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Science and "Evidence"


Peter K-G
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On 6/5/2021 at 10:37 PM, Peter K-G said:

Quite often established "evidence" is the truth.

And you don't dare to question The Truth, do you?

Roger Hargrave's site is undoubtedly one of the best sites for the "truth".

However there are two truths/evidences that are established facts that I want others opinions on, regarding old cremonese violins.

1. The purfling and channel  were done after the soundbox closed

=> evidence: end block pins  are under the purfling

Question: this is the only established facts base?

2. Most of them (old Cremonese) has been re graduated

=> evidence ??

 

The Stradivari Science myth that annoys me is the belief that he dried his varnished instruments in direct sunlight.

Where does this come from?

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19 minutes ago, Strad O Various Jr. said:

Probably Stradivari saying that the instruments require the direct heat of the sun to dry! Its in the Hill book if you don't believe me.

Exotic-sounding excuses for work delays are as old as mankind. After all, it wouldn't have sounded as good if Stradivari had said that he had just forgotten about the fiddle, or hadn't gotten around to it yet, or that his hemorrhoids were in such a severe state of flareup that he could hardly work, or that Omobono had yet again run off with another trollop.  ;)

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13 minutes ago, Strad O Various Jr. said:

Probably Stradivari saying that the instruments require the direct heat of the sun to dry! Its in the Hill book if you don't believe me.

Go on then give me the quote?

Without misinterpretation.

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6 minutes ago, David Burgess said:

Exotic-sounding excuses for work delays are as old as mankind. After all, it wouldn't have sounded as good if Stradivari said that he had just forgotten about the fiddle, or hadn't gotten around to it yet, or that his hemorrhoids were in such a severe state of flareup that he could hardly work. ;)

And of course you and virtually all of your colleagues make use of UV light boxes to dry varnish, how do you propose 18th century builders did that without direct sunlight?

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4 minutes ago, David Burgess said:

Exotic-sounding excuses for work delays are as old as mankind. After all, it wouldn't have sounded as good if Stradivari said that he had just forgotten about the fiddle, or hadn't gotten around to it yet, or that his hemorrhoids were in such a severe state of flareup that he could hardly work. ;)

He probably preferred warm sunny weather for varnishing. Who doesn't? 

Isn't it more likely that toni's UV box was a window? And that he didn't hang em from the washing line? That would have pissed off Mrs Strad wouldn't it?

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12 minutes ago, Strad O Various Jr. said:

And of course you and virtually all of your colleagues make use of UV light boxes to dry varnish, how do you propose 18th century builders did that without direct sunlight?

A light box is not necessary, but does reduce the probability of damage from rain, bird poopage, and kids throwing rocks. ;)

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Rosin and oil varnishes of the type we have evidence Stradivari used require UV light exposure to dry in any reasonable amount of time, the only source of UV light Strad had access to was sunlight, later in the 18th century spirit based varnishes that dry without UV light were developed and perhaps became popular for that reason, among other reasons.

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32 minutes ago, Strad O Various Jr. said:

Rosin and oil varnishes of the type we have evidence Stradivari used require UV light exposure to dry in any reasonable amount of time, the only source of UV light Strad had access to was sunlight, later in the 18th century spirit based varnishes that dry without UV light were developed and perhaps became popular for that reason, among other reasons.

 What type of UV? How much exposure? What temperature? For how long?

Don't you think it's more likely that he used the top room of the house. The warmest room in summer and the one with the sunniest windows?

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6 minutes ago, Strad O Various Jr. said:

He still needed direct sunlight, the problem with windows is they only provide direct sunlight for shorter periods of time, if at all. Not saying he couldn't have used windows, but I don't see any major reason why he couldn't have used the backyard, or did he live in a  bad neighborhood?

You don't need direct sunlight. It's all part of the myth. 

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1 hour ago, Strad O Various Jr. said:

He still needed direct sunlight, the problem with windows is they only provide direct sunlight for shorter periods of time, if at all. Not saying he couldn't have used windows, but I don't see any major reason why he couldn't have used the backyard, or did he live in a  bad neighborhood?

Strad's varnishes may not have required direct exposure to sunlight to dry.  Both lead and manganese are a common theme in his varnishes.  While a light box or sunlight certainly speeds things up, in my experience varnishes that include lead and manganese will dry in a workshop situation. 

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I remember an article about hooks being found on the top floor of Stradivari's domicile which had large windows or openings. The speculation was that he hung his instruments there so that they were exposed to sunlight.

 

 

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Sure sunlight speeds up things but my raw linseed oil cooked with lead acetate/oxide that I made myself does dry overnight in my basement shop with just small northern window even in "not so thin" layer. Thicker coat of varnish made of this would require week or two to harden enough to be used...

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17 minutes ago, HoGo said:

lead acetate/oxide

Please, can you tell me how you do it? I made various driers but never lead acetate. Now it is time. I have lead from old tubes. I cut small pieces plus -> vinegar (or acetic acid) + Hydr. peroxide? And when the oxide is ready, do I have to dry it and use it as powder inside varnish? 

I use pale siccative for years with no problems at all - except it is a bit slow / does lead acetate has any difference or it would be a time loosing process?

Thanks

 

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I don't remember the recipe or where I got it, (most likely in one of the ld books or internet, though back then it was more likely the books), but I remember the process I did... I just took flat pieces of lead and left them in vinegar for a week till it created "crust" then took the lead out and left it in the sun for few days to dry and oxidize on surface and then scraped all the whitish stuff from surface and repeated few times. I don't remember where I got this idea but I managed to collect few teaspoons of the stuff and the recipe told it is lead oxide / acetate... I mulled it into powder. I guess starting with fine filings of lead would transform them completely faster than this process, but I was not in hurry...

Make sure your lead is pure lead, not  alloy with tin or other metals (I got 50kg Pb ingot directly from producer)

When I cooked the oil, I took refined linseed oil and cooked for 15 minutes or so in gentle boil and added something like 1/4 teaspoon or so per 100ml  and stirred/mixed and boiled for another 15 minutes or so. Part of the lead settled to bottom of jar later so I probably added more than needed. I did this more than 20 years ago and still have leftover oil in the jar which is still liquid and dries well when applied over wood (I smeared it with finger without any forceful wiping)

You can add this into oil varnish during/after cooking.

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