very nature have random grain patterns and nearly all of them crumble to some extent if you try this method.
In one of my pictures I did actually manage to blend some pieces of poplar burl into some sycamore and rosewood by using the spear point method. I stuck veneer tape to the rear cutting areas of all the veneers that I was using, and also smeared diluted PVA glue on the cutting areas (and let it dry before cutting, of course). When I did the actual cutting I made sure that my cutting tip was perfectly honed by doing several test cuts on sheets of paper. I also used sharpened frequently on a fine grade diamond stone during the cuts, and used plenty of bee's wax to lubricate the tip of my blade. By taking my time and doing the job carefully so that the blade didn't pull, I managed to blend the veneers together without breaking off any of the spear points. It was tricky, but it was worth the effort in the end.

When you are doing the spear point blending method you may find it useful to use some form of magnifying glass - either a stand-supported model or special spectacles with strong directional lighting - in order to ensure accuracy in your spear point saw toothed cutting line. While we are on the subject of magnifiers and lighting, as these are of particular importance to many marquetarians, that will be one of the subjects that we will investigate in a little bit more depth in our next session. Until then, please do enjoy your marquetry, and happy cutting!
Cheers,
Alan


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