Sunday, 3 May 2020

Building a 13 Course Lute, Start to Finish, 17: Finishing out, Prep for Varnish

Hi again, and welcome back to the workshop. How are you doing during the Great Hush of 2020?  I'm still here making my lutes; and I hope you're keeping well, wherever you are.

Let's get to it. I've got a bunch of things to do to prep this 13 course lute-in-progress for varnish, including some preparatory seal- and ground-coats to the body and belly. First, however, I need to finish out the instrument.

But what does 'finishing out' really mean? To me, it means going over the entire lute, very methodically, to give it a complete and final physical shape. I've got a checklist of tasks that I go through from top to bottom, which bring the lute to a certain point of completion. This checklist ensures two things: first, that I don't miss out on any details in shaping the lute; and second, that the process doesn't go on forever. I have a task; I do it; I cross it off the list; I go on to the next. Magically, it seems, the lute gets done.

A small item to begin. Remember back in episode 3 of this series, when I bent and glued the ebony veneer onto the neck core? I used two pins to locate the veneer when I glued it, one near the nut end, and one in the middle of the neck. Those two holes are still in the veneer. The one at the nut end will eventually be obliterated by the peg box rebate, so I don't need to worry about that one. The one in the middle, however, needs to be filled.

With a jeweller's pin vise, I drill the hole to a slightly larger diameter.

Then, with files and a scraper, I make a dowel from a scrap of ebony that fits the hole. I glue it in, and when the glue's dry, I nip it off, and file it flush.
Next up: rectify the body-neck joint. My result was pretty good when I veneered the neck and glued it to the body, but you can see  here a small area where the match isn't quite exact. I'll make it exact with files; then I'll go on with the files to give a good shape to the back, starting with the top block area adjacent to the body-neck joint.

Then I move on to the rest of the back, and give the whole thing a final shape. This part of the process probably takes the longest of all the steps I'm describing in this post. I work with files and some small, curved scrapers, using strong side lighting to see how tight the rib lines are. You can see in about the centre of this photo that the rib above sits a little higher than the one below; I will file and scrape in that area until the facets of the ribs, and the line between them, are rectified. I then do the same thing with all other problem areas, all over the back of the lute.

I was going to say "I will file and scrape in that area until the facets of the ribs, and line between them, are perfect," but that's not exactly correct. Perfection is an ideal state, and therefore unattainable; I merely work until I have achieved a satisfactory result. I look at the lute in all sorts of different lighting situations; I set it aside and do some other work for a while, so that I may come back to it with fresh eyes. Each time I come back to it, I find a new spot to work on. Until I don't!--and then it's time to check this task off the list, and move onto the next one.

Here's a good shot showing how I brace the lute when I'm scraping the back--between my knees and the well-padded edge of the workbench.
I have made a few scrapers for myself with different curvatures. I  match the scraper I use to the width and curvature of the rib I'm working with.
From there, I move onto finishing out the neck. I mask off the top of the body (don't want ebony dust to get into the freshly-scraped back), and work with a series of files.
When I get a good overall look with my finest file, I move onto burnishing with shave grass. In this photo, you can see, at bottom, a segment of shave grass, and in the middle, a segment of shave grass that I've slit open, flattened, and backed with a piece of masking tape. I can then use this flattened piece with a cork sanding block (seen at the top), to get a very nice burnished surface on the neck veneer. 
Just a word about the scraping and burnishing process. You may have noticed that I have not mentioned the word "sandpaper" here, and that is because in finishing out this lute (and the other two in this group), I resolved not to use that material. In the past, I have finished out the veneers and backs of my lutes with a series of sandpapers of ever-finer grits, but I decided with this group--and, I hope, from now on in my lute making practice as a whole--not to use it to finish out necks and backs. (I have never used sandpaper on the bellies of my lutes.) I decided to do this for two reasons. First, over the years I have developed sensitivities to wood dust, especially ebony and rosewood. Sandpaper creates a lot of dust, so by eliminating it from the finishing-out routine, I hope to significantly reduce my allergic/asthmatic sensitivities. Second, I have long believed that while sandpaper offers a certain convenience in finishing out, it also tends to give an instrument a kind of 'rounded over' look overall, diminishing the crispness in texture that I would prefer to see in surfaces and edges. I'm not talking about creating sharp edges here; quite the contrary, in the next few photos I'll describe how I methodically eliminate any sharp edges that might interfere with the comfortable playing of this instrument. In this context, I am referring only to the visual aspect of the lute, how it catches the light, and the eye of the beholder, to create a bold visual interest.

So for the back and neck veneers of this lute, the finishing out process is as follows: file, scrape, and burnish with shave grass. That's it.

The biggest and sharpest edge on the lute, at the moment, is the edge of the fingerboard. I want to ease the fingerboard edges and create a radius in an orderly way not only so that it's comfortable to handle, but also so that gut frets will tie more easily and lie flat against the fingerboard. (A too-sharp fingerboard edge will make the frets sit up off the fingerboard, which will interfere with the sound of the first one or two courses.)

I use a file to chamfer a 45˚ surface about 1-2mm wide on the edge of the fingerboard. Then I use the file to relieve these two new edges I've created, until the fingerboard edge is smooth and well-rounded.

I then carry on to the belly edge-binding. Again, I use a fine file to make a 45˚ chamfer that goes about halfway down through the thickness of the binding.

Then I round those two newly-created edges over, until I've got a very friendly-feeling edge. Remember, the bottom of this belly edge will be resting on the player's leg, and the player's arm will rest against the upper bottom corner of the belly. The "softness" of these edges is, in my opinion, a crucial part of making this a very playable instrument.
Where these two chamfered edges meet, I ease off the rounding over, and try to match them simply and crisply.

Finishing out the belly is fairly straightforward: I scrape it carefully with a small, sharp, flat scraper along the grain, in whatever direction works best...

And then I burnish with shave grass. This stuff works best on the spruce if it's rubbed across, but held slightly askew, the grain.
At the end of the day, I wet the belly with distilled water, to raise the grain. I let this dry overnight, and next morning scrape and burnish the belly one more time.

I then seal the rose with a brushed-on coat of Tried and True oil. Then I hang the lute in the UV light box for a couple of days, to let it tan up a bit, before I begin applying ground coats before varnishing.
Two days later....

I bring the group of lutes out of the light box, and make ready to apply the first seal coats to the belly and back. The first thing I need to do is mask of the neck and fingerboard carefully.

Then I mix up my sealer: a dilute mixture of casein glue. I use about a tablespoon of low-fat dry curd cottage cheese, a small amount of artist's slaked lime, and distilled water.

Stirring the slaked lime to prepare for use. 

Dry curd cottage cheese.

I grind the cottage cheese first to minimize lumps, then mix in the slaked lime. Finally, I dilute with distilled water.

Then I begin padding it on the front of the lute with a soft cotton cloth, starting out above the bridge, and working around the rose to the top of the belly, and around and down the belly below the bridge.

Around the bridge, I apply the size with a small brush. I'm a little sparing in my application of the size around this area.

I keep applying the size for a few minutes until I have a nice, even coat. Then I take a fresh cotton cloth and wipe the belly down, along the grain, to remove any excess specks of cheese that may not have been ground down well in the mortar.
Next step is to apply the casein size to the back of the lute. This time I apply it with a wide, soft brush, and brush along the length of the rib. (Notice also in this picture that I have swapped out my green cloth bench pad for a large piece of card stock. During this stage, and during varnishing, I handle the lute by holding onto the neck with my left hand, and allowing the edge of the lute to rest on the card.)

At this time I also apply my size/seal coat to a sample of the same material as the back of the lute. From now on, whatever I apply to the lute, I apply to this varnish sample.

When I've applied an even coat, I wipe down the back with a fresh cloth to remove any large bits of unmixed material. 
And--back in the light box for another couple of days, to let the seal coat harden up.

You might be asking: why apply a seal coat at all? Well, there are a number of reasons. First, a coat of dilute glue such as this will consolidate the wood fibres of the belly and back, and create a flatter surface on which to apply layers of varnish. Second, the seal coat will help with adhesion of varnish coats. And third, and most important, the seal coat will actually create a barrier between the wood and the varnish coat, which in the case of rosewood (which this back is made from) and yew wood (which another lute in this batch is made from), is essential. Both rosewood and yew have oils in them that, unless the woods are sealed off somehow, will interfere with the bonding and curing of varnish. For years I used a coat of shellac as a sealer for rosewood and yew, but that stuff is problematic for a couple of reasons (for one, it's a bit anachronistic to be using in an 'early' instrument such as this.) Grant Tomlinson introduced me to casein, and I've used it for a few years now. It works well, and it is easy to apply.

Okay--one more coat, this time a ground coat, the purposes of which are to penetrate and strengthen the wood of the belly and back, to give added depth to the finish, and to promote adhesion of the coming varnish layers. The three ingredients: marienglas, Tried and True oil, and my own oil varnish.

The three ingredients are measured out on a glass plate.

I mix them together with a muller.

I dilute the mixture with spirit of gum turpentine...

And then apply it in a thin layer to the belly with a cotton pad, in much the same way that I applied the casein size.

I apply this coat to the bridge...

As well as to the rose (I use a very dry brush in doing so.)

As a final touch, to even out the coat, I brush gently but quickly across the grain with a broad, soft brush. (By the way: this is the final coat of finish I put on the belly of my lutes.)
I apply a coat to the back of the lute, using a cotton pad.

I love the way the lute starts to look at this stage--I can already begin to sense the glow of the wood below just these preparatory layers. I'm quite excited to put a few coats of varnish on this lute!

There is my batch: from left to right, the 13 course in rosewood, a 7 course in yew, and an 8 course in rosewood.

Next time, I will tell you about my varnish, and I will show you how I varnish a lute back. There might even be moving pictures....

Stay well, and I'll see you next time.