Thread: Fossil Copal Varnish

it's probably not of extreme interest here because I don't expect anyone will take up running varnishes, and especially copals but the congo copal that we can get here is about $65 a pound. So, more than shellac, but not terribly so.

In the mix on this wood, it's somewhere around 1.5 parts linseed oil, 1 part congo copal resin (after some is lost in the run removing impurities and making it oil soluble), and then turpentine and naphtha can be used for thinning. Turps is suggested for finishing the varnish in the cook, and can be used entirely, but for brushing, i'm experimenting with naphtha as the additional thinner at application time because it seems to work well and it costs half as much per gallon as good turpentine costs per quart.

At any rate - the point -there's one retailer in the US selling congo copal for between 80 something and $65 or so depending on how much you get, but the fossil copal that the publications glowed about 150 years ago was zanzibar copal. And that is more widely available, but my comment about that was in terms of how likely it's fraudulent. I'll bet a lot.

The only reputable supplier I can find with stuff that looks right is $148 a pound. it is cleaner than the congo copal and probably easier to run. The magazine publications from 1870 claim that the varnish is even harder from zanzibar despite the lower melting temp. Combination of hardness and toughness makes for an extremely durable surface and one that does not shatter around scratches, so the scratches and surface wear you'd get would be very superficial.

I will probably get a couple of pounds of zanzibar around Christmas just to see what comes of it.

The cost to run and make a varnish out of it that's 70% solids would be about $170 for a quart

But the effective equivalent would be to something like coverage from a half gallon of finish.

The other extremely high durability very stinky and toxic commercial finishes (two part polyurethanes in a can - or really two cans, one for each part) are somewhere around that price. $100 a quart or $325 a gallon.

not exactly suitable for painting fences.

I figure a quart of congo copal is about $80, still not cheap. Thinned to double, about $85 for half a gallon - no more expensive than a lot of things like waterlox and finishes like waterlox (appears to be a phenolic/modified tung oil varnish with a little bit of rosin(processed pine resin)) are good, but they are not close to a copal or amber varnish in quality.

Sh*t, I'm still stuck running rosin and trying to get a usable varnish out of it, I'm falling behind.

The Congo copal sounds like it blows the rosin varnish out of the water, and yet that's what they used back in the day for musical instruments.

How about furniture? what finishes, besides shellac, were used in the 15th, 16th centuries and onward? Perhaps those in the restoration business can offer some context here.

Rafael

not an expert *at all*....but have read that sandarac was very stylish for a couple of hundred years for furniture (and probably carriage work) before east and west african fossil resins were introduced in germany and the US. The old literature says that germany and the US were the high paying customers for the fossil resin, so I don't know about other places- they may have stuck with resins from some other part of the world.

fossil copal was in great demand in the 1800s and probably some before that when it unseated sandarac.

I haven't run a sandarac varnish yet - sandarac is not as hard an is a little fragile, so it's sometimes mixed with rosin or run and then given a good dose of gum mastic (which is expensive).

I don't know which is harder to cook right -sandarac or congo copal. I don't want to ask steve or it might sound like back patting on my part celebrating that i've had solid luck running the fossil copal without torching it.

knock on wood, I haven't had a truly bad batch of varnish yet. I heated a couple of india resins a little dark for two different reasons, but the varnishes are good and they weren't exactly cooked to carbon - just cooked long while I was seeking to see if the resins would completely clear (the answer to that is no if the temperture is high - they will continue to fizz and foam as the resin is decomposing).

Cooking one batch of varnish 5 years ago and fighting to get some things where they needed to be (temperature to break the oil and then cooking the resins before adding oil) was strangely, a very big help in hitting the ground running.

The dirty filthy stuff in the fossil resins is a bit of a pain in the ass, though - it mocks ashed varnish, so when you first see it in the bottom of the pot and the resin is darkening (as it necessarily does just to get enough heat with copal) it can make you panic and think that it's actually ash.

Forgot to address the rosin thing. Rosin varnish looks great until it sees water for a while. It recovers OK, but it's not pretty like copal (copal must be what ducks put on their feathers), which literally sits with water on it and leaves not the slightest evidence it was ever wet as that water evaporates.

So, there is our rosin varnish -some of mine cooked five years ago, some cooked in the last couple of months - and there are various versions of rosin on violins and treatments to cook them for some duration and change them considerably, or possibly cooked raw resin or stuff like venetian turpentine down from a liquid to a final run rosin.

Sandarac was around - but the references I see to using it mention being used with shellac and maybe some type of gum resin (flexibilty). That means spirit varnish - shellac isn't referenced for oil varnishes.

Definitely plenty of history of spirit varnished violins, but I don't see mentions of copal varnishes in violins until well later.

Everyone wants to copy the early stuff, I guess. The low/middle decent violins (like into several thousand dollars from china) often have a spirit varnish. The higher production instruments with an oil varnish probably have phenolic or alkyd. Someone who makes violins in TN told bill that the higher end production violins (think like $6k or so?) use alkyd varnishes.

For the rest of the group here - this isn't related to the copal varnish - it's limed rosin (or pine resin with lime added to make the varnish harder, as pine resin itself leads to a very soft finish)

one thing that has struck me is the depths available visually. Limed resin is practically a utility finish because it would not be outdoor moisture tolerant, or same indoor, and plenty of more expensive natural resin varnishes are.

However, it's very light colored, so it may not be totally without future merit.

In terms of durability, one part water based finishes aren't that good and they're not as water tolerant as they claim (like leave a glass on one sweating and sitting for 6 hours and see what happens). Fossil copal varnish seems so far to be on the other end. It is completely indifferent to water by the time it's even half hard.

So, this utility finish, aside from not flowing out that well (limed rosin varnish - maybe we should refer to it as pine resin and linseed oil varnish, since that's what you may recognize the components as) is still a good finish and light years more durable than the strange expensive wax finishes that settle out to a sheen.

limed rosin maple - YouTube

This may not be immediately apparent as there is a shimmer and depth to this that you see in person. The phone's glare reduction may be a little confused by it. This is a nearly perfectly planed board with zero tearout and a tiny fraction of the finish absorption of a sanded surface, so there is not uneven finish uptake. the artifacts are directional in nature -it would look like it is moving as you walked past a table, much like figure.

But this is literally surplus pallet middle of the floor bog standard hard maple - flatsawn. The effect of this, I already gauged on very highly figured baked maple - it's overpowering, though taste on figured guitar next is not really a requirement, either.

I confirmed later that even a 220 grit linearly sanded surface will show these same artifacts - the varnish does not seem to suffer any loss of sheen on a sanded surface, it just takes more coats to start to build a gloss. (the little markered areas are just to see if different sealing methods make much of a difference - on maple, the answer is no - on woods that absorb more and get dark, the answer is a definite yes).

Brings an old snip that I took to mind (the tasteless guitar bit). I found some quartered khaya a few years ago and tried out various french polish methods on it.

https://i.imgur.com/coH3qfI.mp4

Two of the blanks look like this - varnish now obsoletes the french polishing that I was doing on guitars for the most part. The ribboned effect isn't unusual in guitars with mahogany, but the two that look like this are pretty garish and the ribboning has a weird kind of overlapping effect rather than looking like referee stripes.

One of the things missing since the factories took over furniture and then the whole back to the earth thing came in is finishes that have depth. None of the finishes shown here are very thick, either. they just look like they are a thicker gloss - they're sheer.

I think we may be seeing more and more home made varnishes like this with the new Low VOC standards pushing quality products out of the market.

Several high quality products rolled up and died while others changed their formulations. My prior all-time favorite Behlen's Rock Hard went to a different solvent package. While the varnish was easier to use overall, the new solvents gave me ripping headaches. Out the door it went.

the VOC limitations are a farce. can't remember what I've said in threads here, but what happens is that (apologies if you've already looked into what's in the finishes) the finish companies go to some alternative solvent that's gotten a prior waiver from the EPA. some of them are much worse as they have the same VOC content (just legally allowed to say they don't) and are harder on ozone and such, and are much more irritating.

The quality of how they flow out will be different and you'll feel strange.

Too, at some point, behlen's varnish was a varnish. It's just polyurethane at this point with the price tag of alkyd or tung oil / phenolic varnishes.

We haven't had hard varnishes for furniture for a very long time because the market for varnishes is in flexible finishes that are either not water tolerant (alkyds) or that are (tung/phenolic). I guess it's harder to cook these varnishes as phenolic resin is findable on alibaba for $3 a kg or so in different melting points. I'm sure it's dangerous to make, though - I see a lot of literature about phenol poisoning.

the trouble for the hobby if everyone wants to start making these harder furniture varnishes like copal will be the supply of it on a fossil basis is just almost nonexistent. I've got ten pounds of congo copal resin from wood finishing enterprises, it was about $650 or $660 or something - and I don't really know of any other varnishes that you can get that are hard other than baltic amber. That'll make a dark varnish and as much as there's not room to work much higher in temperature with copal, baltic amber can dabble around the autoignition point to melt.

it's too bad -it's a lost art, and it's one thing to get a workable varnish as I've done. There's a lot more to figure out, like how to get it to have flowout qualities that would make it more dreamy to brush whereas right now it's good, but I think it could be better.