Stradivari's golden ground varnish


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12 minutes ago, Don Noon said:

I'm trying out some experiments now as well, to see how UV affects oil penetration and spread.  Some drops of various things are on a piece of white paper hung vertically in the lightbox, and an identical set is in a closed metal cabinet.

Sure, lubrication oils probably wet better and definitely are made not to dry, but until drying oils dry, they act a lot like lubricating oils.  

One other point... if a thinner is involved, there are two phases of "drying"... one where the thinner evaporates, and another where the oils polymerize.  Spreading might slow down after the first, but won't stop until the second.

If the photograph is of an area where there is zero runout, then there can't be penetration farther than one cell, even with oil spread.  With figured maple, or on sloped cuts of arching, that's different, and it matters how quickly the oil dries vs. how fast it spreads by capillary action.  Try sealing the endgrain of spruce with linseed oil sometime... it's a sponge.  Or figured maple... it will sit on the surface between flames, and sink in badly on the flames.

Does the end grain matter so much? I want more oil at the edges and less in the middle.

By applying a very small amount initially and rubbing it dries very quickly. And I use raw linseed oil, mucillage and all, no driers.

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5 minutes ago, sospiri said:

By applying a very small amount initially and rubbing it dries very quickly. 

"Disappears" I think is more likely.  I'm not sure how you can tell that the oil is actually polymerized and "dry".

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2 minutes ago, Don Noon said:

"Disappears" I think is more likely.  I'm not sure how you can tell that the oil is actually polymerized and "dry".

True.  As David highlighted linseed oil gains weight and the weight reduces as polymerization proceeds.  Given the tiny amount of oil it is virtually impossible to measure in the making process. The capillary action is faster than the polymerization process in the oxygen starved environment.

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4 minutes ago, Don Noon said:

"Disappears" I think is more likely.  I'm not sure how you can tell that the oil is actually polymerized and "dry".

Rubbing brings the oil back up to the surface. It also gets very hot very quickly. Hot enough to burn your skin, so you stop immediately you reach that point, reckoned to be 80 degrees C.

Polymerisation over however long is part of the mystery. Dry to touch is my first concern before I apply another layer. The well know effect of linseed oil is to darken the tone  but I'm certain that rosin/ turpentine brightens the tone and increases the effect of the rosin on the bow, improving touch sensitivity.

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5 minutes ago, joerobson said:

True.  As David highlighted linseed oil gains weight and the weight reduces as polymerization proceeds.  Given the tiny amount of oil it is virtually impossible to measure in the making process. The capillary action is faster than the polymerization process in the oxygen starved environment.

Yes, so care must be taken to minimize capillary action and maximize polymerisation.

 

 

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My linseed oil application strategy this time has been to place a few dots of thick stand oil on a rag, and let them spread overnight, leaving it dispersed enough on the rag that it is barely visible on my fingers when rubbing it on the wood with the rag.  This is immediately put under UV for 24 hours, then the next coat etc.. Nothing has come through the 1mm thick highly-figured rib sample. To get a better idea of penetration though, I'd probably need to add some intense color, and carve into the surface of the wood after things have dried.

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2 hours ago, sospiri said:

Thanks for the information Davide. But why not put linseed oil straight on the wood if it can be sealed with a very small amount?

Richard's photograph shows a penetration only one cell deep. 

Anyone can put it if they want and if done carefully and in the right process. But I don't use it, so I'm not the right person to recommend it and I don't want to take responsibility for any problems that may arise.

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1 hour ago, MANFIO said:

We have to destroy Stradcentrism.... the best violin golden ground was made by Andrea Amati.... go to Cremona and see it with your eyes in the ˜Carlo IX" 1566 violin by Andrea Amati....

This one?

amati.jpg.da29e367b9a5a8f72a854031dd079aac.jpg

Looks like a simple formulat to me: 

  1. apply a clear-ish varnish
  2. allow varnish and wood to age 450 years

Stradcentrism or Cremonacentrism with the focus of finding out exactly what they did I think is doomed to failure without accounting for the aging effects on wood and varnish.  If you want to copy the appearance today, you have to do something other than exactly what they did.

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I suggest you all reread the book "Violin Varnish" by Helen  Michetschlager--Koen Padding made a lot of progress on this issue.  If you are intrepid and also reread Hargrave's book on Basses, you will make a lot of progress in addressing all the issues.  This problem of ground never seems to go away.

Padding never left any detailed notes.  It is my surmise he left this stage out because it was so obvious to him.  I think he arrived at his conclusions by studying how artisans treated wood and canvas at the time these musical instruments were made.

Mike D

Edited by Mike_Danielson
needed to clarify the language
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I thought I’d take some macro photos of different bits of wood I have lying around to add to the discussion.  These are (except for the maple) saddle cutouts from my instruments I’ve saved on a board for times like these.  All of them have prepared linseed oil as the ground.  The maple is a scrap I smeared about 100 microns of oil on a month or so ago to test a new batch I had made.  It’s been tough and insoluble for the last three weeks.  To try and get it to penetrate further, I stuck it in the oven for an hour before I took the pictures.  It didn’t have any affect that I could tell.  3ADB5A61-67AA-4D6A-8C72-C113D405733A.thumb.jpeg.04d8129cd9454599762c0831497ab39f.jpegD08CAC30-1596-4924-BC52-D773ED6A2AA4.thumb.jpeg.3c108817b88afdb1e1dffd3a98fbcdd4.jpegC9306DE5-AAB8-44B0-A386-88605CA5A1EA.thumb.jpeg.78c3136653ac3bdd7bd0585fd9472d0d.jpeg09527440-8783-41D0-88E7-9D1E707F7D1F.thumb.jpeg.7b159166e066d9fc488645bfbace7659.jpeg
This sample is from a top with c.150 year old wood.  The maximum endgrain penetration was about 250 microns.B3521B83-4408-4EB9-A160-321281BB3790.thumb.jpeg.21a28486bfb5379ab1c784cbf0b0fa27.jpegE362BC34-8DCF-40EF-9021-38499BEAA12E.thumb.jpeg.7660ad4a4e3183c55fd7fff4877f0cce.jpeg

 

This sample shows quite a bit of stain penetration.  The wood was cut in the 1980s.  No measurable oil penetration that I could find, although the stain had saturated it pretty well.  

0FDEFBBE-349A-41F2-99CA-484FD0AB3D74.thumb.jpeg.8072b68ddd267675a069bd1112c25745.jpeg6A342265-5930-4E5D-BC4F-5EE4D8189060.thumb.jpeg.1a7af0f688c04931047c13d5064957b2.jpeg

This last one was wood I cut a few years ago, and has minimal penetration of both stain and oil.  6ECF2C8D-9C8D-4AD6-8BF4-EE3D593B0C9F.thumb.jpeg.737c31114359f24d7ef65bb5b33707a1.jpegFD2D5E77-D40E-4076-A4D5-63E6CC6B85DF.thumb.jpeg.ff1149d44c49bd1fc83e1530bd357752.jpeg

 

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Advocatus Diaboli, you need to look at these X-sections under the high magnification of an electron microscope in order to see the stratigraphy.  That is, determining oil penetration depth as well as any other layers.

I have not seen any data from Echard or other scientists that points to the use of flaxseed oil penetration as a ground.  Can anyone quote any one who has made this observation?  

Your X-section of the 150 year old wood shows the coloration of the wood that takes place with time, and that will help with coloring the ground layer.  In other words, the color we are trying to match comes with time.

Mike D

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6 minutes ago, Mike_Danielson said:

Advocatus Diaboli, you need to look at these X-sections under the high magnification of an electron microscope in order to see the stratigraphy.  That is, determining oil penetration depth as well as any other layers.

I have not seen any data from Echard or other scientists that points to the use of flaxseed oil penetration as a ground.  Can anyone quote any one who has made this observation?  

Your X-section of the 150 year old wood shows the coloration of the wood that takes place with time, and that will help with coloring the ground layer.  In other words, the color we are trying to match comes with time.

Mike D

I'm sure del Gésu got a lot of mileage out of his SEM. 

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2 hours ago, Mike_Danielson said:

Advocatus Diaboli, you need to look at these X-sections under the high magnification of an electron microscope in order to see the stratigraphy.  That is, determining oil penetration depth as well as any other layers.

I have not seen any data from Echard or other scientists that points to the use of flaxseed oil penetration as a ground.  Can anyone quote any one who has made this observation?  

Your X-section of the 150 year old wood shows the coloration of the wood that takes place with time, and that will help with coloring the ground layer.  In other words, the color we are trying to match comes with time.

Mike D

Echard is the one who’s repeatedly found what appears to be linseed oil in the first few Cell layers, presumably as a ground.  
 

SEM would be great if I were interested in trying to see how deeply trace amounts penetrated.   From a practical standpoint, however, it’s pretty easy to measure the depth of saturation under UV using a light microscope.  If we’re worrying about compounds in the wood, I’d be a lot more worried about salt from sweat than I would be drying oils.  I suspect most, if not all violins have sweat from the maker in the wood, but not enough to really affect anything. 

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9 hours ago, Advocatus Diaboli said:

 All of them have prepared linseed oil as the ground.  The maple is a scrap I smeared about 

Interesting pics AD.   You say 'prepared' oil.   What do you mean by prepared?  

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Some thoughts after reading all this.  From Echard it's only oil,  from B&G it may have some resin content.  Some of you are concerned about oil penetration but that has been demonstrated not to be an issue.  But if it is a concern then B&G also detected protein which could be a sealer to prevent penetration of oil.  Davide Sora in one of his videos shows application of a dilute casein as a sealer.  So finishing steps,  first apply a dilute protein sealer if you think it's needed to prevent oil penetration, then apply whatever stain then LO or uncolored varnish then colored varnish. Why would Strad and the others use plain LO rather than uncolored varnish? presumably they would have had both available. 

Properties of the ground has been described by some as very resistant to solvents, on the other hand some time ago on another thread there was mentioned that a Strad had been set down on an alcohol rag that was used to clean strings and when lifted, the ground had been removed down to bare wood.  So is it solvent resistant or not?

  After enough time LO becomes alcohol soluble as seen in Sora's five year old linoxin used as a component in varnish. .   I had a sample of thirty year old LO that looked and behaved exactly as his,  unfortunately not enough to use for varnish making.  

My questions remain,  are the old grounds solvent resistant or not? is it just LO or uncolored varnish?  Are the old grounds really all that golden yellow or does that apparent color come from later over coats of polish? 

Excuse all these random thoughts.. I'm just thinking ahead to the finishing process on my current VSO build.  :) 

 

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