Shellac

[ARW123]

The battle with the deck beams continues and whilst trying to minimise the desecration of original components I was scratching off the old, crazed, dark, matt varnish before repairing them. It had been explained to me that this was the orignal varnish and that is what happened to it.

I had tried to remove it with a heat gun in the past but it just formed a gloopy and VERY sticky lump. The solution was to use a freshly sharpened cabinet maker's scraper and it flecks off as a powder - but still the penny didn't drop.

It is only just today as I was cleaning up the beam shelf coated with the same stuff that I saw vestages of a purplish colour and I realised - this is b***dy shellac!

Clearly all of the "not so visible" parts had originally been coated in the stuff, oddly in areas where you might expect to find damp conditions (and rot) - such as the beam shelf - there is no rot; even where there have been obvious leaks around the deck near the chain plates. In these locations the knees have suffered but not, it would appear the beam shelf underneath.

So this waffle brings me to the question "does shellac have any anti-fungal properties?". Cursory research on the internet doesn't seem to reveal anything, but why would the original builders use shellac in preference to varnish?

[pcford]

Shellac was often used in traditional boats. It dries very fast. Though delicate, it was used in areas which are unexposed

[ARW123]

Yes, but other than keeping the air out, does it work any better than varnish?

Incidentally some would seem to question its delicacy, citing that it will withstand many hours submersion in water without undue effect...

[pcford]

Yes, but other than keeping the air out, does it work any better than varnish?

Incidentally some would seem to question its delicacy, citing that it will withstand many hours submersion in water without undue effect...

As I said, it dries quicker than varnish; in that regard it is better than varnish. In general it is not more durable than varnish.

Shellac was used between layers for sealing double planking.

I recall it being used on a Canadian Forestry boat on the overhead.

Alcohol will strip it.

[David G]

ARW - I guess I haven't been following your battle with deck beams, so I can't comment directly on your situation. I'll just say - I love shellac, and have used it for years for a variety of applications. For some things, it better than spar varnish. For some, it's as good. It does have some weaknesses, however. Compared to spar varnish, it doesn't hold up to abrasion or impact as well. Also iffy to use it anywhere where it might get alcohol splashed on it, 'cause alcohol dissolves it. As Pat said, it was used by a lot of savvy trad boat builders, cause it seals well, dries fast, is easily manipulated as to consistency for various tasks (like adding additives to epoxy), and wasn't that expensive. Based strictly on my personal anecdotal evidence over the years, I suspect it does have some sort of anti-fungal properies. Or, maybe the small molecular size and volatility of the solvent results in better penetration/seal. I just know shellaced parts don't seem to want to rot. One of the nice things is how easy it is to clean up with alcohol. To the extent that I understand your task, this should make your life simpler, perhaps.

[ARW123]

David, its not something I'd thought about, but having "wasted" 2-3 weeks recoating time for varnishing beams and tabernacle - its drying time is very attractive IF it can be relied upon to be more or less as good as varnish. The stuff I'm removing has lasted a century so the shellac I would put on I comfortably predict will outlast me!!

The trouble is I cannot remove too many beams for fear losing the shape so the progress of the step by step phase is being governed by the varnishing time of the components - 6 coats each (doing it out of the boat is easier and I believe more thorough as a result).

[villtur]

It probably isn´t very poisonous since it is edible.

[keith66]

I beleive the stuff normally used was Copal varnish which is a shellac based varnish, a couple of old boats i have worked on have been coated with it & it seems to last well.

[Scot L T]

Shellac is a resin gathered from the lac bug (most often from India and area) and soluble in alcohol but is insoluble in turpentine. Copal is a plant resin (most often a mesoamerica found plant) and is usually combined with a oil through the means of heat to create a varnish.

Both are excellent as an "isolating varnish" between layers (one example: seal the wood, apply shellac or copal varnish, finish with oil varnish of choice.) but tend to crack and darken over time. Copal is a harder surface than shellac and these days, much more expensive as the resin it is getting quite rare and hard to come by.

One reason to use shellac is the ease with which it is to repair. It is also non-toxic, is surprisingly moisture resistant (the Maine Guides loved to use it on the bottom for their canoes, it held up well, slipped easily over the river rocks when needed and was very quick to repair when needed) and can be removed with almost any alcohol. I wouldn't be without it in my woodworking shop.

[Lew Barrett]

We all love shellac, and sooner or later learn where it works for us. Since this has been a love fest for the stuff, I'll put in the only negative I can think of based on my experience with it. As a sealer and first (or first course) coat it is really great stuff to have around. However, it's UV properties (or lac of them.....get it? it's a joke) can be an issue if you seal with it for outdoor uses and then cover with a clear finish, even one with high UV resistence such as premium varnish. You won't discover this right away, but if that varnish breaks down someday (as it will usually do) the resulting combination is harder to strip than either one alone. (that is varnish or shellac),

So I don't use shellac as a varnish sealer (or as an outdoor finish) but do use it where fast dry time and good general sealing is needed. Perfect for sealing wood between say, worm shoe and keel, or a place where you need to use bedding compound and would like a first coat sealer.

So, we all like shellac, plus it smells the best.

[ARW123]

Thanks for input - so the general consensus is I could use it under the deck level (no UV), which is good as that will seriously cut down the time I have been waiting in between varnish coats.

[ARW123]

OK, so armed with your advice found the rusty tin with the shellac chips in Father's workshop. Speaking with Mother, there's every likelihood this is Grandfather's so that makes it about 80+ years old...going to be an experiment, this one!
http://www.means2.com/Assets/Corsair/Shellac.jpg

Firstly using a pestle & mortar, spent about 20 minutes grinding and made enough for about a couple of egg cups. Left for a day stirring & heating every now & then to disolve it all. I tried 6 or so coats on an offcut and really pushed the recoat time - sometimes within the hour. Staggering stuff, and seems on the face of it really forgiving. It only complained when it was put too close to the woodburner and then it blistered a bit - but that is operator error not the fault of the substance. Bouyed up by this I tried 3 coats on a couple of places on the the internal planking:
http://www.means2.com/Assets/Corsair/Shellac_Forepeak.jpg

(the test application on the right). Despite its age, application and drying don't seem unduly affected...at the moment!

David G; the deck beam saga has not been overtly discussed on this forum, but I have had to remove the whole foredeck, repair & replace numerous beams:
http://www.means2.com/Assets/Corsair/New_Beam_Mock_Up.jpg

Its fairly clear which have been replaced and repaired, the main issue is that not too many can be removed at a time without concern about losing the shape. (The ratchet strap is there because even though I braced the beam shelf before removing the original of the new light-coloured right hand beam, it sprang by about 3/8"). Choosing to varnish all beams out of the boat for reasons of convenience and 100% coverage, means that the process is damned slow - hence my interest in the shellac.

http://rcc-corsair.blogspot.com/

[Chris Setzler]

If I understand you correctly, you heated 80 year old shellac until it was a liquid and applied that. I used shellac in my custom furniture business and dissolved the flacks in denatured alcohol. The concentration is usually specified as pounds cut. Two pounds of shellac in a gallon of alcohol is a 2lb. cut. I have always been told both mixed and flake shellac have a limited shelf life meaning if it's too old, it generally won't dry.

I have never heard of your process, but would like to hear any comments on it.

[jonboy]

Shellac is so fast drying I put on maybe five coats in an hour, as long as it's warm enough... if too cold it can bloom, ...it's penetrative if the first coats are applied thinly enough, and cut back with an alcohol-damp rag, ...in fact the french-polish method is to put it on with a fad, a ball of cotton wool inside a folded rag, opened every now and then and recharged with fresh lac. is the best way to get the classic finish... much quicker with a brush though on a boat where antique furniture quality finish is not so critical, I would ladle it on, metaphorically speaking.

It's initial penetration is what gives the anti-fungal action I suspect as it is such a sealant.
Don't let anyone tell you otherwise... IT IS NOT durable in water... the classic wine glass / coffee cup ring on furniture is the reason we have the modern finishes... It's ok, but don't think it is up to the oil or synthetic varnishes....great for interiors, a super finish in areas not so heavily used, but it is a relatively fragile surface... the beauty is it is easily re-touched or repaired with a little pure alcohol or more of the made up polish.

With regard to the large chunks in the photos, put them in a strong cloth or hessian sack and pound the proverbial out of them with a lump hammer.... the smaller the particle the faster the chemical reaction...my usual working viscosity is with flake shellac, poured into a large jam jar and the alcohol poured in until it just covers the flakes, a bit more maybe and left for a few hours with the occasional shake...... need it thinner, dilute, thicker, leave the lid off a day or two...

[ARW123]

No, apologies if it's not clear, the ground shellac dust was dissolved in meths, as per the approved method - I will admit to a rather less scientific cutting ratio................!

Jonboy; when really pushing the recoat interval there was mild blooming, with regard to breaking the chunks down, later experimentation found that a coffee grinder saved time and aching arms. As far as finish is concerned, mirror finish is not really required as it's as dark as Hades in the forepeak!!

[Lew Barrett]

Well it all looks just great! It seems a lavish way to treat the boat, but it also looks like you'll be able to eat lunch straight off of the bilge when you're done.

[jonboy]

No, apologies if it's not clear, the ground shellac dust was dissolved in meths, as per the approved method - I will admit to a rather less scientific cutting ratio................!

Jonboy; when really pushing the recoat interval there was mild blooming, with regard to breaking the chunks down, later experimentation found that a coffee grinder saved time and aching arms. As far as finish is concerned, mirror finish is not really required as it's as dark as Hades in the forepeak!!

working inside a boat is always going to be less than ideal unless it's out of the water and dry...above 20º C and RH of less than 60% is ideal, but the blooming won't be from too short a re-coat interval......(I am sure it's too cool.) if thats the case you'll feel the drag of the new coat over the too-fresh previous coat.
Coffee grinder ? go up a grade to a kitchen liquidiser at least.. I got the chance at a load of big chunks like you have and put them through the garden waste shredder... B an D kit, nothing industrial... handles up to 30mm dia. prunings.... worked great but a fair bit of wastage... took minutes to do about twenty kgs though.