Measuring of oil varnish heat

[Giovanni Corazzol]

I have a question about the use of earth colours, (raw umber) suggested by Fred.

 

I was reading somewhere that nowadays, many traditional earth pigments do not have the same source of the original, documented materials, they are just imitations, made with mixtures of (synthetic) iron oxides. So probably the drying properties are different, if Manganese and other metals can't be found in the modern products. It may be a good method for introducing iron in varnish, (there are many: rusted nails, steel wool etc.) if one wants a darker colour.

 

In conclusion, my observation was that those who want to replicate an original recipe closely, should check the source of those pigments also.

 

About temperature measuring: I have always used a glass thermometer. When making varnish I keep a long piece of wood with a channel in the middle, and place the thermometer in it when i do not use it, to make sure that the thermometer cannot roll and come into contact with some cold surface. For the same reason I do not use Pyrex containers anymore for varnish... only a metal enameled or ceramic coated kitchen pan

 

Giovanni

[Peter K-G]

Not sure where to put this "stupid" question

 

What is the main reason for the cooking? 

 

In the context of making varnish from:

 

Colophony (Rosin from pine resin)

Linseed oil

Turpentine (From pine resin)

 

This have been discussed (and maybe answered) over and over again in ongoing varnishing topics on MN right now.

 

(Releated question in my post http://www.maestronet.com/forum/index.php?/topic/328713-sizing-with-casein-hydraulic-lime/#entry591166)

 

The reason for asking is that I like to know and understand what's going on, and not start aimless experiments with cooking components.

 

And the whole varnish making thing seems so simple, so I can't understand the massive discussions around it.

 

Am I missing something

 

Peter

[tango]

Peter

 

Sometimes I feel like you. 

What I understood at the moment is that resin and the oil have to be integrated. We achieve this by different method, at differents temperatures (thousands of making ways  ).

I think the most important point is that the oil and resin be united, in only one thing.

There are another problems that complicate the stuff: the drying time, the excesive hardness, the opaque appearance and others.

This problems generate discussion.

Regards

Tango

[FredN]

I have a question about the use of earth colours, (raw umber) suggested by Fred.

 

I was reading somewhere that nowadays, many traditional earth pigments do not have the same source of the original, documented materials, they are just imitations, made with mixtures of (synthetic) iron oxides. So probably the drying properties are different, if Manganese and other metals can't be found in the modern products. It may be a good method for introducing iron in varnish, (there are many: rusted nails, steel wool etc.) if one wants a darker colour.

 

In conclusion, my observation was that those who want to replicate an original recipe closely, should check the source of those pigments also.

 

About temperature measuring: I have always used a glass thermometer. When making varnish I keep a long piece of wood with a channel in the middle, and place the thermometer in it when i do not use it, to make sure that the thermometer cannot roll and come into contact with some cold surface. For the same reason I do not use Pyrex containers anymore for varnish... only a metal enameled or ceramic coated kitchen pan

 

Giovanni

Hi Giovanni- I think I wrote Burnt Umber, the manganese is almost half the content found in raw umber. Manganese increases the brown in the final varnish and the reason for using burnt umber. Also the finest umbers sought through history by painters comes from the Isle of Cyprus and it is milled in Leghorn, Italy.

Regards following a recipe, the problem is there is no recipe how the old masters finished their inst's.  This would indicate it is something routine and simple enough to be part of the hand-me-down  journeyman's learning.  fred

[FredN]

Not sure where to put this "stupid" question

 

What is the main reason for the cooking? 

 

In the context of making varnish from:

 

Colophony (Rosin from pine resin)

Linseed oil

Turpentine (From pine resin)

 

This have been discussed (and maybe answered) over and over again in ongoing varnishing topics on MN right now.

 

(Releated question in my post http://www.maestronet.com/forum/index.php?/topic/328713-sizing-with-casein-hydraulic-lime/#entry591166)

 

The reason for asking is that I like to know and understand what's going on, and not start aimless experiments with cooking components.

 

And the whole varnish making thing seems so simple, so I can't understand the massive discussions around it.

 

Am I missing something

 

Peter

Hi Peter- If you were making a copal varnish you have to first heat it to over 600oF to crack (depolymerize)  it to make it oil soluble after it has laid in the ground and oxidized after thousands of years. With rosin, it doesn't have to cracked but  it is heated to drive off undesireables  that create after-tack, to add metals to raise the melting point, color it, etc. Heating the oil is done to make it closer to the gel point so when it is added to the resin it will take up oxygen and form a firm film in the shortest amount of time and hardened by the resin you added. The reference literature will tell you when linseed oil is heated to about 525o the internal structure of the oil molecule begins to change, the rearrangement results in the molecule being able to take up oxygen when spread out in a film, and hardening. At 525, this is a slow process and raising the temp to 600 speeds up the process considerably because with more or less every 10 degree rise in temp the chemical activity doubles. There are persons on MN who can tell you more about this, I'm not a chemist. So by using a higher temp you can get to the optimal state of the oil to add to the resin to form a gel in a reasonable amount of time. These are the reasons the components of a varnish are heated. Hope this helps.  fred

[Peter K-G]

Hi Peter- If you were making a copal varnish you have to first heat it to over 600oF to crack (depolymerize)  it to make it oil soluble after it has laid in the ground and oxidized after thousands of years. With rosin, it doesn't have to cracked but  it is heated to drive off undesireables  that create after-tack, to add metals to raise the melting point, color it, etc. Heating the oil is done to make it closer to the gel point so when it is added to the resin it will take up oxygen and form a firm film in the shortest amount of time and hardened by the resin you added. The reference literature will tell you when linseed oil is heated to about 525o the internal structure of the oil molecule begins to change, the rearrangement results in the molecule being able to take up oxygen when spread out in a film, and hardening. At 525, this is a slow process and raising the temp to 600 speeds up the process considerably because with more or less every 10 degree rise in temp the chemical activity doubles. There are persons on MN who can tell you more about this, I'm not a chemist. So by using a higher temp you can get to the optimal state of the oil to add to the resin to form a gel in a reasonable amount of time. These are the reasons the components of a varnish are heated. Hope this helps.  fred

 

Thanks, but isn't this about refining the components - rosin, turpentine and linseed oil.

(I understand you might not get good raw materials directly from Pine sap (gum, resin))

 

But If you buy higest quality of refined colophony (rosin) and refined/polymerized linseed oil.

 

Why not just dissolve colophony with pine turpentine (balsam turpentine from pine or what ever they call it, the best quality you can get anyway, I know what it is)

 

Then mix this solution (colphony&turpentine, which is then back to kind of it's original solution), with the refined linseed oil.

 

=> There is your varnish?

[Peter K-G]

And maybe the gentlemen from Cremona didn't cook their varnish at all! Maybe they just bought the best components, dissolved different rosins with alcohol and/or turpenite and just mixed their own varnish?

 

It had to be simple, they made a lot of violins!

[Roger Hargrave]

Exiting Florence, through the Porta a Pinti, there was an arch in the wall with an open space and a recess, all black, and full of a greasy lustrous soot. That was the place where the varnishmakers would go to cook varnish, it was not allowed in the city because of frequent exothermic reactions, which may have been the cause of fires in town.....

 

An  ex-violinmaker friend said that while she lived in Cremona she saw in an exhibit a paper for varnish order or something of the sort from an apothecary, she did not remember who was the maker....anyone seen this? Does it add up?

Q 1. The sooty wall space may have been where they prepared hot oils and pitch to defend the city in times of seage. This would certainly have been made close to the gates which were the principal weak points. 

Q 2. There is a book that has various itemes that a local apothacary suplied in Cremona at the time of Stradivari. I have not seen this book myself but I believe Andrew Dipper noted and perhaps even translated this work. Bruce may also be able to help. 

[Roger Hargrave]

Fred’s blending method is more or less what I do. I have also filtered my rosin varnishes and this definitely increases their 'brightness', but I am not sure that it is enough to bother with the mess. I find that it is usually perfectly usable without. I have never been much of a fan of copal or amber varnishes. They work well enough but they are more difficult to make and they are as Fred says, never quite as bright. ‘Bright’ is a good word to describe the difference between these varnishes, it is certainly better than comparing their ‘transparency’.  

PS by 'Rosin' I mean 'Colophony'. It is really not expensive whichj is another added bonus.  

[robertdo]

And maybe the gentlemen from Cremona didn't cook their varnish at all! Maybe they just bought the best components, dissolved different rosins with alcohol and/or turpenite and just mixed their own varnish?

 

It had to be simple, they made a lot of violins!

they might also have bought the ready made varnish.

I remember M. Darnton writing on his website that he is using a cold varnish made by dissolving mastic in turpentine and adding linseed oil. It works well as a varnish because mastic is easily dissolved in turpentine and oil. I think I tried doing the same with rosin, turpentine and oil. the result was not very good.

As for the Cremonese makers it seems now that the ground is more important than the varnish itself in the appearance of the varnish. So maybe the way you prepare a varnish is less important than how you prepare the wood to be varnished.

[Peter K-G]

Fred’s blending method is more or less what I do. I have also filtered my rosin varnishes and this definitely increases their 'brightness', but I am not sure that it is enough to bother with the mess. I find that it is usually perfectly usable without. I have never been much of a fan of copal or amber varnishes. They work well enough but they are more difficult to make and they are as Fred says, never quite as bright. ‘Bright’ is a good word to describe the difference between these varnishes, it is certainly better than comparing their ‘transparency’.  

PS by 'Rosin' I mean 'Colophony'. It is really not expensive whichj is another added bonus.  

 

I also have simple 30 min recipe with colophony, turpentine and linseed from Patrick Kreits book, similar to what you and many others do. The process is a little bit in different order but basically it's about mixing the components under heat.

 

But why the heat?

 

 

 

Why not just dissolve colophony with pine turpentine (balsam turpentine from pine or what ever they call it, the best quality you can get anyway, I know what it is)

 

Then mix this solution (colphony&turpentine, which is then back to kind of it's original solution), with the refined linseed oil.

 

=> There is your varnish?

 

 

[Peter K-G]

they might also have bought the ready made varnish.

I remember M. Darnton writing on his websive that he is using a cold varnish made by dissolving mastic in turpentine and adding linseed oil. It works well as a varnish because mastic is easily dissolved in turpentine and oil. I think I tried doing the same with rosin, turpentine and oil. the result was not very good.

As for the Cremonese makers it seems now that the ground is more important than the varnish itself in the appearance of the varnish. So maybe the way you prepare a varnish is less important than how you prepare the wood to be varnished.

 

This is what I have been practicing (buying ready to use products), never been completely happy with the outcome (I understand the process is more important than product, but..)

 

I have tested:

 

Hammerls spirit varnish - too brittle after some years, hard like glass

Hammerls Oil varnish La - like a furniture when finnished

Hammerls Italian balsamic oil - smells good, too shiny and never dries

Old Wood 1700 system 6 - best so far, but wears off too fast (might be a problem in my process)

 

Anyway, you never know what's in the products,  why and how they react.

 

Have to search for the mastic rosin dissolved in turpentine...

[CarloBartolini]

 

Q 1. The sooty wall space may have been where they prepared hot oils and pitch to defend the city in times of seage. This would certainly have been made close to the gates which were the principal weak points. 

 

Q 2. There is a book that has various itemes that a local apothacary suplied in Cremona at the time of Stradivari. I have not seen this book myself but I believe Andrew Dipper noted and perhaps even translated this work. Bruce may also be able to help

 

Maybe that explais the amount of soot described by Conti......love history's guessing game....  I knew I should have translated the whole passage of the book, instead of loosely quoting some parts.....but short in time, sorry...I hope you understand italian...thanks for the answers. Q2 also, I'l try to find it., thanks again.. 

 

Risalendo un po' la strada poiché quando le mura si avvicinavano alle porte il piano era in discesa, e continuando per la Porta a Pinti, in faccia al Vicolo della Mattonaia che metteva in Borgo la Croce si scorgeva il grazioso villino Ginori con le due cupolette a squamme gialle e turchine, ed in quel punto delle mura esisteva un vuoto ad arco come una gran nicchia tutta nera, e piena d'una fuliggine lustra come unta. Quello era il luogo dove i verniciatori, i mesticatori e i legnaioli, andavano a far le vernici, poiché non era permesso di farle in città, a causa dei frequenti casi in cui scoppiavano i matracci, e che potevano esser causa d'incendi.

In cotesta località, quasi deserta e fuori di mano, andavan pure i carradori a piegare i cerchioni delle ruote dei barrocci e dei carri; operazione che si faceva con sistemi molto primitivi, poiché facevano in terra un gran cerchio di grandi scheggie fatte coll'ascia nel modellare il legname, e vi mettevano sopra i cerchioni, che con delle grosse morse piegavano quando il ferro era rosso.

FIRENZE VECCHIA

STORIA - CRONACA ANEDDOTICA - COSTUMI

Giuseppe Conti - (1799-1859)

[Patrick KREIT]

Peter

 

Solution:  The product is suspended in the solvent.

Dissolution:  The product is incorporated into the solvent.

 

Some resins are soluble cold, others are not, but they are soluble at a certain temperature.

Sometimes a certain order must be followed or it precipitates!

 

www.kreitpatrick.com

[Peter K-G]

 

I also have simple 30 min recipe with colophony, turpentine and linseed from Patrick Kreits book, similar to what you and many others do. The process is a little bit in different order but basically it's about mixing the components under heat.

 

But why the heat?

 

 

 

 

 

Here is actually the best answer by Joe to my question:

 

http://www.maestronet.com/forum/index.php?/topic/328620-varnish-making-questions-for-the-chemists/#entry588994

 

I have a business idea; why not start a varnish making business, that cooks and sells varnishes with the exact recipie; components, temperatures, mixing. Everything transparent. This way violin makers kan choose what they want.

[Peter K-G]

Peter

 

Solution:  The product is suspended in the solvent.

Dissolution:  The product is incorporated into the solvent.

 

Some resins are soluble cold, others are not, but they are soluble at a certain temperature.

Sometimes a certain order must be followed or it precipitates!

 

www.kreitpatrick.com

 

Yes  I have read all day about this now, quite interesting actually

[FredN]

Thanks, but isn't this about refining the components - rosin, turpentine and linseed oil.

(I understand you might not get good raw materials directly from Pine sap (gum, resin))

 

But If you buy higest quality of refined colophony (rosin) and refined/polymerized linseed oil.

 

Why not just dissolve colophony with pine turpentine (balsam turpentine from pine or what ever they call it, the best quality you can get anyway, I know what it is)

 

Then mix this solution (colphony&turpentine, which is then back to kind of it's original solution), with the refined linseed oil.

 

=> There is your varnish?

I don't know much about the use of raw products to make a varnish. I do know that you can use Boiled Linseed Oil that has manganese and cobalt  driers to speed up the drying of the varnish. Cobalt is a surface drier and I think will create problems your way. Boiled linseed in the Great Period was made primarily with lead which behaves totally different, and its use now is prohibited.  If you read about rosin you learn it is very acidic and it has to be neutralized otherwise your varnish would eventually disintegrate. These are limed rosins, and the commercial varnish made with it is called Gloss Oil varnish. You have to neutralize the acidity,  raise the melting point and take advantage of the ability to color it with a metal.  fred

[FredN]

Fred’s blending method is more or less what I do. I have also filtered my rosin varnishes and this definitely increases their 'brightness', but I am not sure that it is enough to bother with the mess. I find that it is usually perfectly usable without. I have never been much of a fan of copal or amber varnishes. They work well enough but they are more difficult to make and they are as Fred says, never quite as bright. ‘Bright’ is a good word to describe the difference between these varnishes, it is certainly better than comparing their ‘transparency’.  

PS by 'Rosin' I mean 'Colophony'. It is really not expensive whichj is another added bonus.  

Hi Roger, You can add another word "bright and beautiful".  I think it is the high temp used making Copal varnish that you wind up with carbonized unfilterable stuff that dulls it. fred