Linseed paint

[blackleafforge]

I am working on a sculpture at the moment and followed the advice of a few smiths to get it hot zinc sprayed then etched then painted for the best exterior finish. I naively was a little surprised at the cost (£300 for a tree sitting on a base, aprox 1 meters square). My client has asked for alternatives so I started looking in to it and a traditional proven finish of linseed paint sprung to mind. I am however slightly suspicious of the fact that it does not seem to be widely used by the modern blacksmith community. I rang up one of the few uk suppliers to ask about longevity and application and her claims seemed to be a little to good to be true. She said the the finish would last indefinitely and would just dull very slightly after 10 - 15 years. She also said it had a good degree of flex so would not crack or flake off with thermal expansion and contraction of the metal. 

Has anyone else used this system? what are your thoughts? 

Thanks

Andy 

[SLAG]

Slag Here,

Scientists have very recently discovered that linseed oil varnishes (covering paintings) does not protect them from moisture. In fact linseed oil is hygroscopic. That is, it draws moisture out of the air and into the varnish surface! I am not suggesting that linseed oil paints would have have that problem. I am talking about the varnish that is used for coating the dried paint surface, in order to protect it from the air. (e.g. water vapor, air pollutants, SO2 & grime).

I suspect that a lot of oil paintings will soon have their varnish stripped off and new varnish applied. (without linseed oil).

SLAG.

Edited May 23, 2016 by SLAG
clarificationing

[Steve Sells]

I dont understand why zinc coat it then etch ?   .l would think the etching process would remove the zinc plating ?

[ThomasPowers]

etching the zinc makes finish adhere to it better and is a common step for outdoor items; they even make etching primers for such.

It's not etched so much that the zinc is totally removed.   Not used in knifemaking world that I have ever heard of!

[Steve Sells]

I admit I was thinking of etching as in Sand blasting or Parkerizing, not just a  light roughing of surface.. thanks TP...

[gote]

17 hours ago, SLAG said:

I suspect that a lot of oil paintings will soon have their varnish stripped off and new varnish applied. (without linseed oil).

SLAG.

It has been used on paintings for a few centuries and nobody noted any deterioration of the underlying paint.  What does happen to old paintings is that the warnish becomes grimy and darkens so it makes sense to strip it off - which is a delicate operation done by specialists. I would be interested to see the original research. Organic materials such as canvas and wood used below the paint are much more hygroscopic and permeable to moisture than paint or warnish. 

The Swedish army told me that "If map and terrain do not agree,  Terrain is right." It seems that in this case, the map needs warnishing .

Presently lineseed oil is touted by environmentalists to a degree that I think is exaggerated. In test on uncoated steel, pure linseed oil has not been as efficient as modern rust protecting materials. Traditionally it has been used in lead based paints (no longer allowed) to stop rusting. The result depends s lot on the location. relative humidity, possible salt spray from the sea or deicing etc etc. My father used linseed based paints on barn hinges and the like and they are OK half a century later but I do not know which possible inibitors that were used.

 

 

[SLAG]

Because most paintings have not had problems does not preclude potential vulnerability of some artwork to moisture in the air. . Linseed oil__ varnished__ art may not always be immune. Very humid climates could jeopardize such paintings. Indeed. the majority of museums, art galleries, auction houses, etc., have strict climate control and will not experience moisture varnish problems. The potential damage would be very slow.(as it has not been noticed 600+ years until now). An interesting case was encountered with the pigment Prussian blue. That pigment was used in oil paints for two hundred years + (1704 Diesbach). Under certain ambient conditions the blue color turns black. The majority of paintings have never experienced this problem. But a minority of artwork did. The culprit was minute amounts of sulfur dioxide in the air. The color was still used until just recently because blue pigments are rare. (it has now been replaced with French ultramarine (synthetic lapis lazuli),, cobalt blue and phthalocyanine blue.). Likewise, cadmium yellow's permanence has just recently come into question. That color has been used, extensively, since 1820 and was thought to be permanent. (and in most cases it is).

One point should be stressed. I am discussing only the use of linseed oil as a varnish.  I tried to make the distinction between the use of linseed oil as a vehicle for colors (oil paint)and as a varnish. Obviously I was not clear enough. There seems to be no problems with linseed oil based paints. Their first use dates back to 1410 and no problems have ever been seen.

I will search for the reference that reports linseed oil as being hygroscopic, and get back to you.

Another point, is the base of oil paintings such as wood and canvas is coated with gesso before paint is applied. (canvas also is coated with rabbit skin glue).The gesso has lead carbonate as a constituent. In other words that coating protects the base from air and moisture. (the paint colors are applied over the glue and gesso base).

Gote thanks for your comments. It pointed out that my original comments were not clear enough.

Regards,    SLAG.

Edited May 24, 2016 by SLAG
further clarification

[LawnJockey]

I used pure boiled linseed oil on a brazed steel bicycle frame about 6 months ago and it seems to be holding up well and it is stored in a car port.  It took weeks for it to set up so that is something to think about.  I understand that some linseed oil products inclued an accelerator to speed up the "drying" process.  If you use something that takes forever to dry you have to worry about dust settling on the surface.

A few years back I used a three step system sold by Sherrwin Willams and I am sure by others.  First we cleaned the new galvanized sheet metal with acetone.  Then we used their etcher followed by their primer and then the top coat.  It still looks like new after constant exposure to the elements including snow and temps up to 118F.

Back in the late '80s I did an osmotic blister job on a fiberglass (FRP for you guys in the UK) sailboat with a cast iron keel.  After all the sanding we wiped everything down with acetone.  Then we treated the exposed cast iron with Ospho.  Then we painted the entire underwater surface with Zspar 646 epoxy primer followed by anti fouling paint.  A few years later I saw that boat out of the water and there was a section on the cast iron that had the antifouling sanded off, the 646 beneath was in perfect condition.  That boat had been in salt water the entire time in marinas with lots of electrolysis issues too.  I am not sure 646 is still marketed under that name as there has been a lot of consolidation in the marine coatings industry.  If you use one of these epoxy products make sure you follow the safety instructions completely as the fumes cause brain damage quickly.  Also make sure other unmasked people are not around.  I have gotten a nasty headache from being over 100 yards away from a job where 646 was being used.

If you go the epoxy coating route here is a tip not many know, tool and hand clean up can often be done using white wine vinegar rather than acetone.  It is a lot cheaper and more healthy for you too.  

 

[SLAG]

Artist supply stores sell accelerating drying agents for artists'  oil paints. They are called siccatives.

SLAG.

[gote]

Obviously I was unclear myself. I tried to treat artist's varnish first and the use of linseed oil based tratments for outdoor use on steel afterwards.

You are right. I have found a reliable reference. Hardened linseed oil is slightly hygroscopic. Incidently this is the reason for the limited protection when used alone one on steel. The Swedish department of antiquities Riksantikvarieämbetet has issued interesting reports on the subject - in Swedish. Thank you for making me reading it up.

However this does not make the varnish a problem for the underlying paint in art work since moisture in itself does not deteriorate the paint. Linseed oil based paints have been used traditionally outdoors on wooden buildings.

The main reason for warnishing paintings was not to protect the surface. Artist's paints are heavy on pigment and when the oil hardens the surface may become matte because the oil "sinks in". The warnish will restore the glossy surface

Several kinds of pigments deteriorate but rarely from moisture.

The gesso is used to prevent the linseed oil from attacking the canvas. (And to give a good surface to paint on) That does not mean that it is impervious to moisture. Animal glue will eventually dissolve in water and lead carbonate will not prevent movement of moisture.

[SLAG]

Retouch varnish is often used by oil painters after and even during painting. (of course other varnishes are used for completed artwork. Even). Even cadmium yellow can deteriorate after contact with polluted air. One of the most active paint destroyers is sulfur dioxide. Varnish serves as a shield for that. (CO2 is also a problem). Also grime. The study of archival chemistry is fascinating also fugitive pigments, & paper deterioration. ( Chemical & Engineering News, of the American Chemical Society has had some very interesting feature articles in previous years.) The National Gallery of Canada has done stellar work in this area. They publish bulletins regularly. (I'm certain they're on the net.). Sadly, I do not read Swedish but they probably have published in English Language journals. 

Regards,

SLAG.

P.S. The date of first use of oil paint art work, is 650 A.D. & not 1410. 1410 is the date for first use of canvas as a base. (previously, wooden panels were used,. I got the dates mixed up.

Edited May 26, 2016 by SLAG
more gem s added

[ThomasPowers]

I've seen more than one discussion of "black armour" based on certain illuminations that come to a screeching halt when you point out that they were originally done with silver leaf and were shining silver---the black is due to 400+ years of aging

[SLAG]

I remember my mother and grandmother regularly & tediously polishing the tarnish off their sterling silver. Most of the tarnish was caused by sulfur in the air. (SO2). Cooking Brassica vegetables (Brussel sprouts, cabbage, cauliflower & etc. gives off hydrogen sulfide) and it eventually lands on, and reacts with silver. Another source of that gas was coal fire fumes that a tiny % could pollute the indoor air Coal heating was used, long ago, for the space heating of houses during fall and winter. Tarnish, was a good reason why I prefer stainless cutlery over silver.

SLAG.

[SLAG]

Gote

Check out the latest issue of chemical & Engineering News: May 23, 2016. p. 21-23. It has a fascinating three pages on a new scourge for painting conservationists. Namely erupting metallic soaps.

Regards SLAG.

[gote]

On 2016-05-26 at 5:30 PM, ThomasPowers said:

I've seen more than one discussion of "black armour" based on certain illuminations that come to a screeching halt when you point out that they were originally done with silver leaf and were shining silver---the black is due to 400+ years of aging

Yes that is an interesting observation. Silver can be quite black as in niello. Do you know how the silver leaf was put onto the steel? Glueing?? I have some gold leaf lying around and I would be interested if I could fix it onto steel rather than gesso,

On 2016-05-27 at 2:56 AM, SLAG said:

Gote

Check out the latest issue of chemical & Engineering News: May 23, 2016. p. 21-23. It has a fascinating three pages on a new scourge for painting conservationists. Namely erupting metallic soaps.

Regards SLAG.

Will try to Thanks.

[SLAG]

Gote,

Silver becomes black because the surface reacts with sulfides in the air. The silver forms black silver sulfide. Minute quantities of sulfides are ubiquitous. Cooking brassica vegetables puts a lot of SO2 into the air. For example cabbage, brussels sprouts, broccoli etc. all have generous amounts of the sulfur containing amino acids. (cysteine methionine, etc.) The gas is common in industrial town air.Gold does not react with air borne sulfides. The metal is almost inert. (viz. long submerged gold coins, found in ancient shipwrecks, look as good as when they were first minted). Your gold leaf works should do fine.

I will ask Marg to help me to e-mail the article to you. The last time I tried, the computer took a chomp out of my hind, end and my Internet service provider sent me a cease & desist letter.

My ego is still in recovery.

Regards,

SLAG.

Oops I already said that in a prior post. Sorrry.

Saliva is sometimes used to help gold leaf to adhere to surfaces. Check mister Google for details. Yah  our spit.

Bonne chance,

 

SLAG.

Edited June 25, 2016 by SLAG
apology given