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Category Archives: finishing

Among the treasure trove of information and tips and tricks at Frank Ford’s website Frets.com there’s a description of how to turn a single-edge razor blade into a miniature cabinet scraper for repairs of guitar finishes. Click here to read it.
 

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I thought that this was a really clever idea and immediately ordered a box of blades to try it out. Ford says that he draws the edge of the blade across a round piece of hard steel such as a screwdriver shank to create a fine hook just as one might finish a full size cabinet scraper.

I’m not sure why, but I couldn’t make it work. Maybe it was my technique or perhaps the steel of the blade had hardened during the sharpening process but despite repeated trials all I could produce was a ragged edge that scraped less well than a blade straight from the box.

 

The solution was first to grind off the bevelled edge of the blade;

 

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then to make the blade edge straight and square on a diamond stone;

 

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and finally to turn a hook with a burnisher in the usual way.

 

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These little scrapers work extremely well if you need to remove polish or varnish and they’re easy to re-sharpen.

 

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I had intended my previous post to be the last on the V joint. But, as I’ve just completed a guitar using the one that I made for the photographs, the series can end in a rather more satisfactory way by showing how it turned out on an actual instrument.

 

 
Here’s a close-up to show any sceptics that the small extra piece of wood glued on to the male part of the V really is invisible in the finished joint – scroll down to the last couple of photographs in this post if you can’t remember what I’m talking about.

 

Continuing my experiments with smaller guitars led me back to the 19th century and the instruments made by Louis Panormo. One of his guitars, made circa 1840, is in the Edinburgh University Collection of Historic Musical Instruments and, rather helpfully, a workshop drawing is available. I had other assistance too. My friend, Peter Barton, who makes fine acoustic guitars in Addingham, West Yorkshire has a Panormo guitar in his collection, which he generously allowed me to handle and photograph. And Gary Demos has a series of photographs documenting his construction of a Panormo guitar copy on his website.

Here are some photographs of the instrument as it was being built. It isn’t, and wasn’t intended to be, a slavish copy. I felt no need, for example, to reproduce the inexplicable scarf joint at the heel end of the neck that was indicated in the drawing of the Edinburgh instrument and that you may just be able to see below in the Panormo guitar owned by Peter Barton. In the photograph, it runs more or less horizontally from where the neck joins the ribs to the back of the neck, ending around the 7th fret position. (Do tell me, if you understand why Panormo did this.)

I also felt free to to inlay spalted beech for the rosette instead of the mother of pearl set in mastic of the original.

I did however, reproduce the V-joint between the neck and headstock, although the width of the headstock itself was increased slightly to accommodate modern tuning machines. Followers of this blog might recall an earlier post about making the V-joint.


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The bridge design is more or less the same as Panormo’s, except that a slot was routed for a carbon fibre saddle to provide a little leeway for adjusting the action later on. His bridge has no saddle. Ebony bridge pins were turned to replicate the original way of fixing the strings.

Here are 3 photographs of the completed guitar. The body length is 450mm, width across lower bout 290mm and scale length 630mm.


 

You can hear Gill Robinson, who now owns the guitar, playing three short pieces if you click on the titles below.

Allegro

The rain it raineth

Caleno costure me

The guitar that I have been writing about in my last few posts is now, more or less, completed. It’s finished with French polish, which will benefit from a final burnishing in a couple of weeks time when it has got fully hard. But I couldn’t wait any longer to string it up and hear how it sounds. The back and ribs are zebrano and the soundboard is European spruce. The binding is Rio rosewood and maple, and the soundhole rosette and headstock veneer are spalted beech. I’m pleased with how it has worked out, though perhaps I got carried away when it came to the rosette, which might have been more elegant if the diameter had been a little less. Below are a few photographs of the completed instrument.

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Unfortunately, the shellac experiments failed to reproduce the problem that I had with the polish that failed to harden. I put blobs of shellac from each of the containers of the stuff that I had in the workshop onto a sheet of glass and left them overnight: all hardened satisfactorily. So I can rule out the possibility that the shellac I was using was too old.

I also French polished a piece of scrap mahogany, using a lot of mineral oil on the rubber and building up a thickish layer as quickly as I could. That worked fine. So Bob Flexner was quite right when he said that it wasn’t the oil causing the problem.

I’m left without an explanation but I have learnt something. First, it’s always worthwhile to check that the shellac hardens using the ‘blob on glass’ technique before starting to polish an instrument. Second, mineral oil is an effective lubricant for the rubber and doesn’t compromise the quality of the finish. And third that, if the polish doesn’t harden fairly quickly, the best thing to do is wipe it off and start again rather than waiting around in the hope that it will harden eventually.

It looks as if  I’m wrong about the problem with non-hardening shellac that I mentioned in my last post. There, I suggested that it might have been due to using mineral oil to stop the pad sticking when applying the shellac. Bob Flexner emailed me saying that neither he nor the hundreds of people that he has taught have ever encountered any trouble with mineral oil. Indeed, the reason that he prefers mineral oil to linseed oil is that unless one is careful in removing all the linseed oil, it cures soft and gummy on the surface.

I’d like to get to the bottom of the matter, not least because I don’t want to run into the same trouble in future. So I’ve carried out some experiments to try to reproduce the problem using various types of shellac in combination with various types of oil to see if they harden differently. If anything useful comes of them, I’ll write about it.

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