What about Damar?

[Stophel]

What about damar for varnishes?  The dealers often recommend Damar for a good all around varnish resin that is easy to use.  Is it good stuff or not, and was it used in the 18th century?

[Mad Monk]

Well you sure answered that one for me.

In the other thread the subject of resins was discussed.  I was debating if I wanted to get into it deeper or just walk away.  Your question answered that.

A bit of background here.
My 37 years experience in synthetic polymer production was in production, QC and R&D.  One of my specialities was PVC solution resins or PVC copolymer resins used in solution work.  As PVC kitchen flooring replaced linoleum which replaced oiled florr cloths the solution resins I worked with replaced shellac and many of the natural resin solution coatings.  The R&D library had a host of books on the subject of paint and varnishes.  Some dating back to the 1920's and 1930's before the man-made resins replaced the natural resins.

As it relates to varnish manufacture.

They classified the natural resins into two general classifications.  Those being "fresh tapped" and then "fossil" resins.

Generally. Fresh tapped resins were cheap and used in cheaper grades of varnish.  The fossil resins were of course more expensive and used in the more costly varnishes were durability was one of the main criteria.
Damar resins are in the fresh tapped class.  The damar resins are produced in Souteast asia.  Two best known were Batavia and Singapore damars.

These damar resins were used in cheap factory varnishes.  This is the resin generally used in the varnish used on old oak factory furniture in the early 1900's.  These varnishes were noted for cracking in the pattern called alligatoring.

On the other hand the more expensive copal resins were used in carriage varnishes where they would see all sorts of weather.  The damar varnishes simply could not survive outdoors the way a copal varnish did.

Some cheap hardware store varnishes were made with modified rosin.  The rosin would be melted and treated with a little lime.  Rosin being a fresh tapped resin.

What made the copal resin varnishes more expensive than the fresh tapped resin varnish involved how it had to be processed, heat run, to make it soluble in the boiled oil.  Some varnish manufacturers started to use heated vacuum kettles where they would recover the vapors pulled off the resin which was then sold as an essential oil.

Another important point in this.
The varnish books talk about "short oil, medium oil and long oil formulations.  Then give the amount of boiled oil required and amount of resin required for each.  This proportion of resin to oil effects the properties of the dry varnish film.  Straight boiled oil does not truely dry to a hard film.  Technically it is more of a gel.  When a boiled oil film drys it drys to about 90% of its weight when judged by joined molecules.  It may take several years for the other 10% to go through drying.  Then there is a period of time where the film is chemically stable.  Then given certain conditions of exposure the oil film begins to break down and sort of resort back to an oil.

The addition of a natural resin adds toughness to the film in terms of film hardness and film permeability.  The price of that is reduced film elongation on surfaces noted for extensive expansion and contraction, such as on wood.  The harder more brittle varnishes are noted for cracking when the wood is "dinged".

So any time you get into varnish making you are playing with a bunch of trade offs in what you want in the way of properties in the film and what you give up to get those particular properties.

Each of the natural resins had properties different than the others.  These differences came into play in which resin, or resins, were best suited for particular applications.

My view on this relative to gunstocks was what you would want to be seen 100 years down the road.  A great grandson showing off great grandpappys rifle.  Would great grandpappy be remembered as a first rate craftsman or a common hammer mechanic?

E. Ogre

[Stophel]

I think I'll stick with my rosin, mastic, and benzoine!   

So far, I have not seen damar mentioned in 18th century or older varnish recipies.  I often see rosin, mastic (chios tears), copal and sandarac.  I can't do copal or sandarac, which has to be run (melted) separately, and I just don't want to fool with that.  (although some of the old recipies claim you can add sandarac to the boiling oil....They Lie!!!).

[J.D.]

I don't remember sandarac being available in artist paint supplys, but  copal suspended, in what appears to be clear linseed oil, is available at a nearby Micheals.

Not knowing about the chemistry of boiled oil finishes, I don't know how the prepared copal dryers would affect the BLO.

[B Shipman]

Damar is a later varnish. Close to mid 1800's.

[Acer Saccharum]

Damar is not as durable, as I recall, from 'The Artist's Handbook". 

I bought Copal, suspended in Linseed, from Kremer Pigments, along with a jar of siccative(leaded dryer). Wood finished with this varnish is glossy, and the finish not brittle, and seems to be very water resistant. I had a flat piece of wood, finished with copal, and laid a great big drop of water, about the size of a half dollar, for hours, until it had evaporated considerably, and could detect no water damage or discoloration, no swelling of the wood fibers underneath.

Great info, Monk.

[Mad Monk]

Acer,

Going back to the mid 1980's.  A college prof in Texas was looking at Stradivari violin finishes.  In his first news release he commented that the wood had first been treated with a mixture of animal blood and chicken droppings.  Which had me rolling on the floor.  He was looking at a nitrate of iron stain and did not know it.  He judged that from his background in college.

Then about 5 or 6 years later he published a big article in a chemical industry magazine about the varnish used by Stradivari.  Commented on a "lattice structure" with ground up semi-preciuos stones added in.  Given his background that lacked any varnish information he simply identified a classic boiled oil varnish formula where the coats of varnish had been rubbed down with garnet between coats.

The whole idea of adding a resin, natural or man-made, in a varnish is to harden the film and make it less permeable than a straight boiled oil finish.
The density of linseed oil is well below that of water.  Even the dry boiled oil film exhibits a density lower than that of water.  So this makes the boiled oil films fairly permeable.

Now when you add a natural or synthetic resin to raise the density to a level above that of water which decreases the permeability of the film.

When you prepare the varnish it is important that the resin is soluble in the boiled linseed oil.  As the varnish film drys the resin becomes insoluble in the film so the resin precipitates out as very minute particles scattered uniformly throughout the film.  This also acts to decrease varnish film permeability.

When you spread a straight boiled oil film on a surface it will form very minute globules sort of scrunched up together.  I don't know if this is the correct spelling but we called them micells.
Anything dissolved in the oil will become insoluble as the oil forming the globule drys, polymerizes actually.  The spent dryer metal and any resins included are kicked out of the individual micells and end up filling spaces between the individual micells.

When I first read about this I set it up under a powerful microscope in the lab.  Spread oil films on glass slides and then watched how it worked.  If you think watching corn grow in Iowa is fun you ought to watch boiled linssed oil dry under a microscope.  But the chem engineers I worked with thought it was a great teaching tool.

E. Ogre

[NSBrown]

Monk, don't stop. I hate to admit it, but this is actually interesting. Go on.

[Mad Monk]

Something else I should mention here.

The quality of the boiled oil used to make the varnish will help to determine how clear the varnish film is.  If there is a lot of insoluble debris suspended in the oil the varnish film will not look clear and "brilliant" on the wood.  This thing about varnish film "brilliance" refers to how the varnish film transmitts light down to the interface with the wood and then reflects it back up through the film.  This also effects how we see varnish film depth.
I had looked at several real nice Lehigh County rifles in Dixon's collection.  One in particular.  The varnish looked extremely deep and thick.  But where a chip had been taken out of the varnish you could see that the varnish was extremely thin.

For a good "brilliant" varnish the boiled oil should be allowed to sit and self-clarify for a fairly long period of time.  If you cook your own linseed oil and store it in bottles you can see this change in clarity as the old ages (tanks).

Loading up a boiled oil with a lot of lead dryer metal that will eventually be used in the preparation of a varnish is an error.
As the oil micells polymerize (dry) the spent lead dryer metal is kicked out of the micells.  The spent lead is concentrated in the surface region of the dry oil film.  This spend dryer lead may then be exposed to sulfur-bearing gases and form lead sulfide which is black.  You can end up with a varnish film that looks like the "smoked" plastic panels on a stereo.  
You sometimes see original rifles where the surface of the finish, boiled oil or varnish, is black.  With the wood wood figure visible in areas of wear of the finish.  This blackening of the surface, or "patina" is created by sulfur-bearning gases blackening the spent dryer lead in the oil or varnish film.

E. Ogre

[Mad Monk]

When I was buying books on Pennsylvania gunsmiths published by Shumway I noted that a fair number of those old gunsmiths used to also produce stringed musical instruments in addition to their gun work.  The old gunsmiths worked brass much the way the German wind instrument makers worked it.  Then we have gunsmiths also making instruments such as violins.  So it appeared that there was some "commonality" in the skills required for each of these different products.

So I special ordered: Violin - Making as it was and is - by Ed. Heron-Allen.
The 1984 reprint.
ISBN 0 7063 1045 4
Originall published in 1882

Some good information on coloring the wood and varnishes.  A good section on the natural gum resins.

The other day I checked Google to see if it was available as a pdf download.  No deal.  Lots of hits for used copies.
But a good addition to a library


Then some years back Jim Kelly graciously sent me a photo copy of:
A Practical Treatise
on the
Fabrication Pf Volatile And Fat Varnishes,
Lacquers, Siccatives, And Sealing-Waxes.
From The German Of
Erwin Andres,
Manufacturer Of Varnishes And Lacquers,
With Additions On The
Manufacture And Application Of Varnishes,
Stains For Wood, Horn, Ivory, Bone
And Leather

This baby proved to be a gold mine of information on how these things were done in the time period we deal with in our hobby.

So of course I hit Google to see if it was available as a free pdf download.
No deal!!
A lot of hits on used copies floating around.


But for those of you who want to look at "period technology" these two books are good starting points.


E. Ogre