Urban Luthier

I hollow grind my gouges on a Tormek and hone freehand on stone grits you mention above. The Tormek works well for restoring and chisels small plane irons and gouges, but is simply too slow at removing large amount of metal on larger plane irons. If I had to do it all over I'd follow the advice given earlier in the thread

Love the colour!

Before reading any further - did you measure the ingredients by weight or did you measure grams for the colophony and ml for oil? if you did the latter you may well come out with a varnish that is near solid depending on how long you cooked it for.

Stunning work as always Davide!

I find gouge sharpening the hardest of all and I'm looking for ways to improve. I hollow grind the bevel and use the bevel to register on the stone and sharpen free hand

Always enjoy seeing your work Dave!

There is a very simple description of how Strad formed his purfling mitres in Sacconi which @Michael Darnton covers. Roger also covers this in several of his articles about how the Amati's shifted the outer bout curve toward the inner bout to form the mitre - Girolamo being the most extreme I think (also because he laid the purfling closer to the edge resulting in those very long mitres. I can't seem to find the reference but will look later.

I've made a couple of violins off this drawing - it is one of Roger's. It is a very good model. Here is what I came up with. I'll post the PDF later.I have archings as which I can share. Very curious to see what you come up with @Claudius My drawing is more of a copy of the outline and the inner mould was based on an offset that takes into account the varying overhang.

Always a joy to see your work and watch your videos Davide!

Beautiful work Jim - congratulations!

Glad you enjoyed the new digital edition! I will respond a little more... and please know I'm not being critical of you in any way - I really enjoy your work! The method described by Roger for Baroque construction shares similarities with Sacconi but it is quite different. The asymmetries discussed are result of the working method of attaching the neck to the freed rib garland before the body outline was taken - it is just the way they did it (guitar makers worked the same way). The neck was used to pivot the body around locating pins to get the centre line causing the typical distortion we see virtually every Cremonese instrument from the period - one can see the results by overlaying the outline of strad posters etc. As for geometric construction - just because Roger didn't mention it in the del Gesu book or his subsequent articles, doesn't mean he didn't explore the topic. The viola shown in the Bass book was drawn up following @francoisdenis methods. As for my own opinion - I believe, based on the evidence we have, that many violin, lute, guitar makers of the period were indeed extraordinary designer / crafts people (as you suggest) with exceptional drafting skills. IMHO it is very likely the designs of Andrea Amati were made with Geometric system - there are many systems shared here and I like the work you have done. The one geometric principle that seems to be consistent with the Amati's at least is the centre bout forms part of a perfect ellipse - something we don't necessarily see with modern drawing methods. Did Strad use a system? Perhaps when exploring a new model. I believe Stuart Pollens hit the nail on the head with Strad. It is quite possible he simply took an old mould, traced it and made modifications by hand and eye and just got on with it. Yes the forms are asymmetrical but it wasn't an issue because they had a defined way to align the neck and place the f holes. And lastly I've read Giorgio Vasari (I have a graduate degree in the history of Art and Architecture). The only thing one will learn from Vasari is that he considered himself the ultimate manifestation of the 'Italian Renaissance'.

Since Roger Hargrave's Working Methods of del Gesu has been mentioned a few times in this thread, I thought I would post a link to the revised digital edition of his sections of the Biddulph book. For those who haven't seen it, this digital edit much easier to follow than the one posted on his site.

del gesu plowden sept 2024-Model.pdf I played around with a plowden drawing as well - not a geometric reconstruction but a tracing from the ct scan. I traced the outline but used a series of perfect circles and an ellipse in the c-bouts. Surprising how easy it was to get a shape near identical with very basic geometry. Drawing was done in Autodesk Fusion in just a few minutes. The hardest part is scaling and sizing the ct scan!

I don't disagree with you - many here do heat their resin at a higher temp to get the colour but that is not what Roger did. He can't reply so I will. He certainly did appreciate the effect of temp and documented clearly in the bass book. Direct Quote... "The method(s) I used for combining these ingredients was based on two or three further snippets of information. The first of these concerned the length of the colophony molecules. These were found not to have been significantly altered. Accordingly, White had concluded that the colophony had not been cooked at a high temperature. He suggested that it had probably been heated just hot enough and long enough to blend it with the oil and mastic. His conclusion about the mastic was that it had probably been added as plasticizer, last of all." P121 Everyone, by the way, the recipe i posted earlier in the thread is the actual varnish he used on the bass and was not published in the book. The recipe in the book is based on colophony which was pre cooked slow and low for about a week Colophony varnish recipe 500 grams colophony (resin) 50 grams mastic tears 450 grams cold pressed linseed oil Heat the linseed oil to 200C Slowly add the colophony (resin) and stirred for at least 2 hours Allow the oil/resin mix to cool a little. Add the powdered mastic tears last of all and stir for 1 hour more It is extremely important NOT to remove the cooking pot from the stove and place it on a cold surface. This can cause a violent reaction. The still warm, but NOT HOT varnish can then be filtered.

This is very large topic discussed in various threads. Try searching a bit - easy to loose oneself however. I can speak to Roger's workflow, the subject of your original post. Roger did not use dyes or pigmented lakes in his varnish workflow for the bass. The colour is from the varnish alone (resin cook). However, his student and colleague, the late Neil Ertz, did use madder lakes to colour his varnish. Neil was very generous and shared his working methods in the forum. I can only speak for my self, as an amateur, I find his workflow easy to follow. MN members have shared literally dozens of different methods when it comes to making coloured lakes.