MikeC

That was an interesting read.

I would like to see that paper considering I don't have a subscription to the Strad. Hopefully you can find it. What is meant by burnt bone? Wouldn't that just turn bones into carbon?

I like your Scottish accent!

Well I hope not that much of a peek haha

Here are tool marks on the inside of my ribs. If anyone ever takes the top off years from now they will say oh look it was made by a human not by a machine. Or if you want it perfect I suppose it could all be cut out by a laser.

Davide I'm curious about the 5 years old linoxin that you use in varnish. Have you tried putting that on bare wood? Linoxin only? to see what that would look like? I wonder how well it would seal. Since it is black in the undiluted form I wonder would it have much color in a thin layer in the wood. I am making some but it will be a few years before it's ready unless I use the fast method mentioned by Claudio in an old thread here.

Manfio's tutorial is here on MN. Also Davide Sora has some very good videos on the scroll carving process.

Sounds like a reasonable explanation to me. Also I think you are right about the back side of the drawing. Notes I found say that it is for the B form cello and revers side for the small B form. Pin pricks for transferring the form to an instrument.

It could be perhaps but I don't know how thick the paper is or how deep the ink penetrates. So that's a possibility. I wonder why many of Strad's drawings and other drawings from that time are made with dots or short dash instead of a solid continuous line.

I found a much better photo of the drawing posted earlier. It seems to have some circles with compass points near the right hand edge that look about the same size as the upper eye of the F hole.

I'm not satisfied with positioning yet either. Using the placement geometry I seem to get some asymmetry so I cut out my drawing and folded it half thinking my plate was asymmetrical but it's pretty darned close to perfect symmetry so my drawing must be off some even though I was careful in drawing it. I think I will have to move the F's around some to make them work well. I need to print out an F template or trace from the Titian poster.

Something interesting I noticed while playing around with the F hole positioning. The distance of the upper eye from the center line is a golden section of the distance of the lower eye from the center line. Maybe I'll do some pictures later to show that.

I think that violins made on the same form would be close enough in size and shape that they could use the same F hole positioning. So Strad could make one drawing and just use dividers or compass settings from that to do both sides. Maybe use a different drawing for each form. In this image I'm sure most of us are familiar with I noticed something in the dots that are hard to see since this isn't a good quality image. If you enlarge it and look carefully there is a mirror image of the side. I'm not sure what the significance of that is but it's there. I darkened the dots to make them more visible.

Hi Andreas thanks for your comments. I have a couple questions. When you say the difference to the original Cremona system is that he works from the outside to the inside. What is the alternative? What is the 'original Cremona system'? You say DG did it differently do you have any idea of his method? my outline is a little bit distorted that's why I had to scrap my first drawing and start over. Marking the center line more carefully but still the center points for the F holes are off slightly one side vs the other side. I may have to cheat a little bit Strad style.

working on contours. It's still a bit asymmetrical especially in the lower bout but getting close.

I'll have to dig up my old textbook on quantum mechanics to figure out what Jezzupe is talking about

I second that motion.

How much of the so called 'golden ground' color is due to yellowing of later over coatings of say french polish I wonder?

I'm no expert so take my advice with a few grains of salt. Try going thinner, get down to 1mm. I seem to remember reading that DelGesu went even thinner than that in the tightest part of the curve where it glues to the corner block. for a bending iron I use an iron pipe clamped in a vice and heat it with a propane torch so I have no idea what temperature it is but a drop of water on it will instantly vaporize. When I put the rib to the iron I can feel it soften and start to bend. If it starts feeling stiff I'll wet it again, make sure the iron is still hot enough and then bend it some more vs. trying to do the whole bend all at once. I do the smoothing and scraping on one side while the rib is still flat and then do all the planing and thinning on the other side which will end up being on the inside of the finished instrument where tool marks wont be seen.

. Looks like my images didn't load the first time so here they are.

Attempting to layout the position of my F holes using the old Cremona system. Lower hole center is where the golden section intersects the triangle which is one third the pin length. Upper hole centers is a radius of the hypotenuse of 1/4 the triangle height and positioned in from the C bout sides radius 1/4 the triangle height. Compass points on the C bout edges can either be from a radius of the hypotenuse to 1/4 height or from half the base length, there's not much difference either way. Is that confusing enough? heh. I made a few mistakes and restarts along the way.

how thick are the ribs? It's hard to tell from the picture. Get them down to about a millimeter thickness and they will bend easier. I like to use a leather strap instead of a metal one but not sure if that would make a difference. It works anyway.

He says, quote "and now we can see what is called the dichromatic quality of the famous Cremonese varnish". So he seems to be implying that this is an old Cremona instrument. If it's French or German or whatever it is, I like the effect.

yes same as in soap bubbles

I think what you're seeing in these photos are thin film interference. https://en.wikipedia.org/wiki/Thin-film_interference There is a video Kevin Lee luthier where he is doing some cleaning of what he claims to be an old Cremona violin. At the end of the video showing the varnish at one angle it's golden in color and at another angle the thin red varnish appears. It's a very nice effect. Attacking a Strad with steel wool.. really? heh but seriously skip to time stamp of about 44:45 and check out the dicromatic effect on the ribs. Does anyone know what instrument this is?