"Copperas" in oil varnish?

[Andrew tkinson]

Iam sure that someone on Maestronet will have tried this so I searched and searched and searched again but couldn't find anything about it on this site. So I thought I would risk asking  couple of questions!

I recently looked at the old book, via the magic of the internet, " The Art of Painting in Oyl" by John Smith, 1705 and he describes making linseed oil dry quicker by adding "copperas"  that has been calcined/burned on a fire shovel, I presume this is ferrous sulphate and the heating maybe drives off the water of crystallization and turns the green vitriol/copperas white. Here is what he writes

The next page he describes "one inconvenience" of this is that it makes the oil a "deep reddish" colour!

I read this and thought this deep reddish colour sounds like it would be nice on a violin.

I seached on Maestronet and on the internet generally and could find nothing so please forgive me if I am asking dumb questions,

Has anyone tried this and does it work well as a drier?

Is there a risk of the iron in the oil turning dark over the years, like some of the very dark violins that originally were red?

Any information and advice will be gratefully received, in the meantime I feel a strong urge to go off and polish my fire shovel!

[MikeC]

That sounds quite interesting Andrew!  Although I'm leery of using anything with iron in it.  Afraid it might turn black over time.   

[joerobson]

Not in my repertoire

[LCF]

Wikpedia says: 'The name copperas dates from times when the copper(II) sulfate was known as blue copperas, and perhaps in analogy, iron(II) and zinc sulfate were known respectively as green and white copperas.'

 

Brewing that up with resin, Jackson M would probably say it makes metal rosinates. Chemically speaking it might be similar to liming although the pH is different. It is similar in that somehow a divalent or trivalent atom ( iron, zinc, copper, lime, aluminium, calcium etc) is forming a complex with two or more resin molecules (or oil, or both). Iron and zinc both have some drying action btw. 

 

Several people have written of the risk of iron turning varnishes black over time but I think it 'depends'. Based on similar antique recipes, I made varnishes 45 years ago with ferrous sulphate and with zinc sulphate in approx ratio of 1 level tsp of copperas to 100g resin (and 150ml oil). Either/or, or both. They are definitely a bit darker now in the same way that old newsprint would be if left in the sunlight, but they are still clear in the bottle and can still be brushed out, and dry, although drying a little slower than I remember. Anything that didn't combine in the cookup was simply filtered out. 

45 years on pieces of wood knocking around my workshop through various moves in an Australian climate is probably as good a test as anyone else can provide as validation. Will you be concerned if your varnishes get a bit darker in the next 45 years? Just don't use the whole shovelful!

 

 

Btw i wonder what effect gypsum, calcium sulphate, might have??? 

[LCF]

@jefcostello  have you tried this? 

 

We do not have Moles here but we do have Echidnas whixh are capable of trashing your lawn overnight in much the same way. 

In chemistry a Mole is a measure of how many molecules there are in some thing. Perhaps I should use Echidnas as my units, or Echs? However by a quick calculation there are 0.013 Moles of anhydrous iron sulphate in 2 grammes,  and 0.33 Moles of abietic acid in 100g of rosin. Multiplying the sulphate by 2 = 0.026 because it is an Fe++ iron, the ratio of moities is very low approx 0.08:1  , 8%, so the Fe++ won't interact with many resin molecules and it will be mostly business as usual. Anhydrous zinc sulphate ratios are similar. 

 

Jackson M's rosinate varnishes will have much more zinc( or alumium)  than this. I don't know if he uses iron in any if them?  A lot of people add a little burnt umber = iron plus manganese, or use specific thinned manganese or tin soaps which are driers. Japan driers etc. If you are grinding lakes into your varnishes that also adds a quantity of polyvalent metal ions. 

 

 

Edited April 29 by LCF
Arithomancy

[jefcostello]

@LCF

omg

When I was 16, I asked my teacher how the electron cloud was calculated. The teacher said don't worry about it, it's a genius guess. I knew I didn't like chemistry, so when you made your own dyes, I just watched quietly...

If you have a way that doesn't use ionic solutions I'd love to try it. Our education made me learn so much in high school, but I forgot it all after graduating from college! In fact, I hated chemistry.

Do you want me to boil the copper powder with the linseed oil?

[Andrew tkinson]

1 hour ago, LCF said:

@jefcostello  have you tried this? 

 

We do not have Moles here but we do have Echidnas whixh are capable of trashing your lawn overnight in much the same way. 

In chemistry a Mole is a measure of how many molecules there are in some thing. Perhaps I should use Echidnas as my units, or Echs? However by a quick calculation there are 0.013 Moles of anhydrous iron sulphate in 2 grammes,  and 0.33 Moles of abietic acid in 100g of rosin. Multiplying the sulphate by 2 = 0.026 because it is an Fe++ iron, the ratio of moities is very low approx 0.08:1  , 8%, so the Fe++ won't interact with many resin molecules and it will be mostly business as usual. Anhydrous zinc sulphate ratios are similar. 

 

Jackson M's rosinate varnishes will have much more zinc( or alumium)  than this. I don't know if he uses iron in any if them?  A lot of people add a little burnt umber = iron plus manganese, or use specific thinned manganese or tin soaps which are driers. Japan driers etc. If you are grinding lakes into your varnishes that also adds a quantity of polyvalent metal ions. 

 

 

 

47 minutes ago, jefcostello said:

@LCF

omg

When I was 16, I asked my teacher how the electron cloud was calculated. The teacher said don't worry about it, it's a genius guess. I knew I didn't like chemistry, so when you made your own dyes, I just watched quietly...

If you have a way that doesn't use ionic solutions I'd love to try it. Our education made me learn so much in high school, but I forgot it all after graduating from college! In fact, I hated chemistry.

Do you want me to boil the copper powder with the linseed oil?

Hello LCF and jef, 

I think the Australian unit for the number of molecules in a thing should be the Puggle - or Echidna Puggle to be more exact - as a Puggle (baby Echidna) is nearer in size to a Mole?

Edit. Here is a picture of an Echidna Puggle 

Anyway, I have ordered some Copperas - Iron Sulphate - and will have a go at making some deep reddish coloured drying oyl in the next couple of weeks. If it is a failure I can use the iron sulphate on my lawn!

I too am not the greatest at chemistry so will accept any advice that I am given. I have just looked up the weight of a level teaspoon of sugar and the internet seems to say it is just over 4g so I reckon one level teaspoon of Iron Sulphate granules should be about 4g?

I wonder what a level fire shovel of calcined copperas weighs?

[LCF]

1 hour ago, jefcostello said:

@LCF

omg

When I was 16, I asked my teacher how the electron cloud was calculated. The teacher said don't worry about it, it's a genius guess. I knew I didn't like chemistry, so when you made your own dyes, I just watched quietly...

If you have a way that doesn't use ionic solutions I'd love to try it. Our education made me learn so much in high school, but I forgot it all after graduating from college! In fact, I hated chemistry.

Do you want me to boil the copper powder with the linseed oil?

Take 100g rosin.

Warm it up to melt and fizz off.

Then add 2g FERROUS sulphate ( iron sulfate).

Then cook as hot as you like. 

Then make varnish. 

 

 

It's not copper sulfate, not the blue stuff. 

 

 

[LCF]

Re Moles vs Echs

 

i was thinking more of questions like: if Echs squared = 32.9 what is the reciprocal of Echs divided by Pi.

 

Below is a photo of how the parents let themselves out of our rabbit proof fence after spending a night on the ant.

[LCF]

1 hour ago, Andrew tkinson said:

 I have just looked up the weight of a level teaspoon of sugar and the internet seems to say it is just over 4g so I reckon one level teaspoon of Iron Sulphate granules should be about 4g?

 

I just tested and got 4.8. But I was originally using the common heptahydrate version which has about 1/2 the amount of iron per gram. It's all a bit vague. At molten rosin temperatures you can probably forgo the shovel.  

 

1 hour ago, Andrew tkinson said:

I wonder what a level fire shovel of calcined copperas weighs?

Too much!

[jefcostello]

1 hour ago, LCF said:

Take 100g rosin.

Warm it up to melt and fizz off.

Then add 2g FERROUS sulphate ( iron sulfate).

Then cook as hot as you like. 

Then make varnish. 

 

 

It's not copper sulfate, not the blue stuff. 

 

 

Just to confirm, it is Fe2(SO4)3, right?

[LCF]

https://en.m.wikipedia.org/wiki/Iron(II)_sulfate#:~:text=Iron(II) sulfate (British,SO4·xH2O.

[FiddleDoug]

I don't think that it has anything to do with with things like pH. Metal salts are well known as siccatives (drying agents) for paints. There are several chemical mechanisms for this. I have used transparent iron oxides in some varnish, and you can't store it. It starts to gel within hours. From a quick Google search:

Examples of Siccative Salts:

• Cobalt linoleate, cobalt oleate, cobalt naphthenate: Common cobalt-based driers.
• Manganese naphthenate: A popular manganese-based drier.
• Lead oxides (litharge, massicot): Historically used, but can be toxic.
• Zinc vitriol: Another historical drier, often containing other metal sulfates.
• Iron and zirconium: Less commonly used, but can also be effective. 
   

[LCF]

2 hours ago, FiddleDoug said:

I don't think that it has anything to do with with things like pH. Metal salts are well known as siccatives (drying agents) for paints. There are several chemical mechanisms for this. I have used transparent iron oxides in some varnish, and you can't store it. It starts to gel within hours. From a quick Google search:

Examples of Siccative Salts:

• Cobalt linoleate, cobalt oleate, cobalt naphthenate: Common cobalt-based driers.
• Manganese naphthenate: A popular manganese-based drier.
• Lead oxides (litharge, massicot): Historically used, but can be toxic.
• Zinc vitriol: Another historical drier, often containing other metal sulfates.
• Iron and zirconium: Less commonly used, but can also be effective. 
   

I think you can add calcium and aluminium to that list. And tin. The quantities required are often less 1%, sometimes less than 0.1%  There was a pdf linked some time ago with details of various metal driers. 

'Zinc vitriol' is same as white vitriol or white copperas, zinc sulphate. 

I once made my own lead drier by cooking red lead with a little hot resin. It made a very dark rosinate soap, very quickly. Those napthenates, oleates, linoleates and octanoates are also metal soaps, salts of fatty acids. 

[Andrew tkinson]

13 hours ago, LCF said:

Re Moles vs Echs

 

i was thinking more of questions like: if Echs squared = 32.9 what is the reciprocal of Echs divided by Pi.

 

Below is a photo of how the parents let themselves out of our rabbit proof fence after spending a night on the ant.

Argh! I feel myself being drawn into the Echidna warren of varnish experimentation! 

I have looked at the old book again and on re-reading I wonder if the "deep reddish coloured" drying oyl John Smith mentions as being "before recited" is in fact the linseed oil litharge of lead mixture he refers to before mentioning the copperas driers? Here are the relevant pages in full

 

 

 

Also, after re-looking at my copies of Sir Charles Lock Eastlake's "Methods & Materials of Painting ...."  I suspect the "Copperas" john Smith may be using to help his colours dry may be White Copperas ie Zinc Sulphate (White vitriol)

I have ordered some Ferrous sulphate so I will experiment a bit with it and see how it goes! You never know I may get something worth having ? It is nearly the barbecue season here in England - I will put my fire shovel to the test!

But being so slow at getting anything done, I need to quickly escape the sticky downward pull into the vortex of 'varnish temptation', fun, fascination and experimentation before it is too late and return to my more woodworking related time wasting, which is my main interest really!

[Steve Voigt]

My two pennies, for what it’s worth….

the amounts of iron salts suggested in this thread are grossly excessive. There is a big difference between adding iron salt to molten rosin, and incorporating it into a precipitated rosinate as @JacksonMaberry does. 

I suggest skipping the iron sulfate and investing in a one liter cast iron saucepan with lid. You want to use it unseasoned but clean, no surface rust. Cook your rosin in it. The handful of milligrams it imparts to the resin is all you need….

Moles: Not needed for ordinary cooking, but invaluable if you are doing any kind of precipitation reaction (lakes, rosinates, oleates).

[Steve Voigt]

5 hours ago, Andrew tkinson said:

 

But being so slow at getting anything done, I need to quickly escape the sticky downward pull into the vortex of 'varnish temptation', fun, fascination and experimentation before it is too late and return to my more woodworking related time wasting, which is my main interest really!

I feel your pain.  

[JacksonMaberry]

21 hours ago, LCF said:

Brewing that up with resin, Jackson M would probably say it makes metal rosinates. Chemically speaking it might be similar to liming although the pH is different. It is similar in that somehow a divalent or trivalent atom ( iron, zinc, copper, lime, aluminium, calcium etc) is forming a complex with two or more resin molecules (or oil, or both). Iron and zinc both have some drying action btw. 

Liming rosin is, in fact, making a fused calcium rosinate, as we've discussed. Using a salt of a different metal would be the same - fused rosinate.

Doing it with oil you're making a fused linoleate, or at least trying to. 

[Andrew tkinson]

41 minutes ago, Steve Voigt said:

My two pennies, for what it’s worth….

the amounts of iron salts suggested in this thread are grossly excessive. There is a big difference between adding iron salt to molten rosin, and incorporating it into a precipitated rosinate as @JacksonMaberry does. 

I suggest skipping the iron sulfate and investing in a one liter cast iron saucepan with lid. You want to use it unseasoned but clean, no surface rust. Cook your rosin in it. The handful of milligrams it imparts to the resin is all you need….

Moles: Not needed for ordinary cooking, but invaluable if you are doing any kind of precipitation reaction (lakes, rosinates, oleates).

Hello Steve, thanks for the advice. I have a large old cast iron sauce pan (about 1 1/2 to 2 litres) that I  got very cheaply many years ago. I haven't cooked in it for years as it seemed to add a rust flavour to anything with tomatoes which was not too pleasant to me. (I probably wasn't seasoning it correctly).

I need to concentrate on completing my instruments so I have something to actually varnish but will try a few outdoor varnish cooking attempts over the summer.

As a matter of interest what do you think made the "deep reddish" drying oil mentioned in John Smith's old book, was it the boiled up and burned linseed oil and litharge or the linseed oil and copperas (either zinc or ferrous sulphate)?

All this talk of cooking, cast iron pots and moles made me think of William Buckland

[Matthew_Graesch]

This has been a fascinating read.  I don't have much to contribute from the perspective of varnish, but I do often run across mentions of various sorts of copperas in my collection of 19th century geological texts.  Copperas is apparently one of the common names that was used for various metal sulfides when describing field observations of mineral precipitates, normally emanating from Carboniferous sandstones.  We even have one sandstone stratum here in the midcontinent (US) that was long known as "the copperas beds" prior to the advent of modern stratigraphy.

Fascinating stuff all around.

[LCF]

 

14 hours ago, Andrew tkinson said:

But being so slow at getting anything done, I need to quickly escape the sticky downward pull into the vortex of 'varnish temptation', fun, fascination and experimentation before it is too late and return to my more woodworking related time wasting, which is my main interest really!

You do not want to come to a sticky end with your varnishes but anything that turns into a gloopy mess can be used to make workshop flypaper which also traps mosquitos.

 

9 hours ago, Steve Voigt said:

My two pennies, for what it’s worth….

the amounts of iron salts suggested in this thread are grossly excessive. There is a big difference between adding iron salt to molten rosin, and incorporating it into a precipitated rosinate as @JacksonMaberry does. 

If it does combine to make a rosinate I can't really determine a difference. I don't think Jackson is actually using iron but neither do I think that all of the sulphate combines and what doesn't combine drops to the bottom.  In a zinc or iron rosinate varnish the metal is 100% combined with all of the resin molecules. It us ubiquitous. 'Combined' actually means 'coordinated' from my research eg zinc rosinate typically has a complex of one zinc++ ion  associated with 3 rosinate-. 

My recipes used to be at least 50/50 iron vs zinc and there was always some left over to filter out. 

 

9 hours ago, Steve Voigt said:

I suggest skipping the iron sulfate and investing in a one liter cast iron saucepan with lid. You want to use it unseasoned but clean, no surface rust. Cook your rosin in it.

 

I think that is a goodish idea. Also if you use a stainless vessel, you can some large clean iron pieces in there, or zinc, or tin, or aluminium. I used to cook in an enamelled pot btw. 

 

I am also apprehensive about excessive iron. We knew even then  it might be a problem. The mythology of it has been around for a long time.  I recall the Fulton(?) technique of adding steel wool to the brew. Hot varnish just gobbles that up. Steel wool is very reactive! The colour was originally a pleasant yellow  but the result over time was that classic browned tomato soup colour.

 

9 hours ago, Steve Voigt said:

Moles: Not needed for ordinary cooking, but invaluable if you are doing any kind of precipitation reaction (lakes, rosinates, oleates).

It is still useful to have an idea of what's sloshing around in there. Recipes are important!

 

Also later on I will update these pics but here is a grainy version of 45 year old clear varnish cooked this way and splashed onto fresh maple. The maple itself has yellowed underneath. The varnish has gone towards what most other varnishes that old will do.

Second pic a markie lion scroll with a redder version. This had more iron from sulfate plus some red earth sitting in the pot. 

Neither are black.

 

Edited April 30 by LCF
Corrections, and more corrections

[JacksonMaberry]

At this point I'm not sure what is even being discussed or argued in this thread. 

I don't have anything valuable to contribute to a discussion about throwing handfuls of metal salts into hot resin, oil, or varnish. I think doing any of those things is a fools errand, despite how fashionable they have become of late. 

There will be regrets as the decades wear on. 

[Steve Voigt]

2 hours ago, LCF said:

 

If it does combine to make a rosinate I can't really determine a difference. I don't think Jackson is actually using iron but neither do I think that all of the sulphate combines and what doesn't combine drops to the bottom.  In a zinc or iron rosinate varnish the metal is 100% combined with all of the resin molecules. It us ubiquitous. 'Combined' actually means 'coordinated' from my research eg zinc rosinate typically has a complex of 3 rosin associated with 2 abietates. (I might need to edit those numbers when I find that paper). 

 

Zinc is divalent. So is calcium. They both combine in the ratio of 1 mole metal to 2 moles rosin acids. Aluminum is trivalent, so 1 mole aluminum to 3 moles rosin acids. If there is a metal in the universe that combines in the ratio 2:3, I haven't met it. Actually, I'm quite sure that's impossible with ionic bonds.

Anyway, my point, which I think you agree with, is that the fusion method can lead to uncombined (that is, suspended) metal, which may (or may not) do unpredictable things. Iron is probably the least predictable at all metals, because even a PhD chemist can't tell you what will cause it to flip from ferrous to ferric (or the other way) in the chaotic, unpredictable environment that is a varnish pot. So, I don't use it. Except, as I said before, in the tiny quantities that leach out from a cast iron pot…

[Steve Voigt]

15 minutes ago, JacksonMaberry said:

At this point I'm not sure what is even being discussed or argued in this thread. 

I don't have anything valuable to contribute to a discussion about throwing handfuls of metal salts into hot resin, oil, or varnish. I think doing any of those things is a fools errand, despite how fashionable they have become of late. 

There will be regrets as the decades wear on. 

I'm gonna start calling you grumpy pants!

I think we shouldn't lump all fusion methods together. There's a world of difference between adding small amounts of lime, and adding huge amounts of sulfates or chlorides (which, as you say, has become fashionable!). Varnish makers have been adding oxides, hydroxides, and acetates to to the pot for centuries…there's a track record. Sulfates and chlorides, not so much. 

[JacksonMaberry]

Just now, Steve Voigt said:

I'm gonna start calling you grumpy pants!

I think we shouldn't lump all fusion methods together. There's a world of difference between adding small amounts of lime, and adding huge amounts of sulfates or chlorides (which, as you say, has become fashionable!). Varnish makers have been adding oxides, hydroxides, and acetates to to the pot for centuries…there's a track record. Sulfates and chlorides, not so much. 

Oh, no don't get me wrong, I agree with you fully on this. Like anything else (including precipitation rosinate) one can do it right or wrong.