Linseed Oil Drying

[TimRobinson]

Following on from the discussions about Mr Darnton's mastic varnish and drying times I thought I'd do a bit of a test before making up my next batch. I put drops of four different types of oil on a length of clear perspex 9 days ago. The have not been exposed to strong sunlight for all that time, but have been in semi shade for most of it. The oils:

Artist grade refined linseed

Cold pressed extra virgin flaxseed (the one I used in my first batch of varnsih which refuses to dry)

20 year old virgin linseed oil

Boiled linseed oil - hardware store variety.

The result? They are pretty much the same, however I would say that the artist grade refined oil and the 20 year old virgin linseed oil have dried harder than the other 2.

Next step is to mix each with the turps/mastic mixture and put each on some prepared (vernice bianca) timber and see what happens.

Regards,

Tim

[Michael Darnton]

I wonder if the problem is either too much or too little oil in the mix. Mastic by itself is very soft, and doesn't release solvents too well, so either scenario is plausible.

[HongDa]

I have also just tested 2 linseed oils for drying properties.

First, Windsor Newton Sun Bleached linseed oil, which I used in my first few batches. These batches will not dry to a firm thumb print test even after adjusting the amount of oil from anywhere between 25~40%.

The second oil is Windsor Newton cold pressed raw linseed oil. I will try this with mastic and turpentine in a few days.

Both of these oils dry on their own under UV light. However the sunbleached type dries much faster than the cold pressed.

From this experiment so far it looks like changing oils will not help unless for some reason the coldpressed oil has a different reaction on drying/stabalizing the mastic then the sunbleached oil. If that's the case then I guess it's either my mastic or more humid/hot weather that are the culprit in my drying problem.

I know Michael, and I think most others mention the mastic taking 2 weeks to disolve. Mine only takes about 5 days with a few shakes each day. Does anyone know if this means my mastic is bad? I got it from Hammerl in Germany.

Thanks for sharing your experiment results.I'll watch this post and also let you know what happens with the 2 oils I am using.

[Craig Tucker]

My mastic, from Chios, also dissolved in about five days. (maybe less)

[HongDa]

ok. And from what I have read nobody is having trouble with the Chios mastic, so 5 days doesn't seem to mean there is a problem.

If you press your finger very firmly against the varnish for a minute or more does it print at all?

[Michael Darnton]

I'm not sure we do have positive confirmation that no one's having trouble with the Chios mastic. Can anyone who's used it say something about it?

I used mastic from Kremer, and oil from Utrecht.

[Craig Tucker]

Yes, I have used it (Chios Mastic) and my mastic varnish has dried well.

[Andres Sender]

Chios mastic, Utrecht linseed oil, dried fine.

[HongDa]

Quote:

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I'm not sure we do have positive confirmation that no one's having trouble with the Chios mastic. Can anyone who's used it say something about it?

I used mastic from Kremer, and oil from Utrecht.

---

I think only a few of us are having trouble with drying.

I now have about 120 grams of mastic invested in varnish that I'm not sure what to do with now,---quite frustrating.

Today I will try modifying some of it with a recipe from the Hammerl book by hopefully dissolving Manila copal and sandarac in turpentine and adding that.

I'd also be curious to know what the temperature and humidity is like for those who are having trouble with drying.Or if any of those that aren't having trouble live in a humid and hot climate. I beleive Yap down in Malaysia is having trouble also but not sure if that is to do with his experiments using eucalyptes oil instead of turpentine.

Also I wonder if anyone else has been fooled into believing the varnish is dry/stable as I was in the beginning.

To be really sure about it I have found it needs very firm fingertip pressure for about a minute or more.If the weather is cold it may take longer.

[TimRobinson]

Quote:

"I'd also be curious to know what the temperature and humidity is like for those who are having trouble with drying.Or if any of those that aren't having trouble live in a humid and hot climate. "

For humidity and heat try Sydney in late summer :-)

Seriously, my experience has spread across spring, summer and now early autumn. This covers temperatures from about 10 to 40 celsius and RH from about 35 to 100%.

Regards,

Tim

[HongDa]

I take this to mean you aren't having any drying problems?

Can I ask what mastic you are using?

Does anyone here happen to be using Hammerl mastic?

Maybe this is my problem.

[TimRobinson]

No, I am having drying problems, that's why I'm doing the tests with the oil to try to establish where the problem lies. I do not think it has much to do with temperature or RH - at least not the Sydney climate. If it were very cold and we got no sunshine I wouldn't be surprised if I had problems with drying, but this is Sydney, it is sunny and warm here

The mastic is from Chios.

Regards,

Tim

[HongDa]

Quote:

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No, I am having drying problems, that's why I'm doing the tests with the oil to try to establish where the problem lies.

---

So we are having the same problem.

I'll post my results on here as they come in. But so far doesn't look promising.

And da#n the Hammerl book!

How's this for a contradiction?

Boil 2 parts turpentine, 1 part venetian turpentine, 1 part each pulverized copal (manila or kauri)and sandarac in a water bath until dissolved.Then add boiled linseed oil.

(This is their recipe for an oil varnish. I was hoping to get some copal or sandarac into the mastic varnish I have now in order to save it.

So far all I have is a messy clump of the above resins )

Then going back into the book on individual resins it states that copal is not soluable in turpentine.

Doesn't mention what sandarac is disolved in.

And says venetian turpentine should never exceed 3-5% of the varnish.

Must be German humor.

I find this book full of many such contradictions so I guess I deserve what I got with this experiment

.

[Wolfjk]

Hi S_H,

Perhaps linseed oil is not a drying agent at all but helps the varnish to be flexible. In window glazing we put linseed oil in to stop the putty from drying up.

So perhaps the amount of oil one adds to the varnish is critical to the drying time.

Cheers Wolfjk

[joerobson]

LInseed oil needs to be tested before making any varnish. Primarily because if flax, the source for linseed oil, is grown in rotation with rape seed, the source for canola oil, the linseed oil will not dry. Temperature and exposure to light make a large difference.

When linseed oil is exposed to the proper conditions of heat and available oxygen it begins to absorb oxygen at a rate that builds to a peak and then rapidly diminishes. The early rapid absorption of oxygen is known as the period of induction. At ordinary temperature clarified raw oil will have an induction period of 1 – 3 days. When exposed to the right conditions of oxygen and temperature, in a thin film, the oil will form a clear, hard solid in a rapid manner. In the induction phase little or no weight is added to the oil. Chemically the initial reaction in the oil is the formation of an organic peroxide which acts as a transitional material to build the rate of absorption to a pace that allows the oil to absorb and hold oxygen. The function of the catalyst (pre-treatment of the oil, metallic driers, or exposure to ultraviolet light) is to rapidly create these peroxides. Metallic driers virtually eliminate the period of induction; which tends to create a varnish film which is hard on the outside and soft underneath. Pre-treatment of the oil will produce a varnish film which cures at the same rate throughout its thickness. The curing of the film is directly effected by light. (If two samples of raw linseed oil are taken from the same press batch and spread on photographic plates, in films of equal thickness, the comparison between curing them in the dark and curing them in the light is dramatic. The film placed in diffuse daylight will achieve initial set in 1 – 3 days, be tacky in 3 – 5 days, and achieve tack-free dryness in 6 – 9 days. The film place in the dark, at the same temperature and atmospheric conditions, having all measurements done under red light, will reach initial set in 20 – 22 days and tack-free dryness in 65 – 68 days.) At the end of this process the oil will have gained almost 30% in weight and lost 12 – 15% in volume.

[yapkv]

From the book "The Violin Explained" by James Beament page 188- 190:

"... plant oils and animal fats consist of three long non-polar paraffin chains attached to a stem of 3 carbons. the chains differ in length according to plaint or animail species.."

Code:

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c-chain

|

chain-c

|

c-chain

---

"two of the three chains of linseed oil each have two place where adjacent carbons have only one hydrogen. These place 'want to be saturated' "

two of the three linseed chain:

Code:

---

O

|| H H H H H H

- O - C - C - C - C (=) C - C - C (=) C - C - ......

H H H * H H * H

---

now imagine: when two molecules of linseed oil comes together,

Code:

---

chain1-c

c-chain1 c-chain2

chain1-c chain2-c

c-chain2

---

with the present of oxygen, the "want to be saturated carbon " joins together through one or two oxygen,

Code:

---

(chain1) C - C - C - C - C - C - C ....

|

O

|

(chain2) C - C - C -C - C - C - C....

"Then the chains can slowly join directly"

..C - C - C - C - C - C ...

|

.. C - C - C - C - C - C....

---

hence the polymerization process, forming a gigantic long molecules...

-----------------------------------------

The book also mentioned that due to the need of oxygen to form the joins to for of the polymerization process, it is important to apply the varnish as thin as possible.

"six thin coats dry faster than two thick coats."

In addition to that, the author also mentioned that "cold-pressed" linseed oil contains about 10% of lecithin, which is polar, and used to tranport linseed oil to other parts of the plant. it can be seperated with gentle heat -> the resulting oil is then known as "raw" oil.

----------------------------------------------------

From

http://www.ibiblio.org/herbmed/eclectic/ki...tacia-lent.html

"Chemical Composition.—Mastic contains 2 per cent of an essential oil; according to Flückiger, it is dextro-rotatory and chiefly composed of a terpene (C10H16), boiling from 155° to 160° C. (311° to 320° F.). The principal constituent of mastic is a resin which was differentiated by Johnston (Phil. Trans. 1839) into alcohol-soluble alpha-resin (mastichic acid), about 80 per cent, and alcohol-insoluble beta-resin (masticin), the latter being tough and elastic, soluble in ether and in absolute alcohol, also in alcoholic solution of mastichic acid. According to E. Reichardt (Archiv der Pharm., 1888, p. 158), benzin effects the differentiation of mastic resin more readily and more completely than alcohol. Old mastic yielded to benzin 66 per cent, while new mastic yielded 90 per cent. Analysis showed that the insoluble resin is formed by the gradual oxidation of the soluble portion. Mastic also contains a bitter principle, soluble in boiling water; it is precipitated by solutions of tannic acid."

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with the above information collected from different sources and inputs from everyone in the forums, I am guesing that s a good Darnton varnish will dry properly under the following condition:-

1. The mastic must be "fresh". (old mastic would have insoluble solid)

2. Gentle heating of the oil "may" required if coldpressed oil is used (before adding this to the mastic-turpentine solution).

3. Oxygen, oxygen, oxygen (since both mastic and linseed oil needs oxygen to form solids.) Bubbling the linseed oil before mixing them into the mastic-turpentine solution?

4. Sunlights to catalyse the process

5. Hongda: I think we both need to get a dehumilitifier or tons of silicon gel... (water molecules condense on the varnish surface may hinder the oxygen from forming the -c-o-o-c bonds)

Can someone comment about this?

[Regis]

Now that was on the tip of my toung but I just couldn't type it fast enough

[Wolfjk]

Hi JoeRobson,

Thanks for your post. It is nice to have an expert on varnish helping out.

Perhaps the simple questions are: what proportion of linseed oil should we add to a saturated solution of mastic-in-turpentine? Should the linseed oil be boiled, raw or cold pressed ?

While I agree that a thin film of linseed oil dries quick enough, too much of it might inhibit a thicker layer of varnish from drying.

Cheers Wolfjk

[HongDa]

Quote:

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with the above information collected from different sources and inputs from everyone in the forums, I am guesing that a good Darnton varnish will dry properly under the following condition:-

5. Hongda: I think we both need to get a dehumilitifier or tons of silicon gel... (water molecules condense on the varnish surface may hinder the oxygen from forming the -c-o-o-c bonds)

---

Yap,

I enjoy reading the technical reports on varnish but find they can also just make things much more complicated.

What I really look at here is that most people on the board are not having problems and as far as I can figure out I am doing it just the same as them--only I have been using sunbleached oil.

As far as humidity……………., I now doubt that is my problem because I do have my instrument in a box with 4 lights which creates a pretty dry environment.

I'm still waiting for my new batch of mastic to settle and will mix that with coldpressed oil and see what happens with it. Hopefully it will solve the problem.

The other thing I am working on is the batch I already made with a lot of mastic invested that won't dry correctly. This is the batch with sunbleached oil. I have taken small amounts of it and experimented----more oil, dryer, covering with dilute shellac----none solved the problem. Next step is to try mixing copal and sandarac in it. Which by the way I did finally get it to dissolve by adding a little alcohol

[Michael Darnton]

The only thing I can think of is that the person who told me the trick of using no heat in dissolving the mastic said it wouldn't dry hard with heat. Is it warm where you folks are?

[HongDa]

Quote:

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The only thing I can think of is that the person who told me the trick of using no heat in dissolving the mastic said it wouldn't dry hard with heat. Is it warm where you folks are?

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Michael,

My first batches were made when the weather was cool enough to require a jacket. So I don't think that is it.

However the other 3 having problems--Amori, Yap and Sir Hilary are in the southern hemisphere--so maybe their problem is something to do with the rotation of the earth! In particular, everything in Australia goes backwards so maybe Sir Hilary just needs to make his varnish backwards .

Seriously though, I think I see what you are getting at in your reply and happen to have another side experiment going on. I noticed that when I dissolve my mastic in alcohol for shellac varnish there is also residue or dregs in the bottom as when dissolving mastic with turpentine. I found that the residue left over from an alcohol dilution can be further dissolved by adding turpentine(quite a lot) but not vice versa. This must mean that turpentine dissolves something more in the mastic which alcohol doesn't. (Yap happens to have made a post above concerning the makeup of mastic and how it dissolves. My experiment appears to work against this but I'll continue with it nevertheless).

What I'm hoping to find, is that if I first dissolve the mastic in alcohol, let that evaporate, and THEN add the turpentine --it will for some reason be more stable.

However, even if I'm lucky and it does work--it still doesn’t explain why this varnish is working for most others on this board but not the rest of us.

Do you have any comments on adding copal and sandarac?

Also, what type of linseed oil are you using exactly?

[yapkv]

Hi Hongda

well, in fact I am staying just 6 deg north of the Equator. Yes, it is really hot and humid here ( 30~32 deg celcuis in the daytime)

More information about oil...

http://www.cad-red.com/mt2/oil.html

from the information gathered, oxygen is definately the very important factor to get the oil to dry. perhaps we should add some fans to our UV light box....

flipping through the book written by Juliet Barker, she mentioned in her varnish chapter that, the UV light box should have a thermostat set no higher than 22 deg celcuis. I believe there must be a reason for her to say tha. i guess i can only get such condition in an air-conditioned room. however makes me wonder how the old master in Cremona get their varnish dry... isnt' that Cremona hot and dry?

my only source of mastic here is from the chinese traditional medicine shops and they don't dissolve well in artist turpentine... i guess i would just stick to damar-oil varnish as suggested by Michael in his previous post. I can get damar here easily - it's used by natives here to dye clothes. the only thing about damar varnish is that they tend to be too glossy.

Yap

[TimRobinson]

My first batch was commenced in our winter, cool but never below 4 or 5 celsius. The second lot was commenced a few weeks ago doesn't have the oil in it yet, has been in temperatures ranging from 13 to 27 C.

Over the weekend I made some small samples up with each of the oils I have (see earlier post) and have left them in sunlight. We'll see what happens now :-)

Just a thought I had while doing this - what ground have others been using. Could vernice bianca be reacting in some way with the varnish?

Tim

[Michael Darnton]

I've used in on top of a number of things, but not vernice bianca.

[HongDa]

Yap,my oil tests show no problem in drying the oils themselves on a glass strip in the uv box.

It's only when I have the varnish mixed that I then have the drying problems.

I do seem to be having some luck with putting copal into the varnish and getting it to dry now!!

Too early to be sure yet and I want to put a few more coats on the test strip before getting excited.

I believe alot of traditional oil varnishes use mastic, copal and sometimes even sandarac cooked with linseed oil.

If the same ingredients can be used under Michael's "cold" method then this may possibly solve the problems we are having.